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A high protein plan is a diet plan that emphasizes protein-rich foods, such as meats, poultry, seafood, and protein-rich vegetables and grains, such as quinoa and legumes. Diets high in protein also tend to be reduced in either carbohydrates or fats. Extreme forms of this diet often emphasize a simultaneous low-carb and low-fat approach.
Most popular high protein plan diets focus on carbohydrate and sugar restriction to some extent, emphasizing the importance of regulating blood sugar and insulin levels. These diets purport to work by lowering chronically elevated blood sugar and insulin levels, thereby encouraging the body to burn fat for fuel instead of storing it in the fat tissue. When insulin levels drop, fat stored in the form of triglycerides typically breaks down into a smaller kind of fat called free fatty acids, which exit the adipose tissue and enter the bloodstream to be burned for fuel. Low carbohydrate diets that contain ample amounts of protein and fat have been clinically shown to satiate better than traditional low-fat diets. They also may provide health benefits, such as reduced risk for developing many diseases, including Alzheimer's, type 2 diabetes, and cancer.
A high protein plan may not be advisable for every dieter, however. Too much protein in the diet, particularly when taken without adequate dietary fat from animal sources, can cause kidney and liver problems in certain predisposed individuals. Excessive protein consumption can also drive a small but potentially significant insulin reaction. That being said, most mainstream high protein plan diets provide the essential vitamins and nutrients the body needs. On a severely carbohydrate restricted diet, the body typically breaks down amino acids from proteins into sugar via a process called gluconeogenesis. A low carbohydrate diet also may cause the body to produce an energy source called ketone bodies, which can be utilized in place of glucose for fuel.
Dietitians and obesity scientists often justify the high protein plan by citing evidence from evolution. In the Paleolithic Era, from approximately 2,000,000 years ago to 10,000 years ago, our human ancestors lived as hunter-gatherers. According to most anthropological data, these hunter-gatherers ate primarily meat along with some spare amount of fruits, vegetables, nuts, and seeds. They did not consume sugar and refined carbohydrates, since they lacked the technology to produce these foods in any kind of abundance. Thus, a high protein plan low in carbohydrates appears to be more in line with what human beings evolved to consume.