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The Biggest Medical Myth of All Time
Without a doubt, the greatest medical myth of all time is that obesity, or any degree of excessive body fatness, is the direct result of excessive food intake and/or insufficient exercise. Ask anybody. Literally. Ask 100 people, including scientists and health care practitioners, and 99 will tell you this. Ask 100,000, and 99,999 will give the same answer. The other one doesn’t speak English. Yet despite this widespread belief, there is no good research to back this up, and plenty of scientific evidence to the contrary. “Eat Less and Exercise More” I’ve heard it said that obesity must be the result of a caloric imbalance, because the First Law of Thermodynamics cannot be controverted, and indeed, this is the case. What people are failing to understand is that we cannot control our caloric balance via diet and exercise. Although we can adjust the amount of food we put into our mouths and how much physical activity we perform every day, our bodies determine what percentage of the available energy to use in the production of heat and physical energy and how much to store as fat. This is the real reason that overweight people often feel tired, sickly, and run-down—their bodies apportion input calories more in the direction of fat storage than energy production, and reducing calorie intake or increasing physical exercise only makes the situation worse. Let’s look at some numbers…or better yet, a few graphs (statisticians love graphs). Typical research studies on diet and exercise last three months. It’s considered a sufficient amount of time to measure significant changes in body parameters. Funny thing about three months, though—it happens to be just about the amount of time the average person’s body needs to completely adjust to a caloric imbalance. Here’s a graph showing what happened when a group of overweight people were treated with a medically-supervised, low-calorie diet, moderate exercise, and “behavior modification” program for longer than three months. I’ve looked at a lot of similar graphs over the years; the pattern is predictable—initial rapid weight loss, then slowing, then stopping. And all of this happens while still sticking to the original regimen. Of course, the diet “counselors”, friends, and family doubt that the patient is still sticking, but they shouldn’t. As numerous studies have shown, this is what will happen to 95% of overly fat people when a caloric deficit is created through diet and exercise. (We’ll cover the reasons why in another post.) So is life just not fair? Well, no, it is fair, because happily, the opposite relationship between caloric balance and weight also exists. That is, intentionally increasing caloric intake above current maintenance levels results first in rapid weight gain, then slower weight gain, and finally, weight maintenance at the new higher levels of both weight and calories. “Just push yourself toward the table!” Studies have shown that it is just as hard for an otherwise weight-stable person to gain beyond a certain level (~10% of current weight) and to “keep it on”, as the reverse. Notice the trend in this graph from an early study on the subject; weight is increasing, but less so with each passing week, and if one were to extrapolate (this study ended at 4 wks), it’s clear that the weight increase was approaching a level maximum. In what was probably the seminal study on the issue, E.A. Sims, an obesity researcher in Vermont, enlisted a group of naturally lean prison inmates to willingly overeat their way into obesity in order to study the effects of the disease as separate from the genetic factors that cause it. Well, much to his dismay, he found that, despite their best efforts—which included eating 6-7,000 calories a day and refraining from all work and exercise—the prisoners struggled to add and then retain the requisite 25% to their weights, even though they were eating 200% of their previous intake. One particularly lean fellow could never gain more than twelve pounds (9% of his initial weight) after months of stuffing his face and lounging around in his striped pajamas. In an alternate universe where “Weight Watchers” is a support group for overly thin people trying to bulk up, this poor guy would have been labelled lazy, undisciplined, and probably stupid, as well, for not doing what was needed to meet his weight goal. “Energy is neither created nor destroyed…” So now we might be agreed that diets do not continue to cause weight loss, but many would argue that they can still be used to cause some weight loss, which could then be maintained by eating a “normal intake” (which assumes the overweight eat more than the thin to begin with—an errorneous assumption to be dealt with another day). Well, as it turns out, even a brief period of reduced calorie intake will cause the body to adjust its current level of “energetic efficiency”—the rate at which calories are partitioned toward energy versus fat storage. Let’s see what happened when a group of rats decided to lose a few for bikini season. In a cleverly designed experiment by long-time obesity researchers Dulloo and Girardier, half of a group of young rats were put on a diet, while the others were allowed to eat whatever they wanted (the “ad libitum” group). The dieters were fed exactly 50% of what the ad lib group ate spontaneously, for a period of 30 days. At the end of that time, the dieting group was then matched to a third group of rats by both weight and body composition (that is, their total weight and percentage body fat were similar). For the next 25 days, the previously food-restricted rats were fed exactly what these similar-sized, non-dieted rats chose to eat naturally. If there was no adaptive mechanism, the two groups of animals would be expected to dispose of the calories in a similar fashion, but in fact, that was not at all what happened. Since they were young rats, they all gained weight during the 25 days of pair-feeding, but the gain and relative proportions of fat and lean tissue were vastly different, as the chart illustrates. The dieted rats gained the same amount of lean tissue, but more than twice the fat of their free-eating counterparts, on the same number of calories. This experiment clearly shows that the bodies of the dieted rats made not just minor, but rather gross adjustments to their calorie-burning efficiency and to the preferential deposition of lean and fat tissue. Thus, when dieters return to eating “normally”, where normal is the amount eaten by a person of similar size and body composition, they will lay down fat like nobody’s business. So what makes this seemingly implausible variance possible? That will be the subject of my next post, “The Calculus of Calorie Counting”.