Thursday, January 27, 2011
Obesity: Conventional Wisdom Trumps Science, Again.
Scientific American usually has well-written, interesting articles by experts in their respective fields. This article, being the cover article and all, fell very short of my expectations. While the biology, especially, the molecular biology of obesity is very complex, I was very disappointed that the author, David Freedman, quickly glossed over the physiology to spend the remainder of the article discussing behavior modification and promoting Weight Watchers. I thought I was reading Time magazine, not Scientific American.
Most, including Freedman, are sold on the idea that obesity is simply taking in more calories than you burn, and weight loss is simply burning more calories than you take in. That is, the first law of thermodynamics (conservation of energy) can not be violated. But, if you look at the research, the results show a great variability in amount and rate of weight loss with nutrition interventions. And over the long-term, very little success. Instead of trying to reason that the subjects cheated, perhaps it is time to reevaluate the idea that excessive calories causes weight gain, and caloric restriction causes weight loss. Instead, and what I would have liked to see in this article, is what factors regulate storage of fat in fat cells. Because it is not all simply excessive energy. There is much support for that. The key factor missing in the conservation of energy argument is the neuro-hormonal regulation of energy. The human body is not a closed, isolated system (the requirements for the first law of thermodynamics). And stored energy (fat) can only be used for energy if it is released from the fat cells (hormonal control). This is the important science that we have bits and pieces of, but wished were explored more in this article. Energy regulation in the human body, we know, is much more complex than simply calories in vs. calories out.
There are so many examples of this complex neuro-hormonal regulation. Puberty in boys is a great example. Although, nutrition intake can influence lean muscle mass and fat mass composition change to some extent during puberty, ultimate regulation is under hormonal control. Without changing anything, a boy can gain a significant amount of muscle mass and lose a significant amount of body fat during puberty. Interestingly, the hormonal changes cause an increase in appetite. The increase in calories intake does not cause the changes in body composition. But, if you use the obesity logic, you would conclude that the increased calorie consumption caused the dramatic change in body composition.
Insulin therapy in new diabetics is another lucid example of the the central role hormones play in fat storage and use. Just about all diabetics gain body fat after they start insulin therapy. Why? Well, now the blood glucose can be signaled to be stored in the body fat as opposed to staying in the blood or spill into the urine, even without dietary changes.
There are many other examples of the critical role of hormones in the regulation of body fat that shouldn't be ignored. Body fatness is correlated with less sleep, refined carbohydrate intake or glycemic level, and cortico-steroid therapy. Additionally, strength training is rarely recommended as an inexpensive, efficient, and safe treatment for obesity, though it has a profound effect on the hormonal regulation of energy stores in the body.
These and many more examples should be enough to encourage us to use science to look beyond the calories in vs. calories out theory. Nutrition science, like physics and chemistry research should be rigorously challenged, not simply accepted on face value because it is simple. This was a great opportunity for SA to take the next step and delve more deeply into the complex biology of obesity and energy regulation. Only with this knowledge can our education and behavior modification programs be even more successful.