For decades, medical experts have debated the weight-loss benefits and effect on health of high-protein diets. With the results of valid clinical tests of these diets now available, researchers, dietitians, nutritionists and doctors alike are reaffirming what critics of low-carb diets have said for years---they don't help adherents lose more weight than other diets, and they pose a variety of health risks.
They Don't Work
If the goal of a diet is to help the dieter lose weight and keep it off, high-protein diets don't meet that criteria. Studies of patients on high-protein diets have found not only high dropout rates, but that after one year of following a high-protein diet, patients had no statistical increase in weight loss over patients on more traditional diets. In addition, much of the weight loss from high-protein diets comes from water loss and loss of muscle mass---not fat.
Heart and Cholesterol Problems
Many of the foods which fall under the umbrella of allowable high-protein diet foods (such as red meats, eggs and dairy products) have high levels of saturated fats and cholesterol. This puts dieters at higher risk for heart disease, hyperlipidemia and hypercholesterolemia. Additionally, the lack of carbohydrates and resultant nutrient loss contributes to both heart disease and cancer risk factors, according to medical experts such as Belinda Linden, head of medical information at the British Heart Foundation.
As carbohydrate intake decreases, kidneys must burn stored glycogen (the form in which the body stores carbohydrates). Glycogen contains significant amounts of water, which is released during this process, resulting in more urination. Since water weight is a significant part of the weight loss from a high-protein diet, this can lead to dehydration. This puts a strain on the kidneys, affecting their ability to absorb calcium. These strains on the kidneys can cause a permanent, complete loss of kidney function in persons who have impaired kidney function to begin with, according to a study by Harvard University.
The lack of carbohydrates in high-protein diets robs the body of many important vitamins and minerals. Of particular concern to medical experts is the loss of calcium, due to both the decrease in the kidneys' ability to absorb calcium and the process of ketosis (a rise in blood acid levels when more fat is burned due to a lack of carbohydrates), which can lead to a loss of minerals such as calcium, in bones.