Those hoping to lose weight this year might be tempted to try a diet challenge in the hopes of kick-starting their weight loss. But while we might think these kinds of short-term, restrictive diets will help give our waistlines a nudge, psychology and physiology show us why this strategy can be so hard to stick to – and why it probably won't result in long-term weight loss. Research estimates that as few as 20 percent of people who lose weight through dieting manage to keep the weight off long-