However, most diets are rigid and unsustainable. On average, weight loss attempts last four weeks for women and six weeks for men. You may be able to relate to this (i.e., following a strict diet plan for a few weeks, but then going back to your old eating habits, with the weight soon returning).

What causes diets to fail?

Changes in gene expression may help explain why so many diets fail. Dieting increases stress sensitivity, and stress makes us seek out rewarding things like high-fat, high-calorie "comfort" foods. "Dieting is tough because your brain is working against you," Bale says.

How often do diets fail?

Dieting is often synonymous with suffering, so consider the reverse: 95 percent of diets fail people.