High Protein or a high-protein diet is often recommended by bodybuilders and nutritionists to help efforts to build muscle and lose fat. It should not be confused with low-carbohydrate diets, such as the Atkins Diet, which are not food-energy–controlled and which often contain large amounts of fat.

While adequate protein is required for building skeletal muscle and other tissues, there is ongoing debate regarding the use and necessity of high-protein diets in anaerobic exercise, in particular for weight training and bodybuilding.

Extreme protein intake (in excess of 200 g per day), coupled with inadequate intake of other calorie sources (fat or carbohydrates), can cause a form of metabolic disturbance and death commonly known as rabbit starvation. Even when consuming other calorie sources, consuming more than 285 g of protein per day (for an 80 kg person) may be unsafe.

Relatively little evidence has been gathered regarding the effect of more moderate long-term high intake of protein on the development of chronic diseases. Increased load on the kidney is a result of an increase in reabsorption of NaCl. This causes a decrease in the sensitivity of tubuloglomerular feedback, which, in turn, results in an increased glomerular filtration rate. This increases pressure in glomerular capillaries. When added to any additional renal disease, it may cause permanent kidney damage.

As is apparent from the list below, many high-protein foods (indeed, most low-carb foods with protein) are fairly low in fiber. This can lead to discomfort if additional roughage is not added to the diet. A 2017 review paper in the New England Journal of Medicine suggests that high protein diet may contribute to life-long risk of kidney damage including chronic kidney disease.