Protein Sparing Modified Fast

The Protein-Sparing Modified Fast, or PSMF, is a total fast modified by the intake of a bare minimum of protein, fluids, vitamins, and mineral supplementation.

PSMF was designed in the late 1970s as a diet for a rapid weight loss for the morbidly obese. PSMF is a type of very low calorie diet with dehydration being a health concern, hence fluids, vitamin and mineral (potassium and sodium) supplementation is necessary and doctor's supervision is recommended. PSMF diets consist in foods that are naturally rich in good-quality protein and particularly low in fats (chicken breast, egg white, ham, cottage cheese).

PSMF as a diet recently became popular due to the French Dukan diet. It is also used by professional bodybuilders.

Methodology
Complete fasting produces the largest possible calorie deficit of any diet. Long-term fasting, however, introduces multiple health risks which can lead to death. Even if major health problems are avoided, a complete fast results in the loss of muscle, organs, and other lean body tissue, while most dieters are only attempting to lose excess fat. This muscle-wasting effect is a natural consequence of a diet deficient in both calories and in protein.

A Protein-Sparing Modified Fast attempts to spare the dieter the health risks of a complete fast by introducing the minimum amount of protein necessary to prevent muscle-wasting effects, while still eliminating fats and carbohydrates. Protein beyond this minimum amount is also eliminated, as the body would use it for energy.

Any calorie-free fluids are permitted, including water, coffee, tea, and diet drinks.

The amount of protein consumed varies by individual. It is generally calculated based on lean body weight and adjusted based on activity level, but generally results in a net daily intake of well under 1000 calories.

In addition to lean protein, people on a PSMF consume supplements to avoid the nutritional deficiencies inherent in such an extreme and low-calorie diet. These include essential fatty acid supplements, vitamins, and minerals. A general multivitamin supplement, designed to augment a healthy diet, is inadequate - for example, someone on a PSMF needs significant amounts of minerals such as sodium and potassium, which would otherwise be supplied in the diet.

A long-term PSMF diet undertaken carelessly and without the care of a physician may lead to serious health risks.

Results
PSMF is a rapid fat loss protocol. In one study given over a six-week period, 15 obese patients were found to have lost 31.8 lb (14.4 kg) of body fat on average, while maintaining lean body mass.