Many of the popular weight loss diets are based on increasing protein content. A very recent and very well-controlled feeding study confirmed the effectiveness of increasing protein. Women were put on a standard energy restricted diet (1000 kcal/day) and then given extra calories (250 kcal/day) in the form of beef, chicken, or a combination of carbs and fat. There was greater weight loss in the two groups given extra protein in the form of either beef (-15 lbs) or chicken (-17 lbs), compared to the group given extra calories as carbohydrate and fat (-12 lbs). Thus, adding protein in the form of meat was beneficial for weight loss. Further, the type of meat, chicken or beef, did not matter in respect to the greater weight loss.

Mahon et al. Effect of protein intake and protein sources on energy-restriction-induced changes in body weight and body composition in overweight and mildly obese postmenopausal women. Federation of American Societies for Experimental Biology, Washington D.C., April, 2004. Abstract #583.6.