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Tackling Obesity: Part 3: "Our Biology Is a Mismatch for Our Environment" 7.06.04 Source: Andrew Schwartz, for CHC exchange Genetic profiles are at least a few years off. In their absence, a number of biochemical insights have led to some promising screening techniques that can lead to better prevention. For example, Michele Mietus-Snyder, MD, a cardiologist who is associate director of UCSF Weight Assessment for Teen and Child Health (WATCH) program, speaks of "checking for clinical biomarkers, such as early indicators of chronic disease that we already know are associated with obesity." The WATCH clinic's Andrea Garber, a dietitian and researcher, mentions using early adiposity rebound to screen for at-risk children. Adiposity rebound is when the body's fat declines to a minimum before increasing again into adulthood. Typically it occurs between five and six years of age, but some studies have indicated that children who experience that rebound earlier (at age two or three), are more likely to become obese as an adult. Unfortunately, screening and prevention efforts must wrestle against a simple biological fact. "Our biology is a mismatch for our environment," says Bobby Baron, MD and program director of the UC Primary Care Program. "We're programmed to preserve weight, because we evolved in a time of limited food resources and hard physical work. This has to be explicitly acknowledged." Because our bodies have not yet evolved to meet the way our daily routines have changed over the previous century, our biology works against creating the precarious balance between food intake and energy expenditure. Pediatric endocrinologist Robert Lustig, MD believes that the mismatch has translated into a critical problem with the hormone insulin, which he calls "the proximate (biochemical) cause of obesity." Lustig's research has focused largely on hypothalmic obesity in children. While the condition occurs in only a small minority of cases, Lustig believes it provides an important window into the insulin problem. "Virtually every single one of these patients is hyperinsulemic," says Lustig, meaning that a disruption in the energy-balance pathway causes these patients to produce too much insulin. Or if the pathway isn't disrupted, the patients are what is known as insulin resistant-their body does not respond to insulin properly-and so they create excess insulin in response. In both cases, the body stores the excess insulin as fat. Lustig works with many such patients - and many others struggling with obesity - as director of the UCSF WATCH clinic. There he and his colleagues use something called an oral glucose tolerance test (blood tests after drinking a sugary beverage) as a screening tool for insulin response. Using the results, clinic staff then help these patients to reduce their insulin levels. Successes and insights gleaned in both his clinic and his research are what have led Lustig to his belief in the centrality of insulin in obesity. (See links to the rest of the six-part article below.) Part 1: Tackling Obesity |
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