The protein in our food supplies amino acids that we need for replacing proteins lost in urine, in shed hair and skin, and through other means. Because we can't store protein for the long-term, we need to eat some every day especially the 9 "indispensible" (or essential) amino acids that our cells cannot make from other nutrients.
The amount of protein we need to eat to replace what we lose is relatively modest. A generous estimate is 10% of our daily calories, which amounts to 56 grams per day for the average man and 46 grams for the average woman. Any protein we eat beyond what we need for rebuilding is burned for energy, converted to sugar, or most commonly converted to fat.
While some of the protein from our food becomes protein in our bodies, eating a high-protein diet will not necessarily help the body build more muscle protein. Mostly it just builds fat.
A number of diets recommend eating high amounts of protein, and some evidence suggests that for people trying to lose weight a high-protein diet reduces hunger and food cravings. According to the Institute of Medicine, we can get up to 35% of our calories from protein and suffer no ill health effects. But regardless of what we eat, weight loss will only occur when we burn more calories than we consume. When a high-protein diet contains more calories than we need, the excess still builds up as fat.
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Sugars consumed in excess are also readily converted to fat for storage. To learn more, visit Spotlight on Sugar.
The protein from our food doesn't necessarily become protein in our bodies. Our cells can burn amino acids as fuel and convert them into sugar and fat.
