In today’s United States, where food is abundant, affordable and irresistibly delicious, overweight and obesity are now an epidemic. And, as the epidemic keeps growing, weight loss and dieting have become major topics of conversations, media coverage and health care research. The secret to weight loss is simple: Consume fewer calories than the body uses. And any diet that limits caloric intake will do the trick. The problem is, when people go off the diet, they gain the weight right back. That happens because most diets require that we deprive ourselves of certain foods or food groups — and many can’t sustain this for long.