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Medical Low Fat Diets Make You Fat?

  1. Aug 15, 2008 #1


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    I've wondered about this.
    It would be my observation that the advent of the low fat/cholesterol diet is the one major factor that occurred coincident with the population weight gain.
    The fear/safety phenomena is another possibility, but I would tend to limit this more to the current generation of children.
    TV watching and Fast Food existed for quite some time previously.

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  3. Aug 15, 2008 #2

    jim mcnamara

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    IMO - No. You can lose weight in any of those diet regimens. How much weight loss is affected - not that low-fat makes you fat(ter).

    What they are talking about is overall results in a small-ish population of 'dieters', who stuck to a diet regimen for 24 months. Everybody lost weight, but the low-carb dieters lost the most. And had the largest reduction in blood cholesterol levels. I am assuming the results are statistically significant, but I can't get to the original paper, so I'm guessing. Someone please correct me if I got it wrong. I do not think it correlates with the current zeitgiest.

    IMO - what really counts is where the same population of folks are weight-wise in five years.
    Last edited: Aug 15, 2008
  4. Aug 15, 2008 #3


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    I suppose my concern boils down to this.
    These were all calorie controlled diets with supposedly balanced nutrient intakes.
    Vegans seem to be fairly aware of of the difficulty in balancing nutrient intake and put quite a bit of effort into getting the right mixture of food stuff.
    I doubt this is true of the general population.
    I'm inclined to think that people will over eat the so called low-fat items touted in the stores to obtain elements that are in short supply in these items that are plentiful in the so called bad sources.
  5. Aug 15, 2008 #4

    jim mcnamara

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    This discusses populations at risk with respect to vitamin b12. Vegans included.
    Which is what I guess you are talking about, since you mentioned vegans, and they are a population at risk for B12, and protein deficiency problems. Most of do indeed seem to be aware of this.

    So, then, aside from the super-diet-conscious types, who probably do not need to be on low calorie diets anyway, your hypothesis is:
    "populations on lowfat diets tend to eat more calories in search of nutrient [X]"

    Could you fill in the [X], please?
  6. Aug 16, 2008 #5
    Well...there are still tons of people who eat high-fat fast food. None of those companies you mentioned are going out of business anytime soon...
    ...however, the trend toward healthier eating has forced fast-food companies to accomodate these customers. McDonalds has rolled out premium salads. Wendys allows people to substitute side salads or a baked potato instead of french fries in value meals.
    Sales aren't down by all that much. People still jam the drive-thrus at lunch hour. But now, the healthier eaters at least have an option or two...the lesser of the evils.
    these diets were popular 15 years ago (or more) & people did lose weight as it was more often combined with a high fibre diet-so you ate low fat & high fibre. It was something like 25gms fat a day & 30+ of fibre...and that is a lot of fibre to get through!
    No matter how they phrase it, its still just reducing calories overall- its the total amount in that puts on the weight, not where they come from.
    Last edited by a moderator: Aug 16, 2008
  7. Aug 16, 2008 #6


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    Some people often confuse foods that are labeled as "low fat" to mean "low calorie". They will eat a one pound bag of "low fat" cookies thinking that they aren't going to gain weight if they keep their daily intake of fat low.

    It's a lack of education.
  8. Aug 16, 2008 #7


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    If I could do that, I'd write a paper on it :smile:
    However, fat is a fairly balanced protein source.
    If all you do is substitute "fat free" products into your diet I suspect you could easily develop an unbalanced protein intake.
    I might think that people would overeat to make up the missing required ingredients.
    Is there anything to this?

    The study I posted a link to suggests that the common perception of "healthful" low cholesterol diet seems to be somewhat suspect as the better cholesterol response occurred with the counter intuitive diet.
    What actual support is there that reducing fat in your food intake reduces cholesterol?
    Particularly for people without an actual genetic complication.
    I don't think I have ever come across anything concrete in this line.
    Calorie restriction itself should probably lower cholesterol by itself.

    From a purely qualitative perspective.
    I notice that the people I know who are the most into the common perception of a low cholesterol diet have become the most overweight.
    Is it cause or effect here?

    I was part of one of the original cholesterol baseline studies.
    So I had some idea of my cholesterol level, and what it meant, even though it was probably another 10 or 15 years before a general cholesterol test became available.
    I never changed my overall diet and think that low fat products taste simply awful.
    While people keep telling me that my diet will kill me, testing indicates my levels are just fine being around 112 LDL and 185 total. The Doc says my weight is excellent.
  9. Sep 7, 2008 #8
    No. Although many protein sources contain fat, fat is not a protein source and cannot be in the human physiology. Here is why:

    Fatty acids are similar to long hydrocarbon molecules with a carboxyl (COOH) group at one end. The molecule can either be saturated with hydrogen or have missing hydrogen pairs (which makes it unsaturated). The fatty acids are often transported and stored in groups of 3 tied to a glycerol group (triglyceride). Fatty acids and triglycerides do not contain any nitrogen.

    Proteins are made up of amino acids (9 of which are essential). In turn, an amino acid consists of an amino (NH2) group at one end, a carboxyl group at the other, and a side chain in between. The side chain determines the identity of the amino acid and some of these side chains (such as that for Methionine) contain sulphur.

    With the abscence of nitrogen and sulphur, fats cannot supply amino acids.

    The blaming of low fat food for obesity is really not accurate. As the law of conservation of energy and the second law of thermodynamics would have it, the only way to become obese is to intake and excess of empty calories and to do so over a long period. Besides, many of these studies are based on surveys. The problem here is that there is often a disparity between what people eat and what they say that they eat. I have many times sat across the table from people who brag about their healthy eating habits between bites of greasy disgusting junk that I wouldn't touch.
  10. Sep 7, 2008 #9
    I've read that obesity is primarily caused by lack of sleep and lack of exercise and not by consuming a lot of calories for too long.

    Suppose that someone eats 2500 kcal per day and has a constant body weight. If that person were to eat 100 Kcal per day less and keeps his activities exactly the same, then will he continue to lose weight and starve to death? Of course not! His metabolic rate will simply adjust to his new diet. He'll only lose some fixed amount of weight, there is no long term downward trend in his weight. The same is true if he were to eat 100 Kcal per day more. He'll gain a bit of weight, but then the weight should stabilize.

    Without such feedback mechanisms regulating the metabolic rate, animals in the wild would not last long. I've read that lack of sleep and lack of exercise cause weight problems, presumably because they interfere with the body's ability to regulate the weight.

    It is not understood exactly how this works. But it seems logical to assume that the body makes the metabolic rate during sleep dependent on the energy intake. Changing the metabolic rate during sleep has less impact on your daytime functioning.

    Now, if you don't sleep enough, this fine tuning mechanism won't work well and your weight would tend to fluctuate. But, since it would be a bad idea for a biological system to allow for large downward fluctuations of the weight, lack of sleep should trigger your overall metabolic rate to go down a bit so that the system will be biased in favor of weight gain.
  11. Sep 8, 2008 #10

    Andy Resnick

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    I concur. Empty calories are still calories.
  12. Sep 11, 2008 #11
    There are 2 main reasons for this:

    1. Calorie reduction by itself (without exercise) usually involve some muscle loss. This will lower the Basal Metabolic Rate and thus the caloric expenditure.

    2. A lighter body will need less energy (Calories) to move around.

    I am forced to doubt the accuracy of the source that you read for this reason:

    Anything that converts energy from one form to another can always waste energy however, nothing (including animals) can pull energy (Calories) out of nowhere. This is why it takes a 3500 Calorie deficit to lose a lb of fat and why it takes over 4000 Calorie surplus to gain a lb of fat (~9 Cal/gram). This is due to the Second Law of Thermodynamics. In short, biology has to obey the laws of physics. Here is an analogy to think about:

    If a car started a journey with half a tank of gasoline and returned with a full tank, did the laws of physics yield or did someone add gasoline to it?
  13. Sep 11, 2008 #12

    I agree, but you have to take into account that we are warm blooded animals. We waste energy all the time. So, it is better to compare the human body with a car whose engine is always running. Let's assume that at night it is running idle and at daytime you want to be able to be unconstrained as much as possible.

    Then, you can use the time when the car is not used to burn off eexcess fuel by letting the engine run a bit faster. Or, if you've used a bit more fuel than usual, you can let the engine run a bit slower at night. So, as long as you stay within some reasonable bandwith of fuel use during daytime and fuel tanked, you can make sure that each morning when you start to drive your car again the fuel you have in your tank is exactly the same.

    Now, the shorter you make the "resting period" the more difficult it becomes to fine tune the fuel weight. Now, if you are not careful with the fuel management, you can get an empty tank simply because you use a small amount of fuel more than you take in. So, to avoid that you need to be extra careful and keep a larger fuel reserve.

    Back to biology. If you are a lion then staying fit and being able to maintain the same level of fitness is important. You don't want to lose weight just because you've been eating a little less for a few months. If you eat a lot less then that's a different matter. But keeping your physical state the same as much as possible surely is an advantage.
  14. Sep 12, 2008 #13


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    I don't have any problem with what you say about fatty acids, although some are required dietary items because your body can not make them.

    Not quite what I had in mind when I said fat though.
    It would be my understanding that something like milk fat isn't just fatty acids, but a fairly complex mixture of proteins with a lipid core.
    For instance to get your no fat milk the entire complex is centrifuged out.

    So the cholesterol conscious people drink no-fat milk (whatever is left over) or substitute soy milk (vegetable proteins in water)
    This goes back to my previous comment about the vegan diet where it's fairly well known that certain combinations of things must be eaten together to obtain a balanced input.
    Eating them on separate occasions is not the same.

    So my question is more of what kind of deficiencies are being introduced into the average practitioners diet?
    How much do people over eat to obtain what are now trace elements in their diets?
  15. Sep 13, 2008 #14
    Valid points. It seems that our disagreement is more due to miscommunication than to a lack of understanding of the science. It seems that you are talking about what happens when someone is at low fat percentages. I was talking about how someone would go from a normal fat percentage to being obese.

    I agree with much of your last post except this part. Actually, http://www.nutritiondata.com/facts/dairy-and-egg-products/139/2" [Broken]. However, you do not need to take my word for it. The next time that you are in a supermarket, you can look at the labels in the dairy section and see for yourself.
    Last edited by a moderator: May 3, 2017
  16. Sep 15, 2008 #15


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    The weight weight of solids to water doesn't have anything to do with this.
    Neither does the quality, or lack thereof, of the specific proteins.
    After all, at least some denaturization most likely occurs during the pasteurization process.
    Or the same for cooking/storage of any food.
    This question doesn't have anything to do with milk other that being a common example of the changes occurring with the no-fat diet.
    It seems that after whole milk is turned into skim milk it now consists primarily of two proteins kappa-casein and Lactoglobulin, a large reduction from the original protein content variety.

    I'm just curious on the impact this might have taken across the board when people change their diet to consist of primarily "no-fat" food.
    The link I posted originally implies there might be.
    I'm just curious as to if there is any additional information along this line.
    Last edited by a moderator: May 3, 2017
  17. Sep 16, 2008 #16
    First, I think that we can both agree that the role of essential fatty acids in numerous bodily functions renders a fat free diet (or any other nutrient deprivation diet) to be unhealthy. That is why they are nutrients.

    However, the quality of the protein has everything to do with its nutritional value and here is why:

    1. Ingested proteins are broken down into their individual amino acids before they are transported via the portal vein into the liver where they are re-constructed into proteins based on the body’s needs. Proteins that enter the bloodstream intact can potentially trigger the body’s defenses resulting in allergic reactions.

    2. If there is a shortage of any essential amino acid or essential combination of amino acids (i.e. Phenylalanine/Tyrosine combination), much of the amino acids will be deaminated and used for energy (calories) instead of protein synthesis. A high quality (complete) protein has at least 100% of the required concentration (mg amino acid/g of protein) of all of the essential amino acids and required combinations. The World Health Organization and the Institute of Medicine have some very useful literature on this.

    Incidentally, casein and lactoglobulin (whey protein) have the required amino acid profiles to be considered complete proteins. However, throwing in a bunch of other proteins in the mix could potentially lower the concentration of the essential amino acids per gram of protein if the other proteins are deficient in the essential amino acids. I believe that this mixture (in whole milk) is ideal for bovine physiology but not necessarily so for human physiology. Human milk however, is a different story.

    Here is some literature that I think that you might find to be useful:

    http://whqlibdoc.who.int/trs/WHO_TRS_935_eng.pdf" [Broken]

    http://jn.nutrition.org/cgi/reprint/133/9/2953S" [Broken]


    Also, I read your link again. I do not believe that the experiment was well conducted because they could not monitor what or how much the people actually ate.
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  18. Sep 18, 2008 #17


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    This statement might qualify as an answer to my question, depending on the degree that it applies to the specific situation.

    Since the topic was brought up in one of the links, I noted some concerns related to the digestibility of unmodified whey proteins. This would seem to make the application of the term high quality somewhat suspect in this case. No idea as to if this applies to the casein component.

    Unfortunately, this problem seems to apply to all dietary studies I've seen, not that I'm claiming any extensive knowledge of the literature, so it my observation might simply reflect my level of ignorance on the topic.

    PS: Thanks for the links.
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