“I think the obesity epidemic is really an unintended consequence of economic, sociologic, and technological changes that have occured around the world in the last 3 decades. The food supply has become very low in cost, extremely abundant, very powerful, and very high in caloric density. Labor-saving technologies have virtually eliminated requirements for physical activities as part of everyday life.”
That’s from Dr. F. Xavier Pi-Sunyer, speaking at during a plenary session at the annual meeting of the American Society of Hypertension. Dr. Pi-Sunyer is a giant in the field of obesity research — he chaired the committee of the National Heart, Lung, and Blood Institute that researched and defined the federal government’s new guidelines for the prevention and treatment of obesity. He has served as president of the American Diabetes Association, the American Society for Clinical Nutrition, and the North American Association for the Study of Obesity.
Ah, if only it were that simple. Of course, Dr. Pi-Sunyer was deliberately simplifying what has become a very big problem — not only in the United States but worldwide. Obesity touches most medical specialties. If we’ve learned one thing from obesity research in the last few years, it’s that —WOW — is obesity ever complicated! And it gets more complicated the more we look at it.
Anyone who has ever been on a diet has pretty much thought the same thing: calories in needs to be less than calories out. It’s simple thermodynamics. Anyone who has ever been on a diet knows that that is complete bunk.
As Dr. Pi-Sunyer obeserved at the beginning of his talk, obesity has economic and technologic factors. But anybody who watches TV knows that there are social factors. Those can be pretty complicated on their own. Raise your hand if you’ve ever watched a pizza commercial that was followed by a perfume commercial with dangerously thin models. What are you supposed to make of that?
There are psychological factors. I think Dr. Pi-Sunyer forgot all about the notion that these marvelous technology-based societies give rise to all sorts of disordered eating as a means of coping — admittedly in a “maladaptive” way — with too much information, too little time, and way too much STRESS.
We know that both environment and genes also play roles in obesity. But it also turns out that fat — itself — is very complicated. “We know now that adipose tissue is an endocrine organ … probably one of the most active endocrine organs in the body,” Dr. Pi-Sunyer noted. “There’s particularly a problem with intra-abdominal visceral fat … central obesity adds to the BMI problem. It adds a particular increase in insulin resistance and other mechanisms that clearly we don’t know all about.”
We also know that there is a very strong correlation between the amount of fat in the body and the amount of leptin circulating in the bloodstream. Insulin and leptin both play important roles in food intake regulation and energy expenditure regulation. Higher levels of both leptin and insulin tend to enhance the signals sent to the catabolic nervous system to decrease food intake and increase energy expenditure. And yet, “we know that obese people … are leptin resistant. Even though they have high leptin and high insulin, they don’t have a catabolic response as far as food intake is concerned,” said Dr. Pi-Sunyer.
To me, that sounds like he’s saying that once you pack on the pounds, those pounds work against you. It gets worse. Leptin and insulin resistance only scratch the surface of what we know about how obesity (adipose tissue) affects the body. Adipocytes (fat cells) produce a number of compounds that are involved in complex intermediary metabolism, including cytokines, tumor necrosis factor-alpha, interleukin-6, lipotransin, adipocyte lipid-binding protein, acyl-stimulation protein, prostaglandins, adipsin, perilipins, lactate, adiponectin, monobutyrin, and phospholipid transfer protein. We’re only beginning to investigate the interactions in the body involving these compounds produced by fat cells.
Is there an overweight gorilla in the room that we’re ignoring? Sure, healthy eating and increased physical activity are good steps toward losing weight. But is it enough for everyone?
— Kerri Wachter (on Twitter @knwachter)