Until a couple of years ago I'd always believed that "a calorie is a calorie," that it didn't matter whether I ate steamed vegetables or Halloween candy all day, as long as I didn't eat more calories than I burned.
But that idea has been turned on its head recently, as a growing chorus of experts have spoken out about the link between insulin and diet success. They say that when we consume food and drink that cause our insulin levels to spike, we set off a metabolic process that makes us (and keeps us) fat. According to this school of thought, calories are not created equal, and a low-carb diet will lead to more weight loss than a high-carb one, even if the number of calories consumed is the same.
A recent small study published in the Journal of the American Medical Association supports this idea. Researchers studied a group of 21 young adults who had already achieved 10-15% weight loss, then put each subject on a series of three weight maintenance diets for four weeks each—a low fat/high carb diet, a low-glycemic index diet and a very low-carb diet, testing their energy expenditure and hormone levels along the way.
They found that the low-carb diet resulted in the most energy expenditure and metabolic indicators most likely to promote maintaining the weight loss—in other words, a low-carb diet equaled a "faster metabolism" than a high-carb/low-fat one.
Although the study authors don't speculate as to why low-carb won the competition, the Los Angeles Times quotes Dr. Robert Lustig as saying, "To borrow a phrase from Bill Clinton: It's the insulin, stupid." According to Lustig, insulin and diet success are connected because the less insulin is released into the blood, the more efficiently the body burns fuel and the less tired and hungry we feel. Lustig is the UCSF Pediatrics professor who is on a crusade against sugar consumption and has suggested that sugar should be regulated or taxed by the government. I heard him speak last year and he reasoned that the government doesn't regulate things that are habit-forming but not harmful (coffee for example) and doesn't regulate things that are potentially harmful but not habit-forming (OTC pain killers, for example) but does regulate things that are both habit-forming and harmful—cigarettes and alcohol being the two big examples. Lustig reasons that sugar falls into that last category, so the government should save us from ourselves with greater taxation or oversight of some kind.
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