Calories from Proteins, Carbs, and Fats: Is There a Difference?
Regarding the first law of thermodynamics, a calorie is a calorie. That is, no matter what source it is from, one calorie is the energy required to increase the temperature of one kilogram of water by one degree Celsius. Energy can be neither created nor destroyed. It can only be transformed.
Here’s a little bit of historical science behind the accepted caloric value of protein, carb, and fat in the diet. The past work of Rubner and Atwater is the standard used today. Using a bomb calorimeter to measure the heat of combustion of various proteins, carbs, and fats, they determined the energy density of dietary protein = 4.1 calories/gram, carbs = 4.1 calories/gram, and fat = 9.3 calories. Rounded off, it is 4 calories/gram of protein, 4 calories/grams of carbs, and 9 calories/gram of fat that we currently use (and why many panic when they see fat is more than double in potency).
Past thinking was to eat .7 to 1.0 grams of protein per pound of body weight, load up on the carbs for energy, and minimize the fat. After all, 15 grams of fat has 135 calories and 15 grams of carbs has only 60, so to help shed the pounds, back off on the fat intake. But it’s not that simple. The type of protein, carb, and fat must be considered as well as how the body processes them.