Why All Calories Are Not Created Equal
Of all the nutrition myths, the calorie myth is one of the most pervasive and most damaging.
It's the idea that the amount of calories are the most important part of the diet and that the sources of these calories don't matter.
The human body is a highly complex biochemical system with elaborate processes that regulate energy balance. Different foods go through different biochemical pathways, some of which are inefficient and cause energy (calories) to be lost as heat.
Even more important is the fact that different foods and macronutrients have a major effect on the hormones and brain centers that control hunger and eating behavior.
One aspect of this calorie inequality is the thermic effect of food.
The Thermic Effect of Food
Different foods go through different metabolic pathways. Some of these pathways are more efficient than others, so for some foods more of the food's energy, that is "calories", are burnt up just in the process of metabolising that food.
The metabolic pathways for protein are less efficient than the metabolic pathways for carbs and fat, so while that sound like a negative, what it actually means is that it takes more energy to reach it's final destination.
Protein contains 4 calories per gram, but a large part of these protein calories is lost as heat when it's metabolised by the body.
The thermic effect of food is a measure of how much different foods increase energy expenditure, due to the energy required to digest, absorb and metabolise the nutrients.
Here is the thermic effect of the different macronutrients:
- Fat: 2 - 3%
- Carbs: 6 - 8%
- Protein: 25 - 30%
If you go with a thermic effect of 25% for protein and 2% for fat, this would mean that 100 calories of protein would end up as 75 calories, while 100 calories of fat would end up as 98 calories.
Studies show that high-protein diets boost metabolism by 80-100 calories per day, compared to lower-protein diets.
Put simply, high-protein diets have a metabolic advantage!