Weight and fat are national obsessions because more than two-thirds of Americans are overweight or obese. Most people have misperceptions about weight gain. Common beliefs include low metabolism, high digestion of food, damaged metabolism due to chronic dieting, eating one or two large meals per day instead of many small meals, and consuming too many carbs.
All of these are urban legends and are not true. Claude Bouchard from the Pennington Biomedical Research Center in Louisiana has identified five factors linked to weight gain (New Scientist, November 15, 2014):
1.Low muscle mass, which reduces metabolic rate
2.Low fitness, which decreases the capacity to expend calories through physical activity
3.Low testosterone, which is linked to the capacity to build muscle
4.Insensitivity to the hormone leptin, which helps control appetite and metabolic rate 5.Inability to directly burn dietary fat as fuel, which results in greater fat storage.
No single factor is responsible for weight gain. The complexity of body fat control helps explain why it is so difficult to lose weight and keep it off.