Q: A “negative-calorie diet” seems too good to be true. Is it?
A: A negative-calorie diet causes you to expend more calories chewing, digesting and absorbing certain foods than the food actually contains. As an example, proponents of this diet claim that if you eat a cup of chopped lettuce that has 10 calories, you’ll burn that off and then some! While this sounds great, I haven’t found any research validating this theory. The “thermic effect of food” refers to the energy spent processing food in our system for storage and use, but we do not yet have the metabolic tools to determine this value for single food items.
Other purported negative-calorie foods include celery, carrots, cucumber, onion, spinach, apple, cranberry, orange, peach, strawberry and watermelon. The eBook The Negative Calorie Diet states that you can lose up to 14 pounds in two weeks by eating these foods! At that drastic rate, it must mean that you can only eat these foods and nothing else. But, a prolonged diet of only fruits and vegetables lacks several key nutrients, including protein and essential fats. Weight loss should always be gradual (1-2 pounds per week) and accomplished by exercising and eating smaller portions of well-balanced meals, including several daily servings of fruits and vegetables. Weight management is a delicate balance between calories in and calories out. The foods deemed “negative-calorie” are nutritious, low-energy fibrous fruits and veggies that fill you up and leave less room for higher-calorie items. If including these foods in your diet induces any weight loss, it’s likely only due to the fact that you’re eating fewer calories in general, not because your body’s digestive tract is working overtime.