A high protein diet is one that consists of more that 30% of the daily caloric total from protein, or 3 times the protein RDA for athletes. When a person eats a higher percentage of protein, their kidneys are overworked. They are also increasing their intake of saturated fat & decreasing the amount of fiber as well. Both of these instances increase the risk of heart disease and cancer.
Consuming a high amount of protein causes the body to go into ketosis. Ketosis changes the pH balance of the blood. There's less oxygen. The decrease in oxygen promotes an environment in the body that helps cancer grow. The body tries to balance the pH balance of the blood by taking calcium to neutralize the effects.
For every gram of protein consumed above tissue maintenance, between 1 and 1.5 mg of calcium is excreted. The typical American diet already consumes very little calcium. By depleting calcium stores in the body, people who eat high protein diets are at a higher risk for osteoporosis. Especially women.
The need for fluids is also increased by high protein intake. Protein requires approximately seven times the water for metabolism than carbohydrates or fat. The low carb consumption (common for weight loss) can lead to a decrease in glycogen stores (energy) which results in poor physical performance and dehydration.
So overall, high protein diets increase your risk of heart disease, cancer and osteoporosis. It causes your kidneys to overwork, your body is prone to dehydration and as a result, you will have very little energy. It's not really the picture of health, is it!