Protein-sparing modified fast

A protein-sparing modified fast (PSMF) is a very low calorie diet with some protein, fluids, and vitamin and mineral supplementation. The diet is to last about eight months. While people often lose weight they frequently regain it afterwards.

PSMFs were first designed in the 1970s. Health concerns include dehydration being a health concern, hence fluids, vitamin and mineral (potassium, magnesium, sodium, and calcium) supplementation is mandatory and doctor's supervision is recommended. PSMF diets consist of foods that are naturally rich in good-quality protein and particularly extremely low in fats (chicken breast, extra lean beef, tuna, egg white, ham, cottage cheese) Several programs derived from the original PSMF have been created such as the Dukan Diet, incorporates resistance training to minimize or prevent LBM breakdown, and minimal to no aerobic exercise (typically restricted to walking a few times a week).

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 PSMF 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. Typically, depending on activity level, .8-1.2 g per pound of lean body mass (not total body weight) is taken. Protein beyond this minimum amount is also eliminated, as the body would use it for energy. Further lean body mass (muscle, organs, etc.) are spared through resistance training and limiting aerobic activity.

For example, for a 225-pound male with 30% BF, and thus, 157.5 pounds of lean body mass and 67.5 pounds of fat, and weight trains three times a week, he would consume 1.0 g per lb of LBM * 157.5 lb of LBM = 157.5 g of protein which is 630 calories/day. With a fish oil supplemention (40 calories), and some minimal fat which is inherent in almost all foods, the total caloric intake could be around 800 calories/day. Protein powders are generally not recommended on this diet since whole foods lead to better satiety and this is an important factor on a very low calorie diet, though casein powder could be considered due to its ability to slow down digestion. Low calorie vegetables are required on the diet for the bulk, and fiber and carbohydrate-rich vegetables like corn, carrots, potatoes, etc. must be avoided on this diet. Any calorie-free fluids are permitted, including water, coffee, tea, and diet drinks.

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