Medical Diet and Health

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bobze

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When studying the effects of various interventions on human health, it is notoriously difficult to glean actionable information from any one single scientific study. Often these are observational studies that are subject to many confounding factors and limited by small sample sizes, poorly controlled conditions, and short observation periods. Even well-controlled, randomized clinical trials can often reach opposing conclusions.

We can reach better conclusions, however, by performing a systematic literature review: examining the scientific literature as a whole by using strict criteria to select the highest quality studies and evaluating the results of the all of the studies as a whole. Although there may be individual studies within the review that support either side of an assertion, if a large majority of the studies support one side of an argument, we can be much more confident about their conclusions.

The 2007 report, Food, Nutrition, Physical Activity, and the Prevention of Cancer by the World Cancer Research Fund and American Institute for Cancer Research does just this. I will summarize the relevant findings of the review below. The full report is available here: http://www.dietandcancerreport.org/

Because obesity is an established cause of cancer, the report examined the risk factors for weight gain, overweight, obesity. The systematic literature review of this area covered 207 publications investigating the determinants of weight gain, overweight and obesity. The report concludes:

"The epidemiological evidence on physical activity is substantial and consistent. There is robust mechanistic evidence, particularly in relation to its impact on appetite regulation and energy balance. Overall, the evidence that all types of physical activity protect against weight gain, overweight, and obesity is convincing. It has this effect by promoting appropriate energy intake. Conversely, the evidence can be interpreted as showing that sedentary living is a cause of weight gain, overweight, and obesity."

The panel gives the evidence linking physical activity to a decreased risk of weight gain, overweight and obesity its highest ranking of convincing. The panel ranks the strength of evidence linking energy-dense foods, sugary drinks, and fast food to an increased risk of weight gain, overweight and obesity as probable.

Furthermore, while Siv has claimed that changes to appetite that accompany physical activity cancel the effects of exercise, the report claims otherwise:

"Control [of appetite] seems to be least effective at relatively low levels of physical activity, meaning that sedentary people tend to gain weight more readily than active people. Conversely, although high levels of physical activity increase energy requirements and appetite, the likelihood of consuming more than is needed is lower."

Therefore, although some may be able to produce studies showing otherwise, the preponderance of high quality scientific evidence strongly supports the assertion that physical activity can prevent weight gain, overweight and obesity.

Since this topic was originally on cancer, I will quote the panel's conclusions about the effects of sugar consumption on the risk for cancer:
"The evidence is hard to interpret. There is limited evidence suggesting that sugar is a cause of colorectal cancer."

This does not mean that there is convincing evidence that sugar is not a cause of cancer. Rather, the report concludes that there is not sufficient high quality evidence to reach a solid conclusion.

Good post!
 

Siv

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Re: Cancer man-made or junk science?

you know i specifically used that study for appetite suppression.

but if you want something with more significance, try this one: http://www.annals.org/content/140/10/769.full

if you want something really rigid (heavily controlled inpatient vs. outpatient), then this is interesting: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC333231/
You claimed that Atkins weight loss was mostly water loss, so I thought your links would support that. Anyway lets look at what you have now ...

Ok, this is what I have from your first study -
Changes in total body water explained most of the change in fat-free mass in both groups. The expected mean change in total body water was −2.4 kg (CI, −2.9 to −2.0 kg) in the low-carbohydrate diet group and −1.8 kg (CI, −2.3 to −1.3 kg) in the low-fat diet group (mean difference, −0.6 kg [CI, −1.3 to 0 kg]; P = 0.052). However, the low-carbohydrate diet group lost a greater amount of total body water in the first 2 weeks of the study than did the low-fat diet group (−1.1 kg versus −0.5 kg; mean difference, −0.6 kg [CI, −1.0 to −0.2 kg]).
The differences are again very marginal. - 2.4 kg vs 1.8 kg and 1.1 vs 0.6 kg.
Come on, its not even statistically significant, IMO.

And lets look at the actual results from that study, shall we ?
Results: A greater proportion of the low-carbohydrate diet group than the low-fat diet group completed the study (76% vs. 57%; P = 0.02). At 24 weeks, weight loss was greater in the low-carbohydrate diet group than in the low-fat diet group (mean change, −12.9% vs. −6.7%; P < 0.001). Patients in both groups lost substantially more fat mass (change, −9.4 kg with the low-carbohydrate diet vs. −4.8 kg with the low-fat diet) than fat-free mass (change, −3.3 kg vs. −2.4 kg, respectively). Compared with recipients of the low-fat diet, recipients of the low-carbohydrate diet had greater decreases in serum triglyceride levels (change, −0.84 mmol/L vs. −0.31 mmol/L [−74.2 mg/dL vs. −27.9 mg/dL]; P = 0.004) and greater increases in high-density lipoprotein cholesterol levels (0.14 mmol/L vs. −0.04 mmol/L [5.5 mg/dL vs. −1.6 mg/dL]; P < 0.001). Changes in low-density lipoprotein cholesterol level did not differ statistically (0.04 mmol/L [1.6 mg/dL] with the low-carbohydrate diet and −0.19 mmol/L [−7.4 mg/dL] with the low-fat diet; P = 0.2). Minor adverse effects were more frequent in the low-carbohydrate diet group.
Minor adverse effects at the initial stages aside (constipation, headache and the likes), the low carb results were spectacular !

Ok, your second study ... the period is for 50 days total, but in 3 10-day periods. That is very short, IMO. Even 24 weeks in the prev study were short but at least not as short as 50 days. So I dont really find anything significance in the very short term water weight loss.

In any case, the reason for the water loss has also been explained very well b Taubes and others. Carbs make people retain water, as I explained.
 

Siv

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When studying the effects of various interventions on human health, it is notoriously difficult to glean actionable information from any one single scientific study. Often these are observational studies that are subject to many confounding factors and limited by small sample sizes, poorly controlled conditions, and short observation periods. Even well-controlled, randomized clinical trials can often reach opposing conclusions.
That is true. But the whole problem with nutrition science (if you can call it science) is how people stretch epidemiological data to support their arguments.
Epidemiological data faces huge problems when it tries to take the place of scientific trials.

Here's an award winning article from Gary Taubes in the National Association of Science Writers on the limitations of epidemiology.
http://www.nasw.org/awards/1996/96Taubesarticle.htm

We can reach better conclusions, however, by performing a systematic literature review: examining the scientific literature as a whole by using strict criteria to select the highest quality studies and evaluating the results of the all of the studies as a whole. Although there may be individual studies within the review that support either side of an assertion, if a large majority of the studies support one side of an argument, we can be much more confident about their conclusions.

The 2007 report, Food, Nutrition, Physical Activity, and the Prevention of Cancer by the World Cancer Research Fund and American Institute for Cancer Research does just this. I will summarize the relevant findings of the review below. The full report is available here: http://www.dietandcancerreport.org/
Problem again, is that it is an epidemiological report. A meta analysis, but one based on epidemiological data nonetheless.

Therefore, although some may be able to produce studies showing otherwise, the preponderance of high quality scientific evidence strongly supports the assertion that physical activity can prevent weight gain, overweight and obesity.
High quality evidence ? No.
I will go through the link in detail later when I have time.

Meanwhile, people who have tried to actual clinical trials find quite the opposite results.

Dr. Timothy Church for eg.
At http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004515

This was a 6 month study. But the surprising finding was that, the control group had a better outcome than the high exercise group :smile:
The primary finding from this large exercise intervention trial in postmenopausal women is that the difference between actual weight loss and predicted weight loss (compensation) increases with exercise dose. We confirmed the findings of previous studies that a relatively high dose of exercise (12 KKW or 194 minutes per week) results in compensatory mechanisms that attenuate weight loss in previously sedentary women. However, a dose of exercise consistent with the exercise prescription for general health (8 KKW or 136 minutes per week) did not result in compensation as the actual weight loss closely matched the predicted weight loss. An exercise dose of 4 KKW (72 minutes per week) also resulted in weight loss that slightly exceeded the predicted weight loss. Our findings are important because most exercise guidelines for weight loss recommend 200–300 minutes per week and we provide evidence that this amount of exercise induces compensation that results in significantly less weight loss than predicted.
So 10-15 mins exercise per day (the most sedentary of the 3 groups) seems the most beneficial !

Please also see the Terry Wilkin study re: childhood obesity that I posted earlier.
http://adc.bmj.com/content/early/200...35012.abstract [Broken]
There were no associations between physical activity and changes in any measure of body mass or fatness over time in either sex (e.g. BMI-SDS: r=-0.02 p=0.76). However, there was a small-to-moderate inverse association between physical activity and change in composite metabolic score (r=-0.19, p<0.01). Mixed effects modeling showed that the improvement in metabolic score among the more active compared to the less active children was linear with time (-0.08 z-scores/year, p=0.001). Again, this is an actual trial, not an epidemiological analysis.

Other studies are mentioned in this article
http://www.cbc.ca/health/story/2009/05/07/school-exercise-obesity-child.html [Broken]

Rather than relying on epidemiological evidence, if you end up doing actual studies, however faulty they may be, the results are far more accurate and practical.

Blaming our sedentary lifestyles for obesity without any actual evidence is something for which Jean Mayer requires the most credit. And he promoted his pro-exercise message with a religious zeal like a moral crusade.

People are exercising far more today than they did several decades ago. So, has the obesity declined or gone up ?!
 
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bobze

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That is true. But the whole problem with nutrition science (if you can call it science) is how people stretch epidemiological data to support their arguments.
Epidemiological data faces huge problems when it tries to take the place of scientific trials.

Here's an award winning article from Gary Taubes in the National Association of Science Writers on the limitations of epidemiology.
http://www.nasw.org/awards/1996/96Taubesarticle.htm

Problem again, is that it is an epidemiological report. A meta analysis, but one based on epidemiological data nonetheless.

High quality evidence ? No.
I will go through the link in detail later when I have time.

Meanwhile, people who have tried to actual clinical trials find quite the opposite results.

Dr. Timothy Church for eg.
At http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004515

This was a 6 month study. But the surprising finding was that, the control group had a better outcome than the high exercise group :smile:
So 10-15 mins exercise per day (the most sedentary of the 3 groups) seems the most beneficial !

Please also see the Terry Wilkin study re: childhood obesity that I posted earlier.
http://adc.bmj.com/content/early/200...35012.abstract [Broken]
There were no associations between physical activity and changes in any measure of body mass or fatness over time in either sex (e.g. BMI-SDS: r=-0.02 p=0.76). However, there was a small-to-moderate inverse association between physical activity and change in composite metabolic score (r=-0.19, p<0.01). Mixed effects modeling showed that the improvement in metabolic score among the more active compared to the less active children was linear with time (-0.08 z-scores/year, p=0.001). Again, this is an actual trial, not an epidemiological analysis.

Other studies are mentioned in this article
http://www.cbc.ca/health/story/2009/05/07/school-exercise-obesity-child.html [Broken]

Rather than relying on epidemiological evidence, if you end up doing actual studies, however faulty they may be, the results are far more accurate and practical.

Blaming our sedentary lifestyles for obesity without any actual evidence is something for which Jean Mayer requires the most credit. And he promoted his pro-exercise message with a religious zeal like a moral crusade.

People are exercising far more today than they did several decades ago. So, has the obesity declined or gone up ?!
3 quick points because I'm running late. Firstly, as Ygg pointed out Systematic/Meta-Reviews>>>>>> case-controls, cohorts or any other primary literature findings. Because, systematic reviews offer to us a summation of findings from many different sources, we are able to derive trends in them. As Ygg's review also points out that trend is to show that when you exercise a long with watching your diet you lose weight.

Secondly to your underlined sentence above. Many people do exercise more, however people also eat larger meal portions than they did in say the 50's or 60's. A serving of meat for most people should be about a deck of cards, when was the last time in America you've seen a correct portion of meat on the menu? Being a medical student, I eat out a lot--Restaurants take the "American dream" (more for less) approach to advertising. In fact, that approach to advertising is everywhere around us in the food industry--"More for less".

And finally, can you propose a biochemical mechanism whereby different types of carbohydrates are preferentially stored as fat? Without being able to show this any evidence of differential carb storage is anecdotal and more likely attributed to confounding factors (even if the confounder is a food specific factor, for example something else in the food with those "bad" carbs which promotes more fat storage)


Thanks

Edit: Your BMJ link isn't working by the way.
 
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Siv

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3 quick points because I'm running late. Firstly, as Ygg pointed out Systematic/Meta-Reviews>>>>>> case-controls, cohorts or any other primary literature findings. Because, systematic reviews offer to us a summation of findings from many different sources, we are able to derive trends in them. As Ygg's review also points out that trend is to show that when you exercise a long with watching your diet you lose weight.
Unfortunately, whether its one study or a meta analysis, if its epidemeliogical data, its pretty much often always misleading. Did you read the link I posted with Taubes award winning article on that ?

And finally, can you propose a biochemical mechanism whereby different types of carbohydrates are preferentially stored as fat? Without being able to show this any evidence of differential carb storage is anecdotal and more likely attributed to confounding factors (even if the confounder is a food specific factor, for example something else in the food with those "bad" carbs which promotes more fat storage)
Its been beautifully explained, by Taubes and others. Carbs drive insulin drive fat storage (and other bad things). Read the book, its hard for me to summarize an entire book with tons of studies into one post. As I was telling someone else on this forum, the book is like pubmed, so its hard reading. But the plethora of evidence is worth it.

Your BMJ link isn't working by the way.
Oops, sorry. It was working yesterday. Let me check.
 
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Not sure why there seems to be so much sure footed posturing in this thread. Obesity - is evidently a spectrum disorder - not a single disease. And as a spectrum disorder will have a spectrum of causes. Until we are in a position to ascribe the different causes of obesity to their respective populations - none of these studies will be in a position to make specific claims. All that remains is statistical correlation and postulation.
 
Not sure why there seems to be so much sure footed posturing in this thread. Obesity - is evidently a spectrum disorder - not a single disease. And as a spectrum disorder will have a spectrum of causes. Until we are in a position to ascribe the different causes of obesity to their respective populations - none of these studies will be in a position to make specific claims. All that remains is statistical correlation and postulation.
i suppose you could make the same argument about alcoholism and drug use, but it's not helpful for explaining what is going on in the majority of the population. it's really just excuse-making for a population whose primary problem is they enjoy continuing their behavior more than they dislike the negative side effects.

the really interesting thing about this "disease" of obesity is that if you take away their freedoms and only allow them to consume a healthy amount of calories, they will lose weight.
 
Re: Cancer man-made or junk science?

You claimed that Atkins weight loss was mostly water loss, so I thought your links would support that. Anyway lets look at what you have now ...

Ok, this is what I have from your first study - The differences are again very marginal. - 2.4 kg vs 1.8 kg and 1.1 vs 0.6 kg.
Come on, its not even statistically significant, IMO.

And lets look at the actual results from that study, shall we ? Minor adverse effects at the initial stages aside (constipation, headache and the likes), the low carb results were spectacular !

Ok, your second study ... the period is for 50 days total, but in 3 10-day periods. That is very short, IMO. Even 24 weeks in the prev study were short but at least not as short as 50 days. So I dont really find anything significance in the very short term water weight loss.

In any case, the reason for the water loss has also been explained very well b Taubes and others. Carbs make people retain water, as I explained.
where did you explain that carbs make people retain water?

and yes, low-carb diets (temporary diets for fat reduction(my fave would be the protein-sparing modified fast, with almost no fat at all)) can be spectacular for a number of reasons. as mentioned before, ketosis can have a significant appetite-suppressive effect, and this makes it easier for people stay on the diet. it also makes it easier for them to control their intake and consume fewer calories. and that is the important point i'm trying to get across. there is nothing magical about carbs making you fat, it's an excess of calories consumed that makes you fat.

and look again at the inpatient study. i think what you will see is that when you actually control what people eat (they can't cheat by sneaking candy and lying about it - skewing your results), fat loss on either a low or med. carb diet is similar.

the other thing to remember is that these studies are primarily about dieting for fat loss, and really don't make a case for eating a ketotic diet on a chronic basis. for that, go look up the papers where they mention the problems with keeping epilepsy patients on keto diets.
 
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Agree totally Proton - its the only approach that works. I just find it strange that people want to ascribe it to all these different specific things - whats the point. We dont know - but as you say - what we do know is that if you limit intake and expend more energy - its a solution - irresepective of the specifics of the problem.

Of course people dont want to hear that because it means that they can control the problem - it just takes a heck of a lot of effort and fighting against what our evolutionary biology has dictated we do! In a world of scarcity it was wise to crave fatty sugary food! The scenario has changed!

Manufacturers also dont want to hear it because they cant make money out of people by selling supplements, plans, pills etc

I always am amazed at the amount of money spent on diabetes and CV research - when in fact if we changed attitudes at a young age - we could prevent themajority of these diseases even occuring. Prevention is ultimate, cure is an expensive band aid.
 
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bobze

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Unfortunately, whether its one study or a meta analysis, if its epidemeliogical data, its pretty much often always misleading. Did you read the link I posted with Taubes award winning article on that ?

Its been beautifully explained, by Taubes and others. Carbs drive insulin drive fat storage (and other bad things). Read the book, its hard for me to summarize an entire book with tons of studies into one post. As I was telling someone else on this forum, the book is like pubmed, so its hard reading. But the plethora of evidence is worth it.

Oops, sorry. It was working yesterday. Let me check.
No I don't mean how carbohydrates drive insulin regulation and vise-versa. I'm well versed in that.

However, you claimed that various types of carbohydrates promoted this more than others, if I'm remembering correctly (a couple pages back I believe).

What I was asking for is, what is the biochemical mechanism or hypothesis that would explain this. Otherwise, as I pointed out, its just as likely that other confounding factors associated with those 'types of carbs' are the culprit in the up-regulation of insulin and not the 'type' of carb itself.

For example. You claimed that HFCS (a mix of fructose and glucose) is 'worse' for you than sucrose (fructose and glucose). What is the proposed biochemical mechanism for this? And on what basis do you discard the hypothesis that foods with HFCS may contain another factor that promotes obesity over sucrose based ones (if it does at all)?
 
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Ygggdrasil

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That is true. But the whole problem with nutrition science (if you can call it science) is how people stretch epidemiological data to support their arguments.
Epidemiological data faces huge problems when it tries to take the place of scientific trials.

Here's an award winning article from Gary Taubes in the National Association of Science Writers on the limitations of epidemiology.
http://www.nasw.org/awards/1996/96Taubesarticle.htm

Problem again, is that it is an epidemiological report. A meta analysis, but one based on epidemiological data nonetheless.
You would have a valid point if the report relied solely on epidemiologial evidence. But, it does not. Of the studies considered linking physical activity to weight maintenance and change, the panel considered 17 randomized controlled trials versus 62 consort studies. No doubt, the experts on the panel gave more consideration to the randomized trials than the consort studies.

For example, we can consider the studies that examined the effects of total physical activity on weight maintenance and change in adults. In this category, there were three randomized controlled trials and 16 consort studies. Two of the randomized controlled trials showed positive effects of physical activities while one of the trials showed no effect. All of the 16 consort studies in this area showed a positive effect. The citations for the three randomized trials are below:
  • Schmitz KH, Jensen MD, Kugler KC, et al. Strength training for obesity prevention in midlife women. Int J Obes 2003;27:326-33.
  • Borg P, Kukkonen-Harjula K, Fogelholm M, et al. Effects of walking or resistance training on weight loss maintenance in obese, middle-aged men: a randomized trial. Int J Obes 2002;26:676-83.
  • Fogelholm M, Kukkonen-Harjula K, Nenonen A, et al. Effects of walking training on weight maintenance after a very-low-energy diet in premenopausal obese women: a randomized controlled trial. Arch Intern Med 2000;160:2177-84.

As I said before, some studies will show no effect and some studies will show a positive effect. However, considering the evidence as a whole shows that the bulk of the evidence points to physical activity as a protective factor against weight gain.

Meanwhile, people who have tried to actual clinical trials find quite the opposite results.

Dr. Timothy Church for eg.
At http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004515

This was a 6 month study. But the surprising finding was that, the control group had a better outcome than the high exercise group :smile:
So 10-15 mins exercise per day (the most sedentary of the 3 groups) seems the most beneficial !
I'm not so sure you're reading the study correctly. Look at at the data in http://www.plosone.org/article/showImageLarge.action?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0004515.g003&representation=PNG_L [Broken]. While the control group showed a weight change of -0.9 kg, the 4 kcal/kg/week exercise group showed a weight change of -1.4 kg, the 8 kcal/kg/week exercise group showed a weight change of -2.1 kg, and the 12 kcal/kg/week exercise group showed a weight change of -1.5 kcal/kg/week. All three experimental groups showed more weight loss than the control group. The authors are merely saying that as exercise dose increases, you get decreasing returns on weight loss (due to the compensatory increases in appetite that you discussed earlier). However, this compensation does not lead to any of the exercise groups to show less weight loss than the control group.
 
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Siv

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Ok, read this news article yesterday.
http://www.dailymail.co.uk/health/article-1323758/Can-cutting-Carbohydrates-diet-make-live-longer.html?ito=feeds-newsxml
Can cutting carbohydrates from your diet make you live longer?
Professor Cynthia Kenyon, whom many experts believe should win the Nobel Prize for her research into ageing, has discovered that the carbohydrates we eat — from bananas and potatoes to bread, pasta, biscuits and cakes — directly affect two key genes that govern youthfulness and longevity.
Scientists already knew how to make laboratory animals live longer and healthier lives — you just cut back their calories to about three-quarters of their normal amount.

It’s not a practical solution for humans, because you feel cold and hungry all the time.

But what Professor Kenyon found out was why *drastically reducing calories has such a remarkable effect.

She discovered that it changed the way two crucial genes behaved. It turned down the gene that controls insulin, which in turn switched on another gene, which in turn switched on another gene, which acted like an elixir of life.

We jokingly called the first gene the Grim Reaper because when it’s switched on, the lifespan is fairly short,’ she explains.
Discovering the Grim Reaper gene has prompted the professor to *dramatically alter her own diet, *cutting right back on carbohydrates. That’s because carbs make your body produce more insulin (to mop up the extra blood sugar carbs *produce); and more insulin means a more active Grim Reaper.
One clue came from a small remote community of dwarves living in northern Ecuador who are cancer-free. They are missing the part of the Grim Reaper gene that controls a hormone called insulin-like growth factor. The downside is they only grow to 4ft tall because the hormone is needed for growth.

But this missing bit of the Grim Reaper gene also means they don’t develop cancer and are less likely to suffer from heart disease or obesity.

Professor Jeff Holly, who specialises in insulin-like growth factor, confirms that it is linked to cancer of the prostate, breast and colon.

In fact raised insulin levels, triggered by high carbohydrate *consumption, could be what *connects many of our big killers.
One way to reduce insulin levels is to exercise, which makes you more sensitive to it, which in turn means you need less of it. It also gives another health benefit in a surprising way. Exercise actually increases the level of damaging free radicals which stimulates the body to produce more protective anti-oxidants.

So should we all be trying to cut back on carbs to reduce our insulin levels?

It is a suggestion that flies in the face of 30 years of health advice to have a lower fat intake and eat plenty of long-lasting complex carbo*hydrates to keep the body supplied with energy.
 

Siv

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For example, we can consider the studies that examined the effects of total physical activity on weight maintenance and change in adults. In this category, there were three randomized controlled trials and 16 consort studies. Two of the randomized controlled trials showed positive effects of physical activities while one of the trials showed no effect. All of the 16 consort studies in this area showed a positive effect. The citations for the three randomized trials are below:
  • Schmitz KH, Jensen MD, Kugler KC, et al. Strength training for obesity prevention in midlife women. Int J Obes 2003;27:326-33.
  • Borg P, Kukkonen-Harjula K, Fogelholm M, et al. Effects of walking or resistance training on weight loss maintenance in obese, middle-aged men: a randomized trial. Int J Obes 2002;26:676-83.
  • Fogelholm M, Kukkonen-Harjula K, Nenonen A, et al. Effects of walking training on weight maintenance after a very-low-energy diet in premenopausal obese women: a randomized controlled trial. Arch Intern Med 2000;160:2177-84.

As I said before, some studies will show no effect and some studies will show a positive effect. However, considering the evidence as a whole shows that the bulk of the evidence points to physical activity as a protective factor against weight gain.
Hmm. Exercise definitely has other benefits and I have admitted that. It improves your insulin resistance, among other things, which could definitely help you reduce weight.
What I dont believe, and what I dont think there is evidence for is the simplistic calories in calories out interpretation of saying that the more you exercise, the more calories out and therefore you will lose weight. Thats nonsense. Because the body will compensate by making you hungrier. We have evolved a very complicated system over millions of years to preserve homeostasis.

I'm not so sure you're reading the study correctly. Look at at the data in http://www.plosone.org/article/showImageLarge.action?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0004515.g003&representation=PNG_L [Broken]. While the control group showed a weight change of -0.9 kg, the 4 kcal/kg/week exercise group showed a weight change of -1.4 kg, the 8 kcal/kg/week exercise group showed a weight change of -2.1 kg, and the 12 kcal/kg/week exercise group showed a weight change of -1.5 kcal/kg/week. All three experimental groups showed more weight loss than the control group. The authors are merely saying that as exercise dose increases, you get decreasing returns on weight loss (due to the compensatory increases in appetite that you discussed earlier). However, this compensation does not lead to any of the exercise groups to show less weight loss than the control group.
Here's the chart
There is a marginal reduction, I agree. But its marginal.
And the more the intensity increases the lesser it is. Which kind of negates the simplistic calories in calories out theory.
Plus how are you controlling for the other improvements due to exercise, like insulin resistance ?

Have you read this article from Gary Taubes ? You dont seem the kind of person who dismisses folks without reading the evidence, so please do read it.
http://nymag.com/news/sports/38001/
There is other evidence too, let me try and dig it out. Wish I had more time.
 

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Siv

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No I don't mean how carbohydrates drive insulin regulation and vise-versa. I'm well versed in that.
Great. So you do realize the truth in that.

However, you claimed that various types of carbohydrates promoted this more than others, if I'm remembering correctly (a couple pages back I believe).

What I was asking for is, what is the biochemical mechanism or hypothesis that would explain this. Otherwise, as I pointed out, its just as likely that other confounding factors associated with those 'types of carbs' are the culprit in the up-regulation of insulin and not the 'type' of carb itself.

For example. You claimed that HFCS (a mix of fructose and glucose) is 'worse' for you than sucrose (fructose and glucose). What is the proposed biochemical mechanism for this? And on what basis do you discard the hypothesis that foods with HFCS may contain another factor that promotes obesity over sucrose based ones (if it does at all)?
Here are my posts. They present what I said and some of the studies. Please read them.
https://www.physicsforums.com/showpost.php?p=2948044&postcount=17
https://www.physicsforums.com/showpost.php?p=2941054&postcount=2
https://www.physicsforums.com/showpost.php?p=2943978&postcount=13
 

Ygggdrasil

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Hmm. Exercise definitely has other benefits and I have admitted that. It improves your insulin resistance, among other things, which could definitely help you reduce weight.
What I dont believe, and what I dont think there is evidence for is the simplistic calories in calories out interpretation of saying that the more you exercise, the more calories out and therefore you will lose weight. Thats nonsense. Because the body will compensate by making you hungrier. We have evolved a very complicated system over millions of years to preserve homeostasis.
It is certainly true that strong homeostatic mechanisms regulate weight gain in humans. Perhaps strengthening this homeostasis through exercise provides much of its protection against weight gain. However, it is also true that this homeostatic system evolved under conditions where humans were much more physically active than modern humans. All homeostatic systems have limits and it is plausible that at very low levels of physical activity the homeostatic system does not work so well. If this is the case, increases in physical activity from very low levels to moderate levels could have some positive effect. But, this is speculation.

Although the World Cancer Research Fund study shows that physical activity is protective against weight gain, it does not delve deeply into the mechanisms behind the protective effect. They do cite some evidence suggesting that the increased insulin sensitivity from regular physical activity may play a role. So, you certainly could be right that the positive effects of exercise on weight maintenance are not primarily due to the increased energy expenditure due to physical activity. Certainly the Church study shows that compensatory effects do exist. Whether the simple calorie in/calorie out explanation or some other explanation mediates the protective effect of exercise is an a question that probably requires further study.

Have you read this article from Gary Taubes ? You dont seem the kind of person who dismisses folks without reading the evidence, so please do read it.
http://nymag.com/news/sports/38001/
There is other evidence too, let me try and dig it out. Wish I had more time.
I agree with the general point of the article: exercise alone will not help one lose weight. Controlling one's diet is another important factor and can often be more important than exercising. If the sole goal is weight loss, exercise may not be the most important factor (although I haven't seen any good evidence yet showing that it hurts weight loss as suggested by the article). Consistent with this view, the WCRF report cites many randomized controlled trials that show that a combination of physical activity and dietary interventions are effective at promoting weight loss.

Finally, the fact remains that strong scientific evidence demonstrates that exercise helps to maintain body weight and protects against weight gain as well as other diseases like diabetes, cancer, and heart disease. Even though regular physical activity may not promote weight loss as well as people think, there are still many good reasons to exercise regularly. Exercise may not necessarily make one thinner, but it will certainly make one healthier.
 
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Siv

Gold Member
84
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Very well written, Ygggdrasil.
While you and I may differ on some points, overall I think I agree with what you say.
 
Ok, read this news article yesterday.
http://www.dailymail.co.uk/health/article-1323758/Can-cutting-Carbohydrates-diet-make-live-longer.html?ito=feeds-newsxml
Can cutting carbohydrates from your diet make you live longer?
i certainly have doubts about much of it. we're certainly not worms or lab rats. very little of the stuff that works in rats re obesity pans out in humans, fwiw.

some things are fairly obvious. kids are eating a bit too much and not exercising as much now. this tends to accelerate some things physiologically, like puberty. it will be interesting to see how that pans out (after i'm dead and gone, most likely), but i'm guessing it shortens their lifespan. being obese is bad, there's not much controversy there.

the other side of the coin is to presumably increase lifespan by decreasing caloric intake, perhaps even below what used to be considered normal. you probably don't want to do this in children and adolescents, especially females. one obvious problem is that most women are prone to osteoporosis in old age, and by age 30, they've got all the calcium they will ever have in their bones. from there it is all downhill. both diet and exercise are important here, as exercise will provide hormonal stimulus to build stronger bones.

later in life, you run into other things. elderly people actually have a better life expectancy if there is a little bit of chub on them. and as always, being too obese will never help, but that typical J-shaped curve(if you're underweight, mortality goes up, overweight and mortality goes up) for longevity shifts to the right a bit.

in general, it seems that optimum BMI is neither too high, nor too low, and optimum may vary by life stage.

and there are other things. for one, we humans don't seem well-designed for conserving calories. we seem designed for keeping our big brains alive, generating copious amounts of heat. we also seem well-designed for traversing long distances on foot, wearing down lesser animals with not speed, but sheer persistance. both of these functions demand copious and efficient fat storage. and come with the expectation that there will be intermittent periods of starvation.


another idea i'd like to throw out there (and i think this is a fairly new topic of research, so there isn't a mountain of data yet) is the http://www.ncbi.nlm.nih.gov/pubmed/15836464" [Broken].
 
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2491496/?tool=pubmed

I love this mouse!! I read about it a few years back - but he shows some definite and drastic changes in phenotype in response to a single gene overexpression in a place where it usually ain't!!! Put a liver enzyme in skeletal muscle - change how the muscle is fuelled - and watch him go! It's pretty amazing.

As usual - its a mouse - so I aint saying anything about the human condition - but its very interesting nevertheless.
 
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Ok, read this news article yesterday.
http://www.dailymail.co.uk/health/article-1323758/Can-cutting-Carbohydrates-diet-make-live-longer.html?ito=feeds-newsxml
Can cutting carbohydrates from your diet make you live longer?
There is an obvious question that arises after reading this article.

Your body needs energy. This energy can come from carbs, fat or protein. Regardless of the source, the only way the energy can get to your internal organs is via blood glucose. Insulin is released by the pancreas in response to blood glucose. Even if your diet is 100% fat, that fat is converted into glucose via ketogenesis/gluconeogenesis before the energy can be used.

What reason is there to think that consuming 2000 calories/day of "slow release" complex carbs will result in significantly different levels of insulin from consuming the same 2000 calories/day of fat and protein?
 

Siv

Gold Member
84
5
There is an obvious question that arises after reading this article.

Your body needs energy. This energy can come from carbs, fat or protein. Regardless of the source, the only way the energy can get to your internal organs is via blood glucose. Insulin is released by the pancreas in response to blood glucose. Even if your diet is 100% fat, that fat is converted into glucose via ketogenesis/gluconeogenesis before the energy can be used.
I am no biochemistry expert (Dr. Stephan Guyenet is, BTW) but here's what it says from everyone's favourite source - wiki -
Most advocates of low-carbohydrate diets, such as the Atkins Diet, argue that the human body is adapted to function primarily in ketosis.[62][63] They argue that high insulin levels can cause many health problems, most significantly fat storage and weight gain. They argue that the purported dangers of ketosis are unsubstantiated (some of the arguments against ketosis result from confusion between ketosis and ketoacidosis which is a related and very dangerous condition).[64] They also argue that fat in the diet only contributes to heart disease in the presence of high insulin levels and that if the diet is instead adjusted to induce ketosis, fat and cholesterol in the diet are not a major concern (although most do not advocate unrestricted fat intake and do advocate avoiding trans fat).

On a high-carbohydrate diet, glucose is used by cells in the body for the energy needed for their basic functions, and about 2/3 of body cells require insulin in order to use glucose. Excessive amounts of blood glucose are thought to be a primary cause of the complications of diabetes; when glucose reacts with body proteins (resulting in glycosolated proteins) and change their behavior. Perhaps for this reason, the amount of glucose tightly maintained in the blood is quite low. Unless a meal is very low in starches and sugars, blood glucose will rise for a period of an hour or two after a meal. When this occurs, beta cells in the pancreas release insulin to cause uptake of glucose into cells. In liver and muscle cells, more glucose is taken in than is needed and stored as glycogen (once called 'animal starch').[65] Diets with a high starch/sugar content, therefore, cause release of more insulin and so more cell absorption. In diabetics, glucose levels vary in time with meals and vary a little more as a result of high carbohydrate content meals. In non-diabetics, blood sugar levels are restored to normal levels within an hour or two, regardless of the content of a meal.

It is worth noting that while there are Essential Fatty Acids(EFA) and Essential Amino Acids(EAA) there are no essential carbohydrates of any sort and while a diet devoid of EFA or EAA will result in eventual death, a diet completely without carbohydrates can be maintained indefinitely without health detriment.
What reason is there to think that consuming 2000 calories/day of "slow release" complex carbs will result in significantly different levels of insulin from consuming the same 2000 calories/day of fat and protein?
I guess no other reason than the fact that it does. Have you measured your insulin and blood glucose levels after a mostly fatty meal ? People have. My mom has (she is a diabetic). If you add carbs, the difference is marked.
 
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I am no biochemistry expert (Dr. Stephan Guyenet is, BTW) but here's what it says from everyone's favourite source - wiki -
On a high-carbohydrate diet, glucose is used by cells in the body for the energy needed for their basic functions, and about 2/3 of body cells require insulin in order to use glucose. Excessive amounts of blood glucose are thought to be a primary cause of the complications of diabetes; when glucose reacts with body proteins (resulting in glycosolated proteins) and change their behavior. Perhaps for this reason, the amount of glucose tightly maintained in the blood is quite low. Unless a meal is very low in starches and sugars, blood glucose will rise for a period of an hour or two after a meal. When this occurs, beta cells in the pancreas release insulin to cause uptake of glucose into cells. In liver and muscle cells, more glucose is taken in than is needed and stored as glycogen (once called 'animal starch').[65] Diets with a high starch/sugar content, therefore, cause release of more insulin and so more cell absorption. In diabetics, glucose levels vary in time with meals and vary a little more as a result of high carbohydrate content meals. In non-diabetics, blood sugar levels are restored to normal levels within an hour or two, regardless of the content of a meal.
while i agree with this , it should be kept in mind this is normal mechanism in the body. People have tendency to eat excess carbohydrates mostly refined carbs, the body is given a new challenge to tackle this excess carbs. The normal mechanism is to secrete insulin which makes the cells in the body to take up the glucose and rest to store in liver as glycogen. what happens when we constantly take this excess carbs in the diet along with a sedentary lifestyle, is why the body has to adjust and undergo physiological changes like conversion of excess carbs into fat stored in body. The excess carbs also leads to increased insulin secretion which becomes limited or exhausted in the sense that it cannot be produced more after it reaches a certain level.

What reason is there to think that consuming 2000 calories/day of "slow release" complex carbs will result in significantly different levels of insulin from consuming the same 2000 calories/day of fat and protein?
I would like to see studies where calories got from fat and protein is better than calories from slow release complex carbohydrates, otherwise it only becomes an assumption.
 
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It is worth noting that while there are Essential Fatty Acids(EFA) and Essential Amino Acids(EAA) there are no essential carbohydrates of any sort and while a diet devoid of EFA or EAA will result in eventual death, a diet completely without carbohydrates can be maintained indefinitely without health detriment.
There are various types of fats and all are not essential for our body except linoleic acid,omega 3 fatty acids.

http://en.wikipedia.org/wiki/Essential_fatty_acid" [Broken]


No nobody is going to die if they don't eat carbs, carbohydrates are the easiest and most usable fuel in the body.

Proteins and fat are essential , but they are not easily used in the body - that is why the term ketosis usually arises whenever atkin's type of diet is suggested.

Most advocates of low-carbohydrate diets, such as the Atkins Diet, argue that the human body is adapted to function primarily in ketosis.[62][63] They argue that high insulin levels can cause many health problems, most significantly fat storage and weight gain. They argue that the purported dangers of ketosis are unsubstantiated (some of the arguments against ketosis result from confusion between ketosis and ketoacidosis which is a related and very dangerous condition).[64] They also argue that fat in the diet only contributes to heart disease in the presence of high insulin levels and that if the diet is instead adjusted to induce ketosis, fat and cholesterol in the diet are not a major concern (although most do not advocate unrestricted fat intake and do advocate avoiding trans fat).
what are long term effects of high protein and fat diet ? These studies are limited. Yes, better outcomes are seen, as some studies have indicated with regards to low carb diet.
Also there is a tendency to avoid foods such as vegetables and fruits even though they contain nutrients and fiber because they have carbs.

Not all fats are good. Trans fats are bad. Even proteins, high amount of red meat intake is associated with heart diseases , cancers .

http://en.wikipedia.org/wiki/Red_meat" [Broken]
 
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I guess no other reason than the fact that it does. Have you measured your insulin and blood glucose levels after a mostly fatty meal ? People have. My mom has (she is a diabetic). If you add carbs, the difference is marked.
I found this article

http://www.ajcn.org/cgi/content/abstract/66/5/1264?maxtoshow=&hits=10&RESULTFORMAT=&author1=holt&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT

Things are not as simple as one might think. Beef produces higher insulin response per calorie than pasta, and white bread produces more response than apples... And I bet there are some nonlinear effects too, e.g. eating twice the amount of food more than doubles the insulin response in the short term (though what happens to the integrated response, no one knows).

And I'm 99% sure that your mom has not measured her insulin levels after different kinds of meals. Glucose yes, insulin no. There are simply no commercially available blood insulin level meters on the market.
 
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The success rate of diet pills is very low and they seem to be a perfect recipe for self destruction as they can apparently cause heart attacks, strokes and numerous other major health problems.

When you peruse the link below you will be absolutely astounded (as I was) and you will probably wonder why diet pills were not banned a long time ago.
 

Siv

Gold Member
84
5
I would like to see studies where calories got from fat and protein is better than calories from slow release complex carbohydrates, otherwise it only becomes an assumption.
Studies? You have a whole big fat book, called Good Calories, Bad Calories. And its a very dry read, because it has pages and pages and pages of data and studies, plus of course tons of references.

And thats not the only book, there are many others.
 

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