Q: I’ve heard that dietary fat is more fattening than calories from carbs or protein. Is this true?
– Scott in Detroit
A: Yes and no. One study from Vanderbilt University found that if you overeat fatty foods, you store up to 95% of the excess as body fat, while the equivalent in excess carbs results in a slightly lower fat conversion, or 85% of the extra calories. Dietary fat is more readily stored as body fat, if only because the body must work harder to convert carbohydrates and protein to fat, while dietary fat can be stored as is. That increased work equates to a slight loss of calories. “Excess” is the key word here. There is no evidence that dietary fat is stored in any greater amount than carbs or protein if you are balancing calories in with calories out. It is overeating that gets us into trouble, and it is much easier to overeat fat, since it is such a concentrated source of calories. A wealth of research shows that high-fat diets are the ones most likely to pack on the pounds, primarily because they are so calorie-dense. In contrast, foods rich in fiber and water – from smoothies, tomato juice, and fruit to soups, stews, veggies, and whole grain cereals soaked in milk – fill us up on few calories and are the best waist-synchers around. (Carb-rich foods also appear to rev the metabolism more than fat, while the metabolic rate slows a tad when carbs are eliminated from a weight-loss diet.) – Elizabeth Somer