Let’s explore why you should be paying more attention to the types of food consumed instead of that little number on the back of a nutrition label.
Are All Calories Created Equal?
The first law of thermodynamics (or the law of conservation of energy) states that energy cannot be created or destroyed. When applied to weight control, this law translates to the basic formula:
weight gain = energy (calories) in – energy (calories) out
This traditional viewpoint argues that the food eaten is unimportant–a calorie is a calorie. To lose weight, create a calorie deficit by either eating less or burning more. To gain weight, increase calorie intake.
The opposing viewpoint maintains that calories still count, but the type of food consumed has a trickle-down effect on the amount of energy expended, and what foods the body craves. It takes way more energy to process and store protein than it does carbohydrate or fat–this is called the thermic effect of food. Essentially, one burns more energy dieting protein because it requires more energy for the body to process. In one study, twice as much energy was expended after meals on a high-protein diet versus a high carbohydrate, low-fat diet.1
Another study compared the effects of three diets differing in macronutrient (carb, fat, protein) composition on energy expenditure during weight loss maintenance. Weight loss causes resting energy expenditure (metabolic rate) to go down, which predisposes to weight regain. Results of the study showed that the very low-carb (and highest protein) diet had the LEAST effect on reducing resting energy expenditure following weight loss.2
The loss of energy as heat through the thermic effect of food is consistent with the second law of thermodynamics, which states that some energy is always lost in any chemical reaction. The idea that “a calorie is a calorie” defies this law.3