A Deeper Appreciation of Evolutionary Medicine? Fat Chance

Article excerpt

WE'VE TRIED almost everything to get the weight off: low-fat, all-liquid, and no-carb diets; allegedly total gyms that fold like aluminum lawn chairs before sliding neatly under the bed; and shelves full of butt-busting, ab-crunching, cardio-crazy videos performed by disturbingly cheerful fitness models.

Doctors tell us that thirty minutes of moderate exercise three times per week will do the trick, but we know it won't. Apologists for the "big-boned" crowd claim it's all in our genes, or perhaps the collective fault of all the microorganisms living in our guts. Consumer advocates, celebrities, and politicians (or their spouses) blame fast food chains, television ads, school lunch programs, and even corner grocers for their failure to assume responsibility for other people's children.

So what are we missing? Well, any number of things probably. But if we seriously want to confront this "epidemic," as it's now called, maybe we need to dig a little deeper. Unless we try to "understand the how and why of human obesity," say biomedical researchers Michael Power and Jay Schulkin, and to regard it as "less the focus and more the example" of how human biology and modern environments interact, all attempts to treat obesity "will be problematic, if not doomed to failure."

In The Evolution of Obesity (Johns Hopkins, 2009), Power and Schulkin acknowledge the problem's incalculable complexity--perhaps much to the dismay of less motivated readers. Indeed, most biological systems shaped by natural selection consist of systems so interdependent on the one hand, and multifunctional on the other, as to completely defy cursory or clear-cut explanations.

Literally dozens of ancient information molecules link, regulate, or coordinate metabolism between cells or cells and end-organ systems. Peptides and steroid hormones, for example, connect the brain and the gut to regulate appetite and satiety in an attempt to synchronize behavior with digestion. And, somewhat surprisingly, scientists' perception of fat has changed dramatically in recent years. Once conceived as a passive product of positive energy balance (stored fat), adipose tissue is actually an endocrine organ that produces peptides, steroids, and immune-function molecules to actively regulate physiology and metabolism. "Many of the health consequences of obesity," the authors instruct, "are due to the metabolic effects of this endocrine and immunological organ becoming 'oversized.'" Why an epidemic? More than one billion people worldwide are now overweight or obese. In some countries, up to a third of the population is now considered obese, and in the United States--the current leader among developed nations--the condition's prevalence is three times what it was just fifty years ago. As of 2002, U.S. adults had become roughly one percent taller but 15 percent heavier since 1961, resulting in a mean body mass index (BMI) increase of 11 percent.

We've long known that obesity is associated with diabetes, hypertension, cardiovascular disease, and osteoarthritis. But recent research has revealed a connection to certain cancers as well. High BMI is associated with increased job absenteeism, and U.S. citizens dole out an estimated $61 billion per year for obesity related healthcare. In the end, severely obese people are 1.5 to 2 times as likely to die at any given moment as those with normal BMIs.

So given the stakes, one would assume we would zealously protect at least the most vulnerable among us. But U.S. children ate 43 percent fewer vegetables in 2002 than in 1978, and almost half of those eaten were fried potatoes. Bread, in fact, has become the leading source of carbohydrates for young people, followed by soft drinks. During the same twenty-five-year period, kids ate 425 percent more pizza and drank 70 percent more soda and 38 percent less milk. For both children and adults, processed and alarmingly fatty meats have become the norm. …