Excess protein in the diet combined with restricted carbohydrates can cause harm to the kidneys, dehydration, a decline in muscle mass and bone calcium, and create strain on the heart. Protein should account for 10 to a maximum of 35 percent of daily calories.
Excess protein in the diet can cause weight gain because the body only uses 50 grams of protein per day and stores the rest as fat. It can also adversely affect the brain, liver and nervous system by allowing toxins to build in the bloodstream. Animal protein also contains high amounts of cholesterol that can cause hardened arteries.