Epidemic Obesity: Adaptation Gone Wild

Obesity is unnatural, but it’s natural to try for it.

titian_venus_mirrorThis morning I sat on a panel for medical students; the subject was obesity. Nationally, as anyone who hasn’t been hiding under a rock knows, the picture is not pretty-in fact it’s pretty ugly. By the standard definition, obesity means a Body Mass Index (BMI; weight in kilos over height in meters squared) above 30, and in about 15 years starting in 1990 we went from 22 percent to 33 percent obese.

Now, I don’t care what you call it or where you want to draw the line. Pick any BMI number and you’ll see more Americans above it every year. This includes children and teens, who are showing up in pediatricians’ offices in growing numbers with Type II diabetes, which used to be called “adult-onset.” In some practices there are more of them than there are of Type I, once called childhood diabetes.

Don’t want to call it an epidemic of obesity? Fine. Endemic, pervasive, skyrocketing, steeply increasing, whatever. Anyone who’s telling these kids that it’s okay and they should feed good about their bodies is doing them and the country a huge disservice. They are headed for diabetes, heart disease, colon cancer, arthritis, and many other conditions in record number. Help them with their body image issues, but don’t tell them it’s fine to be fat.

But why this trend? Isn’t it maladaptive? In evolutionary terms, the answer is simple. Not just for millions but for hundreds of millions of years our ancestors were selected to store fat during times of abundance. That way, you could survive lean times. Trouble is, now there’s no end to abundance.

Among the Bushmen of Botswana, who I lived with for two years, and other hunter-gatherers, there was no starvation but there was also no obesity. Foods were harder to get, eat, and digest, and they maintained a high level of aerobic and muscular fitness just because of activity in the food quest. Compared to our diet , theirs was much higher in fiber and much lower in refined carbs, saturated fat, and salt. Children were always outdoors and active.

Our genes and bodies evolved in that context, and they just can’t handle what we do to them now.

Culture matters, of course. My colleague Peter Brown and I many years ago looked at the ideal of beauty in cultures throughout the anthropological record. Plumpness is the ideal in over 80 percent. Look at paintings by Rubens, Titian, and Tintoretto, and you’ll see the women who were considered the greatest beauties of their time. Other eras have prized less plump women, but few thin enough to make Playboy, much less Vogue.

Slim was the ideal in a few cultures, very fat in none. Pleasantly plump but not obese was the goal in most, and the extra fat those beauties stored held just about the extra energy they would have needed to get through a pregnancy and a couple of years of lactation. In other words, they were beautiful because they could make and nourish a baby.

In some cultures in the past, frank obesity was evidently valued. Carvings like the “Venuses” of the late Stone Age looked like women with very high BMIs, possibly also pregnant. Some cultures in Africa had fattening huts for adolescent girls to prepare them for marriage. In many cultures you displayed your wealth and status by showing you could put on surplus fat. But it stopped with pleasantly plump, probably because serious signs of ill health became evident when you went further.

But we live in the Supersize Culture, which is producing a legion of boys and girls, men and women, who are far fatter than the plumpness that used to be (and in much of the world still is) the norm. Yet ironically ours is a culture with a cosmetic ideal that’s uniquely thin. It’s not a health ideal; mortality is lowest at a BMI of 22 or 23, which you would never see in a typical fashion ad. And at its worst the ideal leads to anorexia or bulimia.

Those are bad, sometimes deadly disorders, but the implications for the population are far more dire at the other end of the BMI spectrum. And like most bad things, the trend is worst for the poor. Our society consigns the poor to put on weight by making it hard and expensive to get good food and easy and cheap to get junk.

The trend affects Blacks (especially women) more than Whites, in part because of culture but mainly because of access. You can’t find fresh fruit and vegetables in the inner city, and you don’t want your kids playing outside on streets rife with drugs and gunfire. You’re struggling to keep body and soul together, so when your kid sits for hours watching TV and eating snacks, you’ve got bigger worries than BMI.

But it’s up to us as a society to recognize that there is more going on here than lack of will power. The human species was set up to store fat whenever possible and to resist weight loss with many fail-safe appetite mechanisms. And for very good evolutionary reasons, it’s even harder to keep weight off than to lose it.

So we’d better rethink our laws, school food policies, farm subsidies, educational programs, and information campaigns before we have to change our name to Homo lipidens.

Note: By invitation, I’ve started a blog on the Psychology Today website , and my latest post can be read there or here, although different comments may be  posted there.


  1. Clare says:

    I completely agree that the biological bases of obesity are poorly understood by many people concerned about obesity. Where finding solutions becomes tricky is that the biology of eating, and the socio-cultural entailments of eating (particularly in creatures biologically given to symbolic thinking) are so complexly intertwined. I am stepping out of my area of expertise here, but would it be right to suggest that food sharing and communal eating (eating with at least one other person, even if there are rules that dictate some people can’t eat in the presence of certain other people) has probably helped manage food consumption for a very long time in human beings? And then there is the association of foods with certain conditions, life stages, rituals, etc. that also regulates their intake. This can on occasion be detrimental as well as beneficial, as when food distribution and consumption are rigidly controlled. But what we see in the US today — not just monstrous portions of high fat, high sugar food — but solitary individuals eating without company, and at speed, shows what happens when the social contexts of eating become extremely impoverished. Just a thought….

  2. Mel Konner says:

    Dear Clare,

    I like this thought, although I think it’s complicated and depends on the cultural context as you say. There are studies that show that Americans eat more when in some social situations (especially parties), but very obese people are known for solitary eating, sometimes meal after meal after meal in succession in different fast food places. Eating faster does encourage overeating, probably because it takes time (perhaps 20-30 minutes) for some satiety signals to kick in, so if you’ve eaten more slowly you will have eaten less.

    The French apparently follow your hypothesis, eating more slowly and deliberately than Americans in settings where they are conversing extensively — more time between bites as well as slower, more thoughtful chewing, which allows them to savour their food instead of just eating to fill their stomachs. This pattern probably satisfies appetites in ways unfamiliar to most Americans.

    However, often saw Bushmen gorge themselves on meat right after a kill, eating a huge amount in a short time. Perhaps this is an adaptation to getting what you can before you have to share or have it stolen from you by other predators. They’re just unlikely to get fat however much they gorge on a given occasion, because the occasions are not frequent enough.

    So yes, culture matters a lot, in various ways. But endemic obesity is now worldwide, even in the wealthier sections of populations that have many starving people. I read that the French cabinet surveyed their own growing problem and someone said, we’d better watch out or we’ll become like the Americans.


  3. diana says:


    “But why this trend? Isn’t it maladaptive? In evolutionary terms, the answer is simple. Not just for millions but for hundreds of millions of years our ancestors were selected to store fat during times of abundance.”

    I should lay my cards on the table at the outset. I was obese as a teenager. At 55, my weight is normal (although I would like to be 10 pounds thinner for cosmetic reasons…..) Because of this, I have a life-long obsession with weight. Ironically, while society has become fatter, as a middle-aged woman I am now on the lean side. It’s weird for me as an adult to look at all the fat teenagers. It really should be the other way around.

    How did that happen? As a teenager, I binged on sugar. I gradually stopped and my eating habits normalized. I lost weight here and there and after about 10 years, I was 50 pounds lighter.

    Another confession: I am a firm believe in the low-carb theory that insulin spikes cause fat storage. I believe that the reason I was a fat teenager was because I binged on sugary foods. I also believe that most fat people in our society secretly binge. I think if you were a fly on the wall, you’d see very different eating habits than what people report. Who is going to admit that they ate a gallon of ice cream? And after they have messed up their metabolism by bingeing, it doesn’t take much eating to keep the fat on.

    Your bushmen who gorged on meat didn’t get fat because meat doesn’t affect your insulin levels the way carbohydrates do. Same goes for Eskimos who ate loads of fat, Aborigines who ate loads of fat and meat, etc. Fat and protein aren’t metabolically the same as carbohydrates! A calorie is metabolically NOT a calorie.

    I know that you’ll object to my comments by pointing out that Chinese and Japanese people eat high carbohydrate diets and have low rates of obesity. After thinking about the subject for a long time, here is my answer to that.

    I do think that you can say there are “good carbohydrates and bad carbohydrates.” Refined sugar is super-palatable to many people (me, unfortunately) and makes us binge. The vast majority of East Asians don’t binge on their food. They eat to satiety, which they have adapted to do for thousands of years, and then stop. Their insulin levels aren’t spiked. They don’t eat a lot of sugar, and they maintain a normal weight. (They also smoke a lot, and this has been shown to release fatty acids into the bloodstream…..)

    Obesity is on the rise now in China and Japan – they are also eating more refined sugar? Think there’s a relationship. I sure do.

    So, Mel, I don’t think it’s a simple question of adaptation – I think that some of us are inclined to get addicted to a certain very addictive food, which was formerly not available in huge quantities. Now it is.

    I think that if by some miracle every bit of sugar was vacuumed up diabetes rates would go down and the obesity epidemic would be a bad memory.

    Hard to read tables:




  4. diana says:

    PS, An addendum to the above. I think I’ve made my point that we weren’t really selected to store fat, we just weren’t selected to eat refined sugar, which is very bad for most of us. With that in mind, I don’t agree with you that the ideal historically in most societies was “pleasantly plump”. Maybe that was true in the Dutch Golden Age (Rubens, etc.) but where else? And by the way, when you look at Rubens’ ladies, they are very firm, and their breasts are pretty small. I think Rubens was just exaggerating a bit for emphasis.

    I’ve traveled to quite a few countries, and the ideal for young women is always the slender hourglass figure, firm breasts, rounded hips. Class is involved to a degree, it seems that the more exposed to aristocratic tastes people become, the more they develop a taste for height and slenderness in women, which is an interesting idea to contemplate. (Also aristocratic tastes create an obsession with female beauty, as opposed to run of the mill prettiness.) In East Asia the ideal is downright slender, and I don’t believe that classical Chinese or Japanese ideals of female beauty ever focused on breasts.

    So, I certainly agree that fetishizing skinniness is aberrant, but not slenderness.

  5. Mel Konner says:


    Your comments here are exceedingly thoughtful and I appreciate your taking the time to share them. It sounds as though your personal experience has a lot in common with mine. I was chubby as a boy, became slender at 16 or so, became chubby again in my late ’40s, and then lost 50 pounds over four years (in fits and starts, not smoothly a pound a month) and have kept it off for a decade. As for the last ten pounds, they’re a different story, in my view because natural selection (nature) made our bodies scream bloody murder when we get that close to the edge. (My cousin Linda Konner wrote a book called The Last Ten Pounds.
    She’s gorgeous and I love her dearly, but the book didn’t get the last ten off either me or her.) As for the plumpness ideal, it’s not about modern nations, even modern urban Asia. Go to Mongolia or Provence and look at well-to-do rural women. We looked at cultures throughout the anthropological record. Some like slender, some like fat, but the plurality like pleasantly plump.

    As to the low-carb diet point, I have to say I am reserving judgment. A couple of days before you posted your comment a study appeared in the Annals of Internal Medicine showing higher mortality on the Atkins diet. Dean Ornish (okay, not completely objective) summarized the evidence here:
    The new study is here: http://www.annals.org/content/153/5/289.abstract
    I know the Eskimo eat blubber by the pound and the Masai drink whole mild and blood, and I don’t know how they avoid cardiovascular disease and neither does anyone else. But most hunter-gatherers got more plant foods than meat, with a modest amount of animal fat. However, except for small doses of honey, there was nary a sugar or refined carb in sight, and it had fiber levels that would make most Americans uncomfortable.

    I favor a diet that is mainly vegetables and fruits with substantial (not Ornish-like) amounts of lean meat and fish. That’s my story and for now (show me the evidence and I’ll change my mind) I’m sticking to it : }

    Thanks for reading and for your very thoughtful comments.


  6. Angela says:

    The publishing date for this post has long past, but here’s to hoping that someone like me will stumble upon it later and take a peak at the comments.

    I agree with Diana in that we are not selected to store fat. There were plenty of hunter/gatherer groups, and even post-Neolithic societies, that had abundant food if they wanted it. You can even say this about the US before 1970. However, people were just not putting on the weight the way we are now. In fact, it would have been an evolutionary DISadvantage to do so– think about running from an animal, or TO an animal (hunting) carrying around a spare tire. What has changed is not how much food is available, but WHAT food is available.

    Saying that our food has become “high fat” is totally false, especially if you qualify that fat as saturated. Many hunter-gatherer groups were eating plenty of fatty animals, especially since they ate all parts of the animal, including the cholesterol-rich liver and fatty marrow. And pastoralist wouldn’t have touched all the low-fat dairy that has taken over our society. And don’t even get me started on the boneless skinless low-fat chicken breasts. Most estimates put the fat percentage of indigenous groups much higher than the current US diet estimates, with the percentage of calories coming from animals higher than those from plants. And just look at the USDA numbers: our consumption of animal fats is being replaced by omega-6 rich vegetable oils. These oils didn’t exist before we invented them in the 1900s. The ratio of omega 6 fatty acids to omega 3 has gone from around 1:1 (hunter gatherers, pastoralists, maritime groups, etc) to about 17:1 (Standard American Diet). I’m just pointing this out so we stop wrongly fingering saturated fat at the culprit.

    What’s ruining our health is not “more” food, but “new” foods. So much fructose (from refined white sugar and HFCS) has never been so abundant in the human diet. The same can be said of vegetable oils (high omega-6). You could even say the same about grains, specifically overly-processed gluten grains. Most cultures (throughout Latin America, Asia and Africa) did not consume wheat until recently. We’re eating more grains than ever before, and we have even created wheat crops that contain double the gluten. Our research on this is so scarce, but we’re learning how this plant protein changes small intestine architecture and creates low-grade inflammation. We’re now eating about 60% of our calories from three grains: corn, wheat and rice (of course, calories from vegetable oils and fructose count in this). All from plants, these three agents (fructose, linoleic acid and gluten) are probably responsible for the “diet” slice of the problem pie. Not saturated fat, not meat, not cholesterol, not salt. Of course, there are other pie slices (food advertising, bad cultural practices, etc). But bottom line: the industrialization of the diet has ruined us.

    We didn’t evolve with the three agents I listed above. Our genetics haven’t changed since our diet became soaked in corn oil, our drinks loaded with HFCS. Our metabolisms can’t handle the new foods, and our brains completely succumb to the trickery of these new foods (you can call them professionally created, since lots of brain power from scientists and the like go into making these foods irresistible- hijacking our reward system).

    Food for thought from a medical student.

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