A Protein-Sparing Diet

A protein-sparing diet is a modified fast, intended for obese individuals to achieve rapid weight loss, the Cleveland Clinic says. It includes not only dietary components, but medical and behavioral aspects as well. The protein-sparing diet is very restrictive and should be a plan you follow while working with your physician and dietitian.

How the Diet Works

In an ideal world you would only lose fat tissue rather than lean body mass while dieting. Nevertheless, some loss of lean body mass occurs with any weight-loss diet, particularly with very low-calorie diets. Although a protein-sparing diet typically provides fewer than 900 calories per day, it avoids most loss of lean body mass because it includes 70 to 90 grams per day of high-quality protein, according to a 2006 issue of "The Journal of Nutrition."

The Process

Carbohydrates are usually the body's primary source of energy. When a person's diet severely limits carbohydrates, the body begins to burn fat as its primary fuel source, the Cleveland Clinic says. Eating large amounts of protein during this process prevents the body from using its own protein stores in muscles, tissues and cells for energy. The rapid breakdown of fat produces waste substances called ketones that are excreted through urine, a condition called ketosis. The protein-sparing diet thus is a ketogenic diet. Loss of appetite is common during ketosis, which adds to the weight loss.

Diet Features

The protein-sparing diet allows only lean meat, poultry, seafood and a small number of low-carbohydrate vegetables, according to the Cleveland Clinic. The diet does not allow additional types of fat or other carbohydrates. Any missing required nutrients are provided through supplements. You follow the diet until reaching your target weight and then gradually reintroduce carbohydrates and decrease protein in a post-diet process called a refeeding phase. This phase implements principles of a well-balanced diet to ensure future weight control.

What the Research Says

A study published in the October 1985 issue of the "American Journal of Public Health" evaluated the effects of the protein-sparing modified fast along with education, behavior modification and exercise on 668 obese participants. The average duration of the diet was 17 weeks, along with nine weeks in the refeeding phase. Average weight loss was 47 pounds, but this includes participants who stayed on the diet for only five weeks, and some people lost up to 76 pounds. There was an average regain of 6 pounds during the post-diet phase. Participants generally experienced a significant drop in blood pressure and triglyceride levels. The most successful participants were those who had been the heaviest and those who followed the diet and the post-diet phase for the longest time.

Things to Consider

When a person severely restricts carbohydrate intake and the body uses up its stored supply, the process eliminates a large amount of water. This can lead to dehydration and electrolyte imbalances, one reason medical supervision is important during the protein-sparing diet. Your doctor or dietitian will recommend how much fluid, sodium and potassium you should have each day. In addition, eating foods not allowed on the diet can disrupt the ketosis process and lead to dangerous imbalances in fluid and electrolytes, as well as interfere with weight loss, cautions the Cleveland Clinic.