Purpose of review: High-protein diets, often with carbohydrate restriction, are quite popular among overweight Americans pursuing strategies for weight control. Recently, well designed clinical trials have evaluated the anthropometric and metabolic effects of these diets. This review focuses on the impact of high-protein diets on energy expenditure and satiety; the diets' effects on weight loss, body composition, cardiovascular risk, and glycemic control; and potential detrimental consequences of high-protein intake.
Recent findings: Current evidence indicates that protein-induced energy expenditure and satiety contribute to weight control. Randomized, controlled trials continue to show comparable, if not superior, effects of high-protein diets compared with lower protein diets on weight loss, preservation of lean body mass, and improvement in several cardiovascular risk factors for up to 12 months. Evidence that chronic high-protein intake affects glucose metabolism is inconclusive at present. Further study of the long-term safety of diets with varying amounts of protein is warranted.
Summary: On the basis of patients' metabolic profiles and preferences, practitioners can recommend individualized, nutrient-rich diets within current nutritional guidelines for weight control. Diets moderately increased in protein and modestly restricted in carbohydrate and fat, particularly saturated fat, may have beneficial effects on body weight, body composition, and associated metabolic parameters. Key issues must be resolved regarding the long-term compliance and safety of chronic high-protein intake.
Brehm BJ, D'Alessio DA, Benefits of high-protein weight loss diets: enough evidence for practice? Current Opinion in Endocrinology, diabetes and Obesity: October 2008 - Volume 15 - Issue 5 - p 416-421
This research study concludes that diets slightly higher in protein, compared to carbohydrate and fat intake, are beneficial for body weight and for a leaner body composition. Researchers found that protein induced and promoted energy expenditure and promoted feelings of fullness and satisfaction that contributed to weight control. Another recent study also found that increasing protein intake resulted in sustained weight loss, and helped to maintain a healthy weight .
Protein is the single most important nutrient that influences metabolic rate and weight loss. Every cell in the human body contains protein. It is a major component of skin, muscles, organs, and glands, and helps to improve immunity, antioxidant function, the production of enzymes, and enhances insulin function. Complete proteins are especially important because they form the structure and integrity of every part of the body.
Meat is the not the only source of high quality, complete protein
Meat and dairy products including poultry,eggs and fish all contain complete sources of protein, i.e. all essential amino acids that the body needs. However complete proteins can also be obtained from a vegetarian diet.
The amino acids found in vegetables are just as high quality as the amino acids found in animals products and can be used just as effectively by the human body. Most protein from vegetables usually contain most of the nine essential amino acids, but one or two of them may be at low levels compared to the protein in animal foods. There are a handful of vegetarian sources that offer complete protein and can stand alone as the main protein source in any meal. These include:
Foods that offer high levels of incomplete protein include beans, peas, nuts, seeds, and many grains. beans, lentils, and peas can be easily combined with brown rice or corn to create a delicious complete protein dish.
If you are trying to lose weight, go easy on high carbohydrate foods that are easily broken down in the body and can leave you feeling hungry again quickly, like pasta, potatoes, rice and bread. Eat foods that are good sources of protein and that provide a feeling a satiety, especially complete proteins, as often as possible.
 Weigle et al A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations. Am J Clin Nutr 2005, pages 41-8.