How and when would you die on a zero-fat diet?

[magic9mushroo]

TL;DR Summary

"What-if" question.

I know that linoleic acid and alpha-linolenic acid are essential fatty acids for human life. What I don't know is when, exactly, you'd die from not having them, and precisely what would give out.

So, assuming a healthy person suddenly switched to a diet with zero fat (I know this isn't actually possible with natural foods, because of cell membranes, but assume it's all processed or whatever) that still had enough of everything else, how long would it take them to die and what would they die from (if it's organ failure, which organs, and if it's something else, what would it be)?

-m9m

 

[FactChecker]

It is called "rabbit starvation", or "protein poisoning". One famous death due to it was Chris McCandless. It certainly is possible while still eating plenty of natural foods if they are too lean.

 

[Laroxe]

Yes, I think the major problem is in the fat we need fats to absorb a number of micronutrients like Vitamin D for example. Not eating fats would also have an impact on our catabolic metabolism, we would need to produce many of the fats we use in our bodies by using other energy resources and some fats can't be produced.

This can have a wide range of health effects for example it reduces the effectiveness of some of our natural barriers like the skin, making us more prone to infection. Our ability to maintain tissue structure and repair is impaired our energy reserves are reduced etc etc. Its impossible to give any sort of estimate as to survival, death would tend to be a protracted affair unless we developed a serious infection and the problems tend to accumulate over time.

 

[Mark44]

It is called "rabbit starvation", or "protein poisoning". One famous death due to it was Chris McCandless. It certainly is possible while still eating plenty of natural foods if they are too lean.

"Rabbit starvation" is one theory. I remember reading an article in the newspaper back around the time that McCandless's death occurred, as well as the movie ("Into the Wild") based on the book of the same name by Jon Krakauer. In the movie it was postulated that he had misidentified some berries that turned out to be toxic.
The Wiki article in the link above contains some new information, and theorizes that McCandless's death was caused by eating a kind of wild potato that contains a toxic amino acid, that caused paralysis in his legs. The earlier thinking was that the berries McCandless was eating contained a toxic alkaloid, but no such alkaloid was found by those researching his death.

Regarding "rabbit starvation" I seem to remember reading a long time ago about Arctic explorers whose diet consisted mainly of rabbits that they had trapped. The rabbits contained so little fat that some or many of those explorers died of starvation. It was many years ago that I read about this, so can't provide any references.

 

[BWV]

By your own hand after about 6 months ;)

 

[BWV]

Seriously, I think most of the premodern peasant population of Asia ate very little to no fat - subsisting on rice and vegetables

Similarly 16-17th century European peasants were unable to afford fats or meats and predominately ate gruels

 

[jim mcnamara]

@BWV
Cereal grains straight off the plant contain fat. Ever hear of rice bran oil for example? It is derived from rice bran (the brown color on brown rice). Most rice is stored as white rice because the fatty acids in brown rice lead to rancidity during storage.
https://en.wikipedia.org/wiki/Rice_bran_oil

Olive oil also come to mind.

Flax seed oil (linseed oil) contains ~50% alpha linolenic acid - an omega-3 fatty acid that human biochemistry converts to DHA Docosahexanoic acid and EPA Eicosapentanoic acid. Both are required fatty acids. The shared biochemical cascade that synthesizes them "fights" over a precursor molecule such that it only produces ~15% DHA.

Walnuts and other tree seeds have unsaturated fatty acids, too. Walnuts are 65% lipids.
https://fdc.nal.usda.gov/fdc-app.html#/food-details/1100553/nutrients

Before the folks interested in this thread go too far off into speculation please consider using the standard reference for what nutrients are in a food item. Most countries have one, a good one is:
https://fdc.nal.usda.gov/ - the one I used above.

FWIW the people living in Europe during the middle ages had children, right?

When diets go low enough in fat, women do not have menses - ammenorrhea. No ovulation == no kids. This is so uncommon, today in first world countries, that physicians almost always look for other causes.

Usually: (To my knowledge it is ) largely associated with anorexia nervosa patients.
Vegans learn about this problem. Then they take pills derived from marine algae, or use flax-seed oil in cooking and as a supplement.

Periodic famines in Africa do result in this condition.

 

[jim mcnamara]

To answer the original question - there is nothing useful I can find in the literature.
Since lipoproteins (lipo==fat) are an intrinsic aspect of nutrient absorption in the digestive tract I would guess that when you run out of stored fat you can no longer create lipoproteins in the liver.

Using that assumption, plus sufficient carbohydrate & fat-free complete protein calories, time required to use up stored required lipids would be be a primary driver.
Lipogenesis (making fat from excess carbohydrates) would probably extend that period, but it cannot make all required lipids. Cell division goes on constantly in the gut. New cell membranes require fatty acids.

My guess is: absolutely do not try this yourself to find out.

Literature searches mostly turn up case studies on ketogenic diets like the 'Atkins Diet'. They allow fats. Some studies show increased mortality others do not. This is often what nutrition research shows due to uncontrolled confounders. You cannot do completely controlled experiments on people like you do with mice. So we are kind of stuck.

 

[Rive]

Similarly 16-17th century European peasants were unable to afford fats or meats and predominately ate gruels

I don't know enough about the Asian population, but the usual low-class diet of that time is frequently underestimated. To start with, some (oily) seeds were often part of the daily diet. Especially, since they could be easily preserved. Also, that time foraging was always part of any low class diet (although hunting was usually not permitted, but that meant only some specific species and areas).
Bigger animals meant wealth, but small animals kept in the backyard (don't know the specific term valid for that time) were simply not noted and were common.

To answer the original question - there is nothing useful I can find in the literature.

As your previous comment about fat/oil content in plant products kind of indicated, it is actually rather hard to create and maintain a diet which still has sufficient vitamins but so low fat/oil content that the latter would be the faster to kick in...

 

[Laroxe]

I was thinking about this and like most people couldn't really find much in the literature that made much sense. It made me think about how difficult it can be to make much sense anyway of the way in which the environment, different sorts of intake, the physiological effects of that intake, age, individual predispositions and individual needs, all interact over time. It may be why research on nutrition and health is so problematic.

A few of the issues to consider is that nutritional needs differ, individuals that live in very cold climates and engage in high levels of activity require a diet that provides high calorie foods. Interestingly, populations from such areas have traditionally eaten diets high in Protein and fats while relatively low in carbohydrates, both proteins and fats have physiological limitations on their use for energy. The by-products of their metabolism, principally by the liver, lead to increased levels of ketones and urea, both of which have the potential to be toxic. One of the observations in Inuit populations who eat traditional diets is that they have enlarged livers and a high level of diuresis, these are likely to be adaptations that develop over time, that an explorer would not have. We also know of adaptations towards foods that are heritable in populations, lactose tolerance being an example, this can also change with age.

The current fashionable narrative of meat being bad, rather misses the point that meat is what we are made of, while cooking improved the bioavailability of the main nutrients, eaten raw, meat provides significant amounts of virtually all the micronutrients we need. Plants on the other hand, being unable to run away, have over time developed ways to protect themselves and their nutrient sources. Over time, they have become expert in chemical warfare and the use of passive defences to prevent their digestion, in fact the range and complexity of their defences is perhaps the main reason that the liver is such a large organ generally. The common effects of nausea and diarrhoea can lead to dehydration, which can be deadly to those in a toxic state. Few of the plants we typically eat are now recognisable in nature, we have bred the worst traits out of them and others can require complex processing. Others actually contain compounds that prevent the absorption of nutrients, which may only cause problems for those already on a restricted diet.
Trying to pin down the causes of malnutrition in people living in the wild and on restricted diets becomes really difficult, as all the significant changes can become stressors that affect their other coping resources. A person experiencing ketosis and other metabolic stressors may have difficulty processing other issues like low grade dietary toxins.

It seems that there is little evidence to support the view that the restriction of fat in the diet is a likely cause of the reported deaths and in the case of McCandless, there are likely to be many more likely causes.

This is interesting;

https://www.discovermagazine.com/health/the-inuit-paradox