Foods high in pro­tein are tout­ed as the best foods for weight loss. But eat­ing more pro­tein does­n’t mean you can eat pro­tein foods with­out count­ing the calo­ries in them. Where do excess calo­ries from pro­tein go — to fat or some­where else?

It’s nice to think that you can only eat pro­tein and nev­er gain weight. Sci­ence has some data on this mat­ter.

Eat­ing too much pro­tein can turn into fat and increase your weight, but it’s not as easy on your body as turn­ing carbs or fat into fat tis­sue.

Can protein make you fat?

The body turns excess glu­cose into fat if you don’t need it for ener­gy. The fact is that pro­tein is not usu­al­ly con­vert­ed into glu­cose; your body “prefers” car­bo­hy­drates and fats for these pur­pos­es because they are the eas­i­est to con­vert into calo­ries.

Do you need protein for energy?

Pro­tein, of course, car­ries ener­gy in the form of 4 kcal. But the body uses pro­tein as ener­gy last. First of all, pro­tein is a build­ing mate­r­i­al for cells; enzymes are formed from it, which con­trol many process­es in our body.

How does protein intake affect body weight?

Many stud­ies note that even with severe overeat­ing of pro­tein, adi­pose tis­sue remains vir­tu­al­ly unchanged.

A 2016 study pub­lished in the Jour­nal of Nutri­tion and Metab­o­lism found that when healthy, trained men con­sumed 3.3 grams of pro­tein per kilo­gram of body weight per day (g/kg/day) for four months, they did not gain fat com­pared to those who fol­lowed a tra­di­tion­al healthy diet. (How­ev­er, they did not have any changes in blood lipids or liv­er and kid­ney func­tion).

Anoth­er wide­ly cit­ed study in the Jour­nal of the Inter­na­tion­al Soci­ety of Sports Nutri­tion found that when healthy, trained men increased their pro­tein intake to 4.4 g/kg/day—five and a half times the rec­om­mend­ed dai­ly value—their body fat did not increase at all over the course of two months.
But what if you’re some­one who does­n’t exer­cise much and you’re overeat­ing on pro­tein?

The ques­tion aris­es: if excess pro­tein does not turn into fat, then where does it go? Addi­tion­al amino acids must find their use.

Where does excess protein in the body go?

Pro­tein is first bro­ken down into amino acids in the stom­ach and intestines. They are trans­port­ed through the blood­stream to the liv­er and oth­er organs and tis­sues, where they are used as func­tion­al units.
But the body can­not store amino acids. So if you eat more than you need to cre­ate func­tion­al pro­teins, they will be con­vert­ed into glu­cose
in the form of glyco­gen or, as a last resort, for ener­gy.
Glu­cose can also be con­vert­ed to triglyc­erides and stored as fat. Some amino acids are keto­genic (such as leucine and lysine) and are pref­er­en­tial­ly con­vert­ed into ketones, an alter­na­tive source of ener­gy.
Thus, amino acids from excess dietary pro­tein can be con­vert­ed into:

  • Urea, which is excret­ed in urine.
  • Glu­cose, which is used for ener­gy and stored as glyco­gen.
  • Fat (excess glu­cose is con­vert­ed to triglyc­erides and stored as fat).
  • Ketones (alter­na­tive ener­gy source) from keto­genic amino acids.
  • Ener­gy obtained direct­ly from amino acids.

How­ev­er, using pro­tein for ener­gy isn’t the eas­i­est, so the body only uses it as a last resort when there aren’t enough car­bo­hy­drates or fats (or you’re eat­ing much more pro­tein than you need in amino acids).

Fat accumulation from protein

The­o­ret­i­cal­ly pos­si­ble, but unlike­ly. Increas­ing your pro­tein intake is gen­er­al­ly asso­ci­at­ed with high­er sati­ety, weight loss, and fat loss over time. But of course, this depends on what you eat and the type and amount of phys­i­cal activ­i­ty. Addi­tion­al­ly, many high pro­tein foods con­tain more than just pro­tein.

Eat­ing a lot of pro­tein can also mean you’re like­ly to eat more fat and car­bo­hy­drates, espe­cial­ly if you love cheese or meat. How­ev­er, eat­ing more pro­tein usu­al­ly results in eat­ing few­er calo­ries because pro­tein has a high­er sati­ety index than fats or car­bo­hy­drates.

Many peo­ple find it dif­fi­cult to eat large amounts of pro­tein, but if you want to snack on some­thing, choose pro­tein options. They are high­ly like­ly to not affect your waist­line.