A stress-free life is unfortunately just a fairy tale. Also unfortunate is the fact that chronic stress can lead to weight gain. This happens for a variety of reasons, one being that stress makes you hungry.
As we evolved, stressful situations required great physical energy, like running from a saber-toothed tiger. Then and now, a stressful situation triggers a shot of adrenaline followed by a surge of cortisol, which signals your body to replenish the calories you used. However, editing the last few PowerPoint slides before your big presentation doesn't burn nearly as many calories as sprinting away from a dangerous man-eating animal. In stressful moments, we often tend to reach for foods high in sugar and fat that prompt the brain to release pleasure chemicals. If your stress is chronic, this high-calorie food response can become habitual, leading to pounds gained.
For the second and more physical reason stress causes weight gain, read more.
The production of cortisol interferes with the production of testosterone, the hormone responsible for building and maintaining muscle mass. A decrease in muscle mass leads to a slower metabolism, since a pound of muscle requires more energy (read: calories) to maintain than a pound of body fat. The good news is that exercise combats stress. Movement tricks your body into believing that you're really running away from that scary tiger. Exercise gets the blood flowing, which helps flush the cortisol from your body. Studies have shown that walking just under 20 minutes, three times a week can lower cortisol levels by 13 percent. Now doesn't a lunchtime stroll sound appealing?