Monday, 19 March 2012

For Diet Rules for women

So what’s the message for women ­trying to lose weight?” asks ­Marcelle Pick, nurse practitioner and author of The Core Balance Diet. “That you’re doomed, and—good luck?” Pick thinks the story is more nuanced and not as grim as all that, but she’s not surprised when ­people are disheartened, particularly in the wake of a study published last ­October in The New England Journal of ­Medicine, the ­latest and most telling blow against the ­notion that American women in their ­twenties, whose average weight climbed about 30 pounds from 1960 to 2000, could slim back down with just a little more will­power. In that study, conducted at the Univer­sity of Melbourne in Australia, subjects who lost more than 10 percent of their body weight experienced a corresponding change in ­crucial appetite-regulating ­hormones such as leptin—and they ­never returned to normal levels during the remainder of the yearlong research periods. Why is that such a big deal? Produced by fat cells, leptin tells your brain’s hypo­thalamus whether your body’s energy reserves are sufficient. Low leptin signals that you need to build up your fat stores, and your brain orchestrates a response—“I’m hungry!”—to compel you to regain weight, even if that’s the last thing your conscious mind wants as you endeavor to maintain post-diet weight losses+ .
Or consider a study that will likely come out later this year. Eric Ravussin, PhD, a leading weight researcher at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, measured the contestants on TV’s The Biggest Loser and found their leptin levels to be in the tank (six had levels that didn’t even register on the standard measurement test)—which means the odds are their hunger pangs will be so intense that they’ll qualify for The Biggest Regainer in a few years. The physiological affront is actually a one-two punch. After significant weight loss, not only does our hunger increase but our metabolism slows, so we hold on that much more tightly to each calorie we consume. Researchers at Columbia University have found that people who, like those in the Melbourne study, lose at least 10 percent of total body weight burn 300 fewer calories a day on average than they did before the weight came off. (No one has looked at the metabolic effects of milder weight loss.) So at the same time that your brain is ordering you to eat more, you must eat less to maintain that slimmed-down physique. The woman who goes from 170 to 130 pounds through assiduous dieting and exercise may look just like her friend who’s always weighed 130—same shape, same percentage of body fat—but inside, her “fat brain” is still doing everything in its power to send her body back to Fatville. Hence the dirty not-so-little secret of weight loss: It’s not that hard to lose weight— motivated dieters do it all the time—but maintaining that loss is a bitch, with success rates as low as 2 percent or as “high” as 20 percent, depending on which studies you choose to believe.
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