From The First 20 Minutes: Exercise Better, Train Smarter, Live Longer by Gretchen Reynolds.
Meanwhile, despite the popular notion that slow exercise burns more fat than longer, harder bouts, it doesn't.
Did people burn more fat calories in the hours after they'd exercise? The answer was an unequivocal no.
Why exercise doesn't inevitably make people skinny is one of the more intriguing and vexing issues in physiology. Yet study after study finds that, with some rare exceptions, it does not..."In general, exercise by itself is pretty useless for weight loss," says Eric Ravussin, Ph.D., a professor at the Pennington Biomedical Research Center and an expert on the topic.
The idea that you can walk your way to fitness, it's just not proving to be true.
In physiological terms, the results are "consistent with the paradigm that mechanisms to maintain body fat are more effective in women," Dr. Braun and his colleagues wrote. In practical terms, they're scientific proof that life is unfair. Female bodies, inspired almost certainly "by a biological need to maintain energy stores for reproduction," Dr. Braun says, fight hard to hold on to every molecule of fat. Exercise for many women (and some men) inexorably increases the desire to eat.
Several years ago, researchers discovered that people who carry certain variations of a gene known as the fat-mass and obesity-associated, or FTO, gene have an enormously increased risk of becoming obese over their lifetimes. Close to a third of Americans of European descent may harbor this gene.
Other scientists have found that physical fitness, whether or not it's accompanied by personal fatness, leads to a longer, more robust life.
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