Ask just about any mainstream physician or nutritionist why so many people are so overweight and I’ll give you 20 to 1 that the answer will be: people eat too much and don’t exercise enough. The eat-too-much-don’t-exercise-enough drum has been beaten so often that almost everyone has fallen into step. In her column in today’s New York Times the much despised Jane Brody harps on the issue in her own authoritative way. After giving a slight nod to the possibility of a genetic basis for obesity Ms. Brody writes:
But genes do not account for the doubling and tripling of obesity rates among both adults and children since the 70’s. For this there is only one possible explanation: the environment in which our genes are forced to act — the foods people eat, how they eat them and how they expend the energy their bodies do not need. (my italics)
Ms Brody goes on in her article about the excess calories that most folks eat thanks to the large portions served at most restaurants and the general taste that people have for calorically dense foods. She makes the case in a not-too-subtle fashion that we all should be eating more fiber, more salads, more fruits, more of everything that is not particularly filling or satisfying. And she believes in the vital role of exercise as a weight-loss tool despite the accumulating mass of scientific literature showing that exercise–at least in the quantities most people are willing to do–is pretty much worthless in terms of losing weight. Exercise has without a doubt a multitude of health benefits; significant weight loss just doesn’t happen to be one of them.
Given the constant blather I hear from people about how they’re going to lose weight–some by following a Jany Brody kind of diet, others planning to exercise their avoirdupois away, others by both–I’m reminded of something Woody Allen once said:
More than any time in history mankind faces a crossroads. One path leads to despair and utter hopelessness, the other to total extinction. Let us pray that we have the wisdom to choose correctly.
What if Woody is right (at least as his quote would apply to weight loss)? What if cutting calories and running yourself ragged exercising don’t work because, well, you’re not overweight because you eat too much and don’t exercise enough?
A group of scientists from multiple institutions looked at a number of other reasons that we could be in the midst of an obesity epidemic that have nothing to do with diet and exercise, or as they call them, the Big Two. They make the case in an paper published online in advance of print in the International Journal of Obesity that so many have so fully accepted the Big Two that pretty much no one has bothered to look for any other causes. As they jay out their paper…
We highlight evidence showing that the obesogenic influence of the Big Two is largely ‘circumstantial,’ relying heavily on ecological correlations rather than individual-level epidemiologic data or randomized experiments. Subsequently, we delineate the evidence for 10 other putative factors for which the evidence is also circumstantial but in many cases, at least equally compelling. We conclude that undue attention has been devoted to reduced physical activity and food marketing practices as postulated causes for the epidemic, yielding neglect of other plausible mechanisms.
The authors go on to discuss the evidence for the Big Two, skewing their list of evidence toward that that doesn’t particularly show a correlation. They then get to the other ten possible causes of the obesity epidemic and discuss how these factors made the top ten list. Their logic is that they looked for factors that have both been shown to have an effect on fat accumulation and that have increased in similar fashion over the same time period that the obesity epidemic has been developing.
Here is a graph from the paper showing the ten factors and their association with the increase in the prevalence of obesity since 1960.
Let’s consider these ten factors as the authors present them. I’ll make my comments as we go along; feel free to comment yourself.
Factor # 1: Sleep debt.
The authors state the case that studies have shown that sleep is inversely related to BMI and obesity and that, in the case of animals, sleep deprivation produces overeating. They point out a number of endocrine changes that occur with sleep deprivation that are also associated with weight gain. They present data showing that the average amount of sleep has steadily decreased over the past several decades from an average of over 9 hours per night in adults to just over 7 hours.
I suppose there could be some merit to this factor, but my guess is that the sleep deprivation is probably caused by the obesity or that a third factor may cause them both. Let me explain. As with obesity we are in the midst of an epidemic of gastroesophageal reflux disorder (GERD) worldwide. As I posted earlier, it appears that GERD, like obesity, is driven by excess carbohydrate intake. Victims of this disorder commonly awaken at night with severe burning chest pain and sometimes even regurgitation of acid into the throat. The decreased sleep associated with obesity could be a manifestation of the associated disorder GERD and not a cause of the obesity. Also, in today’s world people seem to be more stressed than ever, a situation that causes many to be unable to sleep through the night. The associated constant release of cortisol as a consequence of chronic stress can also cause the accumulation of excess fat. In this last case the stress would cause both the sleep deprivation and the obesity.
Factor # 2: Endocrine disruptors
Endocrine disruptors (ED) are environmentally stable (i.e., not degraded over time), industrially produced chemicals that concentrate in fatty tissue and affect endocrine function in a way that leads to fat accumulation. Many of these chemicals are pesticides and fungicides that are in constant use and contaminate not only the food we eat but the ground water as well. The problem is that since we haven’t had millenia of exposure to these dangerous substances, we haven’t developed a way to get rid of them. As with most toxic chemicals that make their way into our bodies, they tend to get shunted to fat where they tend to concentrate over time. I have read enough papers lately on the consequences of the buildup of these chemicals in all of us that I believe there really is something to this factor. Human studies have definitely shown that the ED burden has definitely increased over time and that an increased ED burden correlates with excess fat accumulation.
The ubiquity of these EDs is the primary reason we advocate organic food. We can’t do a lot about many of the chemicals that we come in contact with be we damn sure can refuse to eat them. Many vitamin and anti-oxidant-filled fruits and vegetables that are conventionally grown (strawberries come to mind) are loaded with endocrine-disrupting pesticides, making them best avoided. Unfortunately, even scrubbing these foods doesn’t eliminate the pesticides; in many cases even peeling the fruits or vegetables doesn’t hack it. The bride posted on this issue a day or two ago, so you can click here to see the worst offenders. If I did nothing else, I would at least avoid the produce on this list unless it was organically grown.
One of the biggest offenders is butter, which makes sense when you consider that the cream from which the butter is made is a fat that has concentrated the pesticides in the cow. We always use organic dairy products for this reason.
Factor # 3: Reduction in variability of ambient temperature
This is kind of a weird one. The authors explain that the thermoneutral zone (TNZ) is the temperature range at which we don’t need to expend energy just to maintain our body temperature. At temperatures above and below this range we have to spend energy to either heat ourselves up or cool ourselves down. And if we have to spend energy to maintain our body temperature, then that energy can’t go into stored fat, and, ergo, we don’t gain weight. The authors point out how farmers regulate the environment to maximize weight gain and how studies in both humans and animals have shown how temperature excursions above the TNZ markedly reduce food intake. They discuss how more people the world over are spending most of their time in the TNZ thanks to more universal heating and air conditioning. They provide statistics indicating that in the Southern US, the area with the highest obesity rates, the number of homes with air conditioning has increased markedly over the past couple of decades.
I don’t really buy into this factor although I had some recent first-hand experience with the loss of appetite that accompanies an excursion above the TNZ. MD just had her high school reunion in Hot Springs, Arkansas and I went along for the ride. While she was hobnobbing with all her friends I was out playing golf in the 100 plus degree, 80% humidity weather. On all three days that I played, I ate bacon and eggs for breakfast and headed for the course. (All the morons that I played with inexplicably set the tee times at either right before or right after high noon, so we played during the worst heat of the day.) I played, drank plenty of water, and didn’t eat. And when I got back from the round I wasn’t particularly hungry. In fact, on one of the nights I didn’t eat anything at all. I noticed at the time that somehow the heat took away my hunger, so I was keenly interested when I read about same in this article.
I don’t really buy this factor as a major driving force in the development of the obesity epidemic for a couple of reasons. One of the areas that has the least obesity is Southern California, and Southern California stays gloriously in the TNZ most of the time both day and night. New Orleans on the other hand is a hell hole temperature-wise. According to the statistics quoted by the authors of this paper the number of homes without any air conditioning is around 7%. One would have to assume that these 7% of homes were occupied by people living at the poverty level. When Katrina struck last year, so the talking heads on TV told us, only the most poverty stricken were unable to flee before it. So, you’ve got to figure that a lot of the people stuck in town were the same people who lived in the 7% of houses without air conditioning. And, at least in the coverage that I watched, virtually all of these people were obese.
Those who live in hot areas without air conditioning adapt to it. They take siestas, they get up early in the morning, they stay up late at night when it’s cooler, and, all in all, strive to live their lives as close to the TNZ as they can. I don’t really believe that in the long run the fact that we live in air conditioned houses and work in air conditioned offices makes us obese. I’m willing to be persuaded if I see the data; I just haven’t seen it yet.
Factor # 4 Decreased smoking.
Everyone knows that if you smoke and you quit, you are going to have to fight gaining weight. The New York Times had an article today quoting a recent study that showed that ex-smokers actually gain more weight than had previously been thought. The old data show a gain of from 5-15 pounds; the new data increase that to 20 pounds. There is no doubt that many, many more people smoked 50 years ago than do today, and there is no doubt that there is more obesity today than there was 50 years ago. But, I don’t think we can blame the obesity epidemic on widespread smoking cessation. Had people all smoked for the past couple of hundred thousand years and then decided to start quitting over the past 20-30 years maybe, But smoking is a recent phenomenon in the development of man, and several hundred years ago before smoking started in Europe obesity wasn’t a big problem. I don’t think we can blame it on people deciding to quit now.
Factor # 5: Pharmaceutical iatrogenesis
Iatrogenesis, the causation of a state of ill health brought on by medical treatment, is indeed a cause of weight gain. Multiple drugs commonly given for a host of medical disorders have weight gain as a side effect. Antihistamines, antidepressants, anticonvulsants, blood pressure medicines, diabetic medicines, steroid hormones, mood elevators, birth control pills–all have been shown to cause weight gain to varying degrees. The authors make the case that there has been a huge increase in the number of people taking these drugs–especially the antidepressants and mood elevators–over the same time period as the obesity epidemic has been developing. Once again, I think there may be other factors afoot that cause both.
MD and I have always noticed that at the same time the bookstore shelves were laden with books on low-fat dieting they were also filled with books on depression. I don’t think this is a coincidence. The brain is a fat dependent organ composed primarily of fat. An enormous number of scientific studies have shown that people who don’t get enough fat nor enough cholesterol tend to develop depression and/or anxiety. MD and I have seen this first hand. Ten or so years ago we participated in a clinical study for an anti-obesity drug that worked by inhibiting fat uptake in the gut, thereby putting patients on a low-fat diet irrespective of how much fat they actually ate. One of the big problems we had was that the patients on the drug became depressed, anxious, or both, went to their regular doctors and were given prescriptions for antidepressants or anxiolytic medications. One of the guidelines of the study was than anyone who took one of these medicines was disqualified from continuing. We fought this problem continuously, so we know that low-fat diets cause mental problems. During the past 20 years the average fat consumption has fallen about 25%-30% as the obesity epidemic has surged, leading, I’m afraid, to a whole lot of antidepressant prescriptions. I would have to say that the increased drug use doesn’t cause obesity, but is, like the obesity epidemic, a consequence of a sea change in the American diet.
What about antihistamines, blood pressure medicines, anti-diabetic medicines? Same thing. When people get fat, they have more allergies, asthma, high blood pressure and diabetes. The dietary changes cause both the obesity and the attendant problems requiring drug treatment.
Factor # 6: Changes in distribution of ethnicity and age
The authors are making the case here that older people tend to weight more as do African Americans and Hispanics in general. Since the percentage of the population representing the older people, African Americans and Hispanics is growing, then one should expect to see and increase in the rates of obesity. Or so it would seem to make sense if the obesity increase were limited to those groups only, but unfortunately the rates of obesity have been climbing in all age groups (had doubled in the pediatric age group, in fact) and all ethnic groups. I think this factor may make up a tiny bit of the increase in obesity rates overall, but not much.
Factor # 7 Increasing gravida age.
More women are waiting to have children and more women are having children at later ages. Studies indicate that older women tend to give birth to children who are more overweight later in life than those born to younger moms. It is true that older mothers produce children who tend towards the overweight later in life, but why is that? It’s because older mothers tend to be more obese than younger mothers, and all the endocrine abnormalities that go along with being overweight influence the endocrine systems of the developing fetuses. So to attribute the increase in obesity to this factor is like saying that the reason there are so many obese people is that so many people are obese. Unless you’re a politician, this kind of reasoning doesn’t hold any water.
Factor # 8 Intrauterine and intergenerational effects.
This factor basically lays the sins of the fathers and grandfathers (and mothers and grandmothers) on the intrauterine development and subsequent obesity of later generations. There may be some validity to this factor, but not enough ( I don’t believe) to cause the current obesity epidemic. Some animal overfeeding studies have shown that overfed animals tend to produce overweight progeny several generations on, but if you think about it, it’s easy to see what’s going on. It is well known that eating a lot of refined carbohydrates during the first trimester leads to babies with overdeveloped pancreatic beta cells, which makes sense since these cells are developing at the same time the mother’s blood sugar is elevated due to the high-carb diet and are bathed in the same sugary blood. As these babies reach adulthood they are more prone to insulin resistance, blood sugar problems including diabetes, and obesity than their peers who don’t have the same congenital problems. These kids with glucose, insulin and obesity problems pass them along to their own offspring in the same way they got them themselves. I believe this factor is a result of the obesity epidemic; not a cause.
Factor # 9 Greater BMI is associated with greater reproductive fitness yielding selection for obesity-predisposing genotypes.
This factor makes the case that obesity is heritable and that obese people reproduce more prolifically than do lean people leading to an ever increasing population of the obese to continue passing on their obese genes. There is a correlation between obesity and socioeconomic status and a correlation between economic status and number of children, i.e., the poor tend to be fatter and to have more children. But is that the underlying cause of the obesity problem in general? Is it simply a matter of genetics? I don’t think so. Up until about WWII the situation was reversed. The poor were not obese, they were underweight simply because they didn’t have enough to eat because they couldn’t afford it. When people don’t get enough to eat, they don’t get fat, even if genetically predisposed. Now food is cheap, cheap, cheap and even the poor can overeat without spending much money. I read a few weeks ago that the percentage of the average American’s income that was spent on food in the early 1950s was about 25%-30% and most of this food was prepared and consumed in the home. Today the average percentage has dropped to 14%, a great deal of which is consumed in restaurants.
A misconception about genetics is that if one is genetically predisposed to something that that something will assuredly take place. Not so. The conditions must be right to trigger the genetic response. We have the same genes today that we had 100 years ago when practically no one (except the rich who could afford a lot of food) was obese, but now were obese in record numbers, especially poor people. Something has happened to fire off the genes we do have, and I believe it is the change in diet and maybe a few of the other factors previously mentioned, i.e., endocrine disruptors.
Factor # 10 Assortive mating and floor effects.
In short this factor posits that fat people tend to marry other fat people and, consequently, produce fat offspring, all of whom contribute to the obesity epidemic. As the authors point out the correlation between BMI and other ‘adiposity indicators’ is in the range of about 0.15, which is small but statistically significant, leading over the long haul to an increase in obesity. I don’t know how much faith I put in all this. It’s probably true that most people marry within their socioeconomic class, and since there are many more poor than rich people, and since poor people tend to be more overweight, it stands to reason that with time more people will be obese. But, it’s not really a consequence–I don’t believe–of so-called assortive mating, but a consequence of less well off people consuming calorically-laden diets high in carbohydrates and bad fats, i.e., fast and processed foods.
Were I putting together this list I would surely have added the idea that obesity could be of infectious origin. The explosion in prevalence of obesity over the past 15-20 years certainly looks like an infectious disease epidemic. Probably a dozen infectious agents are known to cause obesity in animals. Why not in humans? I read a paper not too long ago in which the stored blood of several hundred people were checked for antibodies to an adenovirus that causes cold-like symptoms. As I recall about 30 percent of obese people had antibodies to the virus whereas only 11 percent of normal weight people had them. I would bet that when all the information is in, we find that viruses or Chlamydia-like bacteria drive a certain portion of the obesity problem.
Despite the correlations that the authors found with these ten factors and even the additional factor I added about the infectious agents causing fat accumulation, I still believe that the majority of the obesity we see is of dietary origin. Why? Simple. Because it responds to dietary changes. Take any number of people who are obese, put them on good whole-food low-carbohydrate diets and they lose weight. If they stay on a maintenance version of the same diet, they keep their excess weight at bay. It doesn’t seem to matter whether the weight came as a result of endocrine disruptors, drugs, living in air conditioned houses or whatever, it all comes off with rigorous following of a proper diet.
Deep within our modern cell-phone toting, processed food eating, lazy, air conditioning loving, sleep-deprived, endocrine disrupted bodies idles the same ancient metabolic processes that kept our Paleolithic ancestors lean and fit. All we need to do is provide the proper raw materials, then stand back and watch the magic happen.
* With apologies to Elizabeth Barrett Browning
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