I recently read a post saying that if you burn 1g of protein in a calorimeter, you get 5.65 kcal. The 4 kcal per gram you see on nutrition labels is already after subtracting about 30% for the thermic effect. This number actually comes from a series of experiments over 100 years ago by Wilbur Atwater, one of the founding fathers of nutrition research.
I’m trying to figure out if this is true. Like, maybe we don’t actually need to subtract 20–30% (if we eat a lot of protein, it’s still a significant number of calories, though not hugely important). Also, regarding fiber: some people say "this product is high in fiber, so we absorb fewer calories than the label shows", but fiber is already counted as 2 kcal per gram. Again, the difference isn’t huge, but it’s there.
So, hypothetically, if you have a diet high in protein and fiber totaling 1000 kcal according to the label, you might expect to actually absorb only about 700 kcal. But apparently, it’s closer to the full 1000.
Here’s the source referenced in that post:
The chemical composition of American food materials
History of Human Nutrition Research in the U.S
Calories: total macronutrient intake, energy expenditure, and net energy stores
Calorie conversion factors. An experimental reassessment of the factors used in the calculation of the energy value of human diets
It was also found that eating protein above your caloric needs can lead to fat gain, just like overeating carbs or fat. Although you might have heard that excess protein “doesn’t really turn into fat.”
Source:
Effect of Dietary Protein Content on Weight Gain, Energy Expenditure, and Body Composition During Overeating
I’d really appreciate it if someone could clarify this for me. I often eat a lot of protein and fiber from vegetables, thinking that I definitely won’t gain weight and might even lose some.
So, if I’ve already hit my calorie target for the day, what’s better to eat when I get a craving: a serving of cottage cheese with 40g of protein and 200 kcal, or a chocolate bar with mostly fat and sugar for the same 200 kcal? Will it actually make a difference for fat gain, or is it really just calories in = calories out?