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Comment by phil248 | Hacker News Reader

Carbs are great if you're actually going to use the energy! The best even! The problem with Western habits is we tend to carb load until we have a tremendous excess of energy which we then use to... sit down for several hours while our body gets busy turning all that unused energy in to fat.

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Converting carbs into fat is fairly inefficient. It comes at about a 40% calorie loss. So you can put on fat eating carbs alone but it’s not easy. More often than not we eat carbs together with fat so your body will very happily just directly store the fat and burn the carbs for energy.

This is why things like french fries or pizza are so fattening.

But if you eat just proteins and fat, the fat is not stored (see e.g. keto diet)

How can this be explained?

Yes it is:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5326984/

There’s no magic in keto. People lose weight on keto because they wind up eating fewer calories, usually because they cut back on processed junk food as part of going keto.

When you eat fat and carbs, the fat is stored and the carbs used for energy. When you subtract carbs, your body still needs energy so it starts using fat.

I’d guess it’s because in that case you don’t produce much insulin which is starting to be called the fat storage hormone.

Protein also stimulates insulin release. You’ll get a bigger spike of insulin from eating a steak than a plate of spaghetti.

Exactly. Humans are meant to move, and not moving makes us fat. Now that we're extremely sedentary, we literally have no use for the amounts of rice and pasta we consume. We're victims of our own success.

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