Nutrition Mythbusters, Negative Calorie Foods?
Myth: Eating lots of negative calorie foods will help melt away the pounds!
Truth: Does celery, cucumber, lettuce, or grapefruit help you lose weight? Maybe, but not for the reason you might think. Touted as “negative calorie foods”—that is, foods that are so low in calories that it takes more energy to chew and digest them than the food contains. But is it true? Can you burn calories just by eating a lot of celery?
To answer that, let’s review how our metabolism works.In short, basal metabolic rate (BMR) is the number of calories your body burns at rest. Calculating BMR takes into account a person’s height, weight, and age. To figure out the total number of calories, multiply your BMR by an activity factor (1.2 for those who are sedentary, up to 1.9 for those who are very active).
It is true that our bodies expend some energy chewing, digesting, and absorbing what we eat. This is called the thermic effect of food. Compared with our BMR and our activity, however, the thermic effect of food has little effect on the calories we use, only about 5 to 15%. After you eat, there is a slight increase in calories burned. However, even with very low-calorie foods, this is unlikely to result in any significant weight loss.
Fruits and vegetables, which high in water content, low in calories, and high in fiber do aid in weight loss, but not because they have “negative calories.” Instead, they help you reach your weight loss goals by keeping you full longer and also help displace less healthy foods in the diet.