According to the June 2010 issue of Firtness Rx magazine:

High-protein diets are popular for weight loss and weight maintenance. These diets are often high in fats, so many nutritionists fear adverse health effects and poor weight maintenance.

A study from Masstricht University in the Netherlands showed that diets low in fat and hgih in either casein or whey protein were more effective for long-term weight control than low-fat, high-carbohydrate diets. The high-protein diets had no negative effects on risk factors for heart attack, stroke, or diabetes, such as cholesterol, LDL (bad cholesterol), insulin, HbA1c (measure of sugar metabolism), or leptin (controls appetite and metabolic rate). The high-protein diet group consumed two supplements per day of either 25 grams of casein or whey protein. (International Journal of Obesity, 33: 296-304, 2009)