This seems to be the hottest topic on low carb and keto forums around the world: is the old paradigm of “a calorie is a calorie” still valid or you can eat all the fat that you want and still lose weight if you stay under 25 grams of carbs per day?

Please, bear with me, this is a topic that can’t have a short answer.

How are calories measured?
Calories in the macro nutrients of food are measured in a lab, practically burning the carbs, fats or proteins and measuring the heat generated. It’s a bit like in your fireplace, where a pine log will produce less heat that a similar chunk or redgum. But exactly like different woods burning in your fireplace, different nutrients are absorbed in a different way in the body: pine is burning quick and fast, it makes a nice flame but doesn’t really heat much, while redgum is burning slow and low, for a long time.

OK, but we aren’t a fireplace.
Of course we aren’t like a fireplace, neither we are like a calorimeter (the instruments used to measure calories). Actually a calorimeter is pretty much a fireplace, but we are not.

Our body needs calories to process food
Breaking down food and processing its components takes energy, that means that we need calories to digest the food that we eat, and some foods take more energy than other.

Protein for example takes more calories to digest that fat or carbs, so much that on a research ( showed how in healthy young women the amount of energy required to digest a high protein meal was twice as much than a low fat, high carb meal. Twice as much.

But that’s not all.

In another research the energy spent digesting the food was measured for both lean and obese adults, and the result was that a high protein meal “cost” almost three times the energy of metabolizing a high fat meal.

So, a calorie isn’t a calorie.

Of course it isn’t, and it doesn’t take a scientist to prove it: try eating 1000 calories of sugar and 200 calorie of protein a day for a week and compare the result with eating 1000 calories of fat and 200 calories of protein a day for another week. Here is the link to a research that’s done exactly that.

Guess what, the result won’t be the same!

That’s why counting calories is an ineffective way of losing weight, and it’s often linked to losing the wrong weight: you want to lose fat, not muscle, possible intravisceral fat that’s the one linked with higher all causes mortality.

OK, a calorie isn’t a calorie, that means I can eat all the butter I want?
Well, it depends. Do you think a 65 years old sedentary obese woman can eat the same as a 18 years old athlete? Probably not.

Let’s try to be as clear as possible:

1. If you are losing weight eating a lot of fat, continue to do that;
2. If you want to lose weight but you are stalling for less than a few weeks, don’t change anything and wait;
3. if you want to lose weight but you are stalling for more than a few weeks, eat less fat
4. if you don’t want to lose weight, eat fat to satiety, it’s very unlikely that you could overeat and start getting fatter; if that happens, reduce your fat intake.

It’s that simple, folks.

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