Severely restricting carbohydrates is not the reason some people experience weight loss with a high-protein diet. It's the protein that sates their appetite and helps them lose weight. In a study, people who ate just a bit more protein each day, while eating less fat and an average amount of carbs, felt sated earlier, ate fewer calories, and still lost weight.

Some high-protein diets ask people to eat three times as much protein as they do carbohydrates and limit their carbs to as little as 50 grams per day or less. Severely limiting carbohydrate intake and getting most of your calories from protein can be unhealthy for several reasons. First, many healthful foods are high in carbohydrate, including whole grains, legumes, fruits, and vegetables. A diet that severely restricts carbs will lack these nutritious foods. Second, a diet that is extremely high in protein can cause ketosis, a physiological state that can lead to gout or increase the risk of kidney or liver problems or electrolyte imbalances. For optimum health and weight loss, eat a healthy, well-balanced diet consisting of foods from all major food groups. In a recent study, researchers compared the effects of diets containing different amounts of calories from protein, fat, and carbohydrates. When participants followed a calorie-controlled diet consisting of 30 percent of calories from protein, 20 percent from fat, and 50 percent from carbohydrates, they felt much more satiated than when they consumed a diet with less protein, more fat, and the same amount of carbohydrates. Later, when they were allowed to consume as many calories as they wanted as long as they stuck to the 30:20:50 ratio, participants consumed about 450 fewer calories per day and lost almost 11 pounds.