The food-exercise equation

Exercise, ironically, is being singled out by some as a deterrent to weight-loss efforts.

"There's this hunger issue," says Kendrin Sonneville, RD, a researcher at the Harvard School of Public Health. Her study about how kids who exercised the most ate back all the calories they burned off, and then more, was featured in a Time cover story, "Why Exercise Won't Make You Thin," last year. The food-exercise equation is imbalanced. It may take an hour to burn five hundred calories but only five minutes to eat them back."

And that's exactly what your body wants you to do. "In the short term, during or right after a workout, exercise may suppress hunger," says Barry Braun, PhD, professor of kinesiology and director of the Energy Metabolism Laboratory at the University of Massachusetts in Amherst. "But later that day, your hunger hormones can surge, making you want to eat. At the same time, your body's satiety hormones (the ones that signal that you're full) may decrease." 

The really unfair part, Braun notes, is that the desire to eat more after exercising hits women harder than men. "When we look at blood samples of people starting an exercise programme, there is a subtle change in men's hormone levels, but for women, exercise really elevates the hormone that increases appetite," he says. "The widely accepted theory is that women's bodies are hardwired to hold onto energy for reproduction purposes." So when your body senses that you're burning fuel from exercise, it wants to be sure you replace it as soon as possible.

All of which means that for women who love fitness and want to be toned as well as trim, shedding kilograms poses a unique challenge. But the payoff is well worth it: "What all the latest news stories missed is the role exercise plays in keeping the kilograms off in the long run," says Timothy Church, MD, PhD, a professor at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, who has done extensive research on the factors that influence successful weight loss. "It's a fact that the only people who keep off the weight they've lost are the ones who are physically active." Studies show that those who use dieting alone to drop kilos usually find themselves right back where they started or even heavier. 

 

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