On the negative side, says Brehm, "restriction of carbohydrates may lead to inadequate intake of fiber, vitamins, and minerals due to decreased intake of grain, fruit, vegetable, and dairy groups. Also, high intake of protein may lead to stress on the kidneys."

Power Protein Pros an Cons

"In addition to weight loss and improvement in cardiovascular risk factors, the benefits of high- protein, low-carbohydrate diets include less hunger, which leads to fewer calories," says dietitian Bonnie J. Brehm, PhD, professor in the college of nursing at the University of Cincinnati, Ohio. “This diet also helps preserve lean body mass.