How does digestion work? Respectively, what part of food gets turned into ‘energy’ and what part is used as a building block?

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E.g. when eating a steak, there are proteins in it that one needs to build muscle. My question is, does all of that protein go towards building muscle, or does a part get turned into ‘energy’ or something else?

I’m asking as when I read the nutritional information of some protein powder, they had quite a massive amount of calories. There I realised that I actually have no clue how all these things relate to each other ><

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The fat, carbs, and proteins you eat slowly get broken down into smaller pieces starting in your mouth all the way to your intestines where most of the absorption of these nutrients happens. The amino acids you get from breaking down proteins can be used to generate energy, make hormones, build muscle fibers, and a bunch of other things.

Well, as with many things, the answer is complicated. The short answer is that essential amino acids are use as building blocks (these are the 9 amino acids your body can’t make itself) and the rest can be considered either energy or building blocks.

Let’s start by saying that proteins are large molecules made out of amino acids. So when we eat protein, we are eating a mixture of amino acids. Your body uses 20 different amino acids to make the proteins that are necessary to keep you alive, and of those 20 your body can make 11 of them on its own. The other 9 are the essential amino acids, because without eating them your body won’t function properly. So, it’s pretty obvious that when we eat those essential amino acids, many become incorporated into our bodies.

As far as the rest of what you eat goes, it ca me to be either thought of as building blocks or as energy. This is because those building blocks can be synthesized by your body, so depending on your levels at the time of the meal some will be used for energy, and others will be used as building blocks. It’s even possible one nonessential amino acid is used to make another one!

Hope this sheds some light on the process!

Each gram of protein only provides 4 calories of energy. If you see protein powder that exceeds this value, per gram, then all the extra calories are coming from something else they’re adding in the powder, likely other carbs/sugars.

Protein in your body is primarily used to repair tissues, including muscles, bones and skin, and produces necessary enzymes, and a few other functions.

For Energy needs, your body will usually first go for your Glycogen stores (Glucose, primarily from Carbs), then Fatty Acids. Then when needed, it could tap into proteins for energy.