[eli5] Why does 1g of protein give 4 calories, while protein is used in muscle building, so if not taken beyond limit, all protein would be used in muscle building and not respiration to give off energy?

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Okay so this assumes that calories are basically energy from respiration, if im wrong please correct me as well, i know that a calorie is considered the energy to heat up 1g of water i think or something, but generally its energy , and the body currency of energy is ATP which is mainly from respiration right, so amino acids from protein are usually not used in respiration unless taken beyond a limit, but that isn’t taken into account when calculating its calories, every 1g of protein gives off 4 calories same amount as carbs, which is the main source of fuel for respiration lol, is there something i misunderstood about calorie concepts?

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Anonymous 0 Comments

You’re thinking back to front. Your body doesn’t save up the protein for muscles – first it meets its calorie needs.

So, if you eat nothing for days and then eat a steak, most of that protein will be used for energy.

If instead you ate an ice cream, a buttered potato and a steak, your body prefers to use the carbs and fat for energy before breaking down the protein.

If you have protein left over after you’ve met your most basic energy needs, then you’ve got protein for muscle building.

Also, you’re thinking about it a little too literally. Your body is not a perfect machine. It doesn’t perfectly convert food to energy and other purposes.

Things in your body happen almost by chance. If your brain decides your body needs some protein for muscle repair, then it will make more of the molecules which connect with the right amino acids to make those proteins. But meanwhile, your body is also making the molecules that match with protein to make energy. They’re competing with each other. So the food you eat isn’t perfectly converted to one or the other, your body can only shift the odds that the proteins will meet the muscle repair molecules rather than the energy converter molecules.

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