"If you eat 2,700 calories per day, that's roughly 1 million per year, 10 million in a decade. ~12 tons of food in a decade. To maintain your bodyweight to within 5lbs in a decade would require an accuracy of 0.1% in your calorie counting. Under this model, the question isn't why do people get fat, it's how does anyone avoid it?" - Gary Taube's Big Fat Lies lecture.