Saturday 28 May 2011

Is obesity bias evolutionary?

On the Huffington Post and on his own blog, David Katz, MD, asks the important question why so many people are obese nowadays. His answer does not sound convincing, he argues that there a bias toward obesity is an evolutionary advantage.

This might have been possible, but a simple calculation shows that this is unlikely. A man who is 100 kg too heavy and 50 years old, to a first approximation ate 2 kg per year too much. Two kilograms of fat is 1400 Cal and thus comparable to what one eats in 4 days to one week, depending on your, height, weight and level of activity. In other words, this man ate only about one or two percent more than he should have. You may increase this number somewhat to account for the fact that a larger body also needs more energy. Still the additional amount eaten by an overweight person is small and will be hardly noticeable in day life.

In the times that humans were hunters and gatherers, it should have been easily possible to eat a few percent more than usual. The year to year variability in the availability of resources is large; on the negative side think for instance of floods, droughts and grasshopper plagues. A human that is able to survive in a bad year, should easily be able to hunt or gather double his need in good years. One would expect the maximum amount of food a person can find is much more than a few percent more than the average needed. Otherwise, a human with a bit of bad luck would soon starve to death and be removed from the gene pool.

This may be illustrated by numbers from other animals. Ecotravel states about lions that: “If suitable prey is available, lions eat every 3 to 4 days, but can go without food for more than a week. They average about 5 to 7 kg meat daily, but can consume about 25% of their body mass if necessary. An adult lion will kill in the region of 15 animals per year.” Such a lion has some spare time to hunt more often. The same was most likely also the case with early man.

Not only should it be very easy to eat more than a few percent more than you need, then and now. It should be very difficult to estimate within a few percent how much food is needed and how much energy is in the food eaten. Thus, there is bound to be a feedback mechanism that keeps the energy stores not too low (starvation, reserve for bad luck and illness), but also not too high (slows one down, more attractive prey). As I have illustrated above, this feedback mechanism was always already needed. This feedback would use information on how much energy is stored in the body, similar to a thermostat using the room temperature and not an estimate of how much the heating warms and is lost through the windows and walls.

Thus looking for a cause of obesity, we should have a look what we do differently now that may break such a feedback mechanism. The most straight forward change is that we are continuously eating carbohydrates (bread, pasta, potatoes, etc.). As the stores for carbohydrates (glycogen) are small, carbohydrates are used first for fuel. Someone who eats carbohydrates day in and day out does not use his fat burning capabilities. Just as with muscle, bones and your brain, the saying “use it or lose it” is likely also true for the metabolic system for fat. Enzymes for fat burning that are not used, are produced less, just as any other enzyme. If the enzymes are missing, the body no longer notices the large fat stores; these stores no longer provide sufficient energy when needed.

Another obvious change is that we are less active, which together with eating carbohydrates, means that the glycogen stores are often full to the brim. This may lead to problems with blood sugar at the next carbohydrate-rich meal or snack. The blog Marks daily apple has much more background information on the difference between then and now and how we can mimic past behaviour to achieve better health.

Further reading

More posts on paleo (diet and lifestyle topics inspired by evolutionary thinking).

Paleo and fruitarian lifestyles have a lot in common
A comparison of the main ideas and recommendations of these two lifestyles.
Natural cures for asthma?
Some ideas for natural ways, which helped me cure or reduce asthma.
Sleep and diversity
Differences in sleeping times, from early bird to night owls, may provide security advantages.
Freedom to learn
Forcing children to learn stifles their innate motivation to teach themselves and may thus be counter productive.
The paleo culture
After the Ancestral Health Symposium 2012, as discussion started about the sometimes self-centred culture of the paleo community


  1. I don't agree that diets rich in carbohydrates cause obesity. After all, this is my diet and I'm not obese :)

    Ok, so a case study of just one is not very much but I think it comes down to physical inactivity and over-eating. I actually think it's very hard to put on weight as a vegan. I don't even think there is such a thing as an obese vegan?

  2. That was the unimportant detail of the post. :-)

    Everyone is different. May I assume from how you look that you have never been overweight?

    I also eat a decent amount of carbohydrates nowadays. When I wrote this post, I experimented with eating less carbs and once in a while I skipped a meal or even fasted for a day. Since that time I am no longer hungry so easily and so quickly after eating. It is a small experiment (just one person), but I feel that was due to the fasting, which was easier because I already had some "training" of my fat metabolism due to eating less carbs. Skipping a meal is still easy for me, also now that I again eat more carbs.

    Not being hungry is quality of live in itself and is likely also a reason that I have become much more healthy. When you are hungry you body likely only allocates energy to the most necessary processes. For example, my skin is no longer dry, asthma and hay fever are gone, digestion is mostly perfect and quiet. I did gained weight the last year, which is not good as I already was too heavy, but even if that is a long term effect of the diet, I would say the health gains are worth it for me.

    Vegans may be thin, but they often do not look healthy. Dry skin, quick ageing. This may be because they do not implement it well.

    While there are vegetarian cultures and I would expect you can be healthy on a traditional vegetarian diet, a vegan diet is a new experiment and some vegans get huge health problems and often do not think of their diet because initially they noticed improvements. Many of the people in the paleo community were veg*n for health reasons before and report on enormous improvements in their health. Similar to the initial improvements as veg*ns report when they switch from a standard industrial diet to a veg*n diet.

  3. :-) My own comment went into my mail spam folder. Diet is the topic of much spam.

  4. Vegans don't age quickly. Where did you hear that? And why is it that when a meat-eater is sick no-one ever says, "That's because he eats too much meat". Whereas when a vegan gets sick it's immediately blamed on their diet.

    My sister is 3 years older than me and eats meat yet I think she looks much older than just 3 years. I don't think I look unhealthy or have aged quickly.

    This woman looks pretty good too:

    And have you seen the 78 year old vegan body builder:

    How do I get notification of replies to comments. There used to a box I could tick but that isn't an option anymore.

  5. :) Shall I advertise smoking by showing two smokers who lived long? The guy looks impressive, the woman wears make-up, (how can one judge how good her skin still is?) she bleached or photo-shopped her teeth (they are unnaturally whiter than her eyes), something many vegans have trouble with. But everyone is different, most vegan ate a complete diet when they were young and many of the nutrients they no longer get at stored in fat and last a long time, especially if you are lucky and do not need much.

    The woman that "looks pretty good" put a recommendation by Campbell on her homepage. He is the author of The China Study. He finds some correlations between meat eating and Western decease in China, never even considers that meat and Westerns lifestyles are both related to wealth and thus highly correlated. Consequently he never showed that the relationship is not simply due to Western lifestyles. In the second part of his book he puts rats on a diet high in one kind of amino acid, gives them a cancer initiator and finds they get cancer. That is comparable to putting humans on a 50% sugar diet, giving them a cancer initiator and claim that carbs are bad for you.

    When I lived in The Netherlands I knew quite a number of vegans. Some of them looked much too old for their age, especially their skin and hair had aged fast, which is a sign of intestinal problems as well (that is also skin). These were typically people who did not value their health that much, they just left out animal products without replacing them.

    I felt pretty bad after almost a decade of being vegetarian. Might not have been the reason, but I do not feel like another experiment, and certainly not like a more extreme vegan experiment. I know someone who eats mainly fruits for several years, looks healthy, is friendly and strong like an ox; everyone is different. I have no difficulty accepting that you feel good on such a diet.

  6. I think you can only get email follow-up if you have a Google account and sign in first. Stupid and one more reason to change to Wordpress. Then there is a checkbox "Email follow-up comments to ..."

  7. ":) Shall I advertise smoking by showing two smokers who lived long?"

    Yes, I realise that's not a very good argument but you did the same thing! So there :)

    In any case, I'm not trying to argue that vegan diets are best. Obviously it's a personal choice. But there's lots of evidence to support eating a plant-based diet especially for longevity. Here's a good article:

    "The FHILL longitudinal study shows that a higher legume intake is the most protective dietary predictor of survival amongst the elderly, regardless of their ethnicity. "

    If I was going to describe the perfect diet I think it would be a diet that contains lots of different species of food, lots of fresh foods, and lots of wholefoods (no processed foods). I also think a predominantly plant-based diet is best with meat consumption limited to once or twice a month and little or no dairy products.

    I couldn't find anything in the literature about faster aging and vegan diets. However there's quite a lot of evidence to support plant-based diets with low meat consumption -

    "In summary, greater adherence to the Mediterranean diet was significantly associated with longer leukocyte telomere length, a marker of biological aging. Our results further support the health benefits of adherence to the Mediterranean diet."

  8. Touché. :)

    Sounds like a good diet. I do not think we need much meat (although I also do not think it would be unhealthy as long as you eat the entire animal and not just muscle meat). The main health problem is probably eating much processes foods.

    I wish the rules of ecological animal husbandry were more strict. That the animals have a good life is important to me. Both morally, but probably also healthwise.

    And I always thought that when a meat eater dies, people blame it on their diet. Different cultures.

  9. I thought I left a comment about teeth but I can't see it. Maybe it's in your spam folder?

    In any case, I just wanted to say that I had a look in the literature and I can't see anything to suggest that vegan diets are bad for teeth. I've certainly never experienced anything personally and I would never spend money of cosmetic things like teeth whitening. My daughter has cavities but she is not a vegan and eats quite a bit of meat at school.

    I think the risk factors for teeth are not flossing and brushing regularly, consuming sugary drinks and foods, and smoking.

  10. I do not see an earlier teeth comment. Sorry.

    We are the only animal that needs daily flossing and brushing. For me that is a sign that there is something wrong with our lifestyles nowadays. Strong teeth and immune system are probably also important.

    Since I changed my diet, my teeth have also become much cleaner. They were often still sticky after brushing very long. At the end of my vegetarian period, I suddenly had a lot to cavities, but maybe also just because my new dentist liked the money. No new ones since I changed dentists. Now I sometimes almost wonder whether I still need to brush, but it is routine and a small job, thus I prefer not to make the experiment.

    Interesting that the literature does not show much evidence. Denise Minger writes a lot about teeth problems for vegans, she had them herself. If you are diligent you can probably avoid them. It is also a bit topic for the Weston A. Price Foundation. A more female group than the paleos that are interested in traditional diets rather than "stone age" diets.

  11. "We are the only animal that needs daily flossing and brushing. For me that is a sign that there is something wrong with our lifestyles nowadays."

    I don't think this is correct. Other animals would have better teeth if they brushed and flossed them as well. I have heard that sometimes wild carnivores end up dying of starvation because their teeth have fallen out and they can no longer eat their prey. I also used to be a dog owner and dogs need to have their teeth brushed regularly as well. Ask any veterinarian. If you don't brush their teeth they get cavities and gingivitis just as humans do. I think zoo keepers also have to care for the teeth of animals in zoos.

    I'd prefer to see some real evidence for vegan diets being bad for teeth rather than just someone's - who is not a dentist - blog :) My uncle is a dentist btw and he is a big advocate of brushing the teeth of our pets.

  12. Here's a zoo dentist:

  13. Yes, pets have teeth problems are well. Even carnivores like dogs and cats are fed grains rather than meat. Many pet holders have no idea what they are doing: I recently saw dog food advertised for having lots of fibre. :-( That may be good for humans, if it is the right type, but carnivores do not need it.

    For real animals I would expect it to be rare, because, as you write yourself, it means you die. No dentist around. It would seem logical to me when these animals with poor teeth were suffering from malnutrition.

    It is perfectly natural that you require more evidence than I need. In this debate I am not the scientist, thus I do not have more. Maybe I had more which I switched my diet. I am happy with my current one and no longer read much on diet any more.

  14. Wild carnivores like leopards and cheetahs don't actually live for very long - 10-12 years and so their teeth last long enough for them to produce the next generation. But they can still suffer from tooth decay. I agree that domestic dogs and cats probably have more dental problems than their wild counterparts because of the diet we feed them but they also tend to live for longer.

    Here's another zoo dentist checking the teeth of dolphins and cheetas:

    I suspect animals in zoos live for longer than wild animals and so keeping their teeth in good condition is more important. I'm not sure what they feed cheetahs and dolphins in zoos but I imagine they would go to some effort to make it as close to their natural diet as possible. I doubt dolphins are fed a vegan diet :)

    It's also wrong to think that Neanderthals and early modern humans did not eat grains. They've found evidence of grains on their teeth:

    "Our data comes from the analysis of plant microremains (starch grains and phytoliths) in dental calculus and on stone tools. Our results suggest that both species consumed a similarly wide array of plant foods, including foods that are often considered low-ranked, like underground storage organs and grass seeds. Plants were consumed across the entire range of individuals and sites we examined, and none of the expected predictors of variation (species, geographic region, or associated stone tool technology) had a strong influence on the number of plant species consumed. "

  15. Humans nowadays have teeth problems well before reproductive age. That does not seem normal to me except in hard times. Given the variability of the climate and ecosystems, most times should not be near the edge for most.

    People in the stone age, when they reached adulthood, could easy become 50 years old. So anything that happens to your or my health is not normal, especially because we do not live in hard times.

    I do not know whether it is this study, but there was a study where the word "grain" was interpreted wrongly. Grain can also mean a piece. Like a grain of salt. Thus your quote does not have to mean that the starch came from a grain.

    That plants are a normal part of our nutrition no one will deny, especially when we started cooking and could neutralise the many plant toxins present in plant foods. We can, however, also live on a very high animal product diet, as the Inuit or Masai show; that may require genetic adaptation, not sure if this is something for anyone and it is at least needlessly expensive and bad for the environment.

  16. That particular study is not the only source I've come across which says early humans ate grains. There's a good TED talk from anthropologist, Christina Warinner, and she explains how her team have been able to examine the fossilised dental plaque on the teeth of early humans. They have actually extracted and analysed the DNA from this plaque and found barley, legumes, and tubers.


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