Why do so many of us get so fat? the answer appears obvious. “The fundamental cause of obesity and overweight,” the World Health Organization says, “is an energy imbalance between calories consumed and calories expended.” Put simply, we either eat too much or are too sedentary, or both. By this logic, any excess of calories whether from protein, carbohydrate or fat (the three main components, or “macronutrients,” in food) will inevitably pack on the pounds. So the solution is also obvious: eat less, exercise more.
The reason to question this conventional thinking is equally self-evident. The eat less/move more prescription has been widely disseminated for 40 years, and yet the prevalence of obesity, or the accumulation of unhealthy amounts of body fat, has climbed to unprecedented levels. Today more than a third of Americans are considered obese more than twice the proportion of 40 years ago. Worldwide, more than half a billion people are now obese.
Besides getting fatter, we are also developing more metabolic disorders, such as type 2 diabetes, which is marked by hormonal abnormalities in the processing and storage of nutrients and is far more common in obese individuals than in lean ones.