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Fasting isn't an ideal way to diet

Question: What do you think of fasting one or maybe even two days a week to control weight? A friend of mine does this, and I am thinking of trying it.

Answer: Fasting for 24 hours may be an effective means of weight control, for some people. But doing this regularly isn't really a good idea. One main reason is you can lose muscle by starving yourself like this. In broad strokes, here's why.

Six hours or so after the last meal, your body will start to use stored carbohydrates (glycogen). Before the end of the fasting day, this source of energy will be exhausted. Your body will then turn to its other fuel stores _ fat and protein. Initially, protein (which comes from muscle) plays a prominent role. This is because it takes a few days on a starvation diet for your body gradually to adjust to obtaining most of its energy from stored fat.

The amount of protein lost in a single fasting day is small, roughly between 1 to 2 ounces a day. But the cumulative effect, over months or even years, could be substantial if the protein is not adequately replaced by eating properly and exercising on non-diet days. Exercise is very important, of course, since without it you can't build muscle mass, regardless of your diet.

The most reasonable way to lose weight is to eat consistently a balanced, low-calorie, low-fat, high-carbohydrate diet and to exercise. However, if you decide to fast, do so in moderation. On your fast days eat a minimum of 1,000 calories, including some protein (that's not much food), and drink plenty of water. And don't start restricting your diet like this for more than a day a week without consulting your doctor or a dietitian.

Mitral Valve Prolapse won't affect exercise

Question: I am a 66-year-old widow in good health, but I have a heart problem called Mitral Valve Prolapse (without regurgitation). Can you tell me about it? Does one's heart enlarge? Can I exercise, or will it increase the heart size?

Answer: The mitral valve controls the movement of blood between the left atrium (upper part of the heart) to the left ventricle (lower part). It consists of two leaf-like membranes that are reinforced by fibrous tissue and contain a few muscle fibers.

Mitral Valve Prolapse (MVP) is a slight deformity of this valve. That is, when the left ventricle contracts to propel oxygen-rich blood to the body tissues, the mitral valve balloons into the left atrium and decreases the valve's efficiency. In some cases, the valve may not close properly. Consequently, when the ventricle contracts, some blood can leak (regurgitate) into the atrium. The exact cause of MVP is unknown, although it may be of genetic origin, or occasionally it can result from rheumatic fever or heart disease.

The condition is usually harmless, and it is a fairly common one, affecting up to 5 percent of the population. According to Dr. Marian Limacher, a University of Florida cardiologist, unless the valve isn't closing as it should, and there is serious regurgitation, the MVP is seldom associated with an enlarged heart. As far as exercise is concerned, Dr. Limacher says that normally there are no restrictions. Of course, before you start an exercise program, you should talk all this over with your doctor.

Write with questions to Dr. Patrick J. Bird, Dean of the College of Health and Human Performance, University of Florida, Gainesville, Fla. 32611.