Exercise intensity does not affect the composition of diet- and exercise-induced body mass loss

Article Abstract:

Reduction of calories in the diet typically causes loss of both fat and fat-free tissue (such as muscle and body water). The effect of different diet and exercise combinations on the type of body weight lost is complicated and not always easy to predict. In one study, the weight lost by persons who dieted and exercised was 79 percent fat (and 21 percent fat-free tissue), while weight lost by those who only dieted was 68 percent fat. The proportion of body weight lost as fat can be increased if the dieter starts exercising and adjusts caloric intake upwards to support the exercise, but if exercise is added to a constant calorie restriction, the percentage of weight lost as fat may not increase. In this study, the effect of exercise intensity on the type of weight lost by dieters was measured. Twenty-seven obese women all followed a 1,200 calorie per day diet, while exercising three days a week for eight weeks. Using ergometers, thirteen women exercised intensively for 25 minutes per day and the other 14 women exercised at a slower pace for 50 minutes per day. The women who exercised for shorter sessions worked at a faster rate than those who had the longer sessions; the caloric expenditure was approximately the same for the two groups. The proportion of fat versus muscle mass lost over eight weeks was compared between the two groups; body composition was assessed by underwater weighing. The two groups did not differ on the composition of weight lost; for both the weight lost was approximately 80 percent fat. It was expected that the low-intensity regimen would cause a greater proportion of weight to be lost as fat. Perhaps this did not occur because both regimens did not involve exercise of great enough frequency or duration to show a difference between them. In conclusion, the choice between high- and low-intensity exercise as part of a weight-loss program should be left up to the individual and the physician. (Consumer Summary produced by Reliance Medical Information, Inc.)

Body weight, Reducing exercises

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Effects of cardiac stress during a very-low-calorie diet and exercise program in obese women

Article Abstract:

The safety of very-low-calorie diets (VLCDs) has been questioned; 60 deaths were associated with these diets in the 1970s. The diets typically contained collagen, a poor-quality protein, and inadequate amounts of vitamins and minerals; in some cases, there was no doctor supervision. Many of the people who died while following VLCDs had chronic diseases that may have contributed to their deaths. One report documents 17 persons who died while on VLCDs who had no known predisposing medical condition; electrocardiogram (ECG) results of some of these individuals indicated cardiac arrhythmias, or abnormalities in heart rhythm. A study was performed with 24 obese women who followed a VLCD (660 to 720 calories per day) for six weeks. The safety of this diet was evaluated by giving the subjects stress tests; these tests can induce cardiac arrythmia in patients who are susceptible. Cardiac tests were performed before, during, and after the six weeks of dieting; no abnormal changes in ECG readings were noted. These results support the assumption that VLCDs are safe for use by normal, healthy overweight women under the study conditions. The study diet supplied over 650 calories per day, included adequate amounts of vitamins, minerals, and high-quality protein, and subjects were monitored for six weeks. A VLCD supplying fewer calories or less nutritional quality may not be as safe. (Consumer Summary produced by Reliance Medical Information, Inc.)

Safety and security measures, Causes of, Arrhythmia, Low-calorie diet, Low calorie diet

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Weight loss in 108 obese women on a diet supplying 800 kcal/d for 21 d

Article Abstract:

In the first few days on a weight-loss diet, many people lose weight rapidly. Their rate of weight reduction often slows down considerably after this initial loss, even if caloric intake remains the same. This pattern causes many dieters to give up on the diet or become discouraged with their performance. The progress of 108 obese women on an 800 calorie per day regimen was followed. Several actually gained weight in the first few days; only after 13 days was every participant below her weight on admission to the program. Some women took up to two weeks to establish their individual rate of weight loss. The early large weight loss of some and the slight gain of others can be explained by shifts in the body's water content. Gains and losses of water do not reflect the loss of fat that dieters desire. A person who gains weight initially may be retaining water while actually losing fat. Weight changes during the first week on a new diet may not represent the long-term effect of the diet for the individual, and may instead deceive or confuse the dieter. In this study, intake was strictly set at 800 calories because the women were living in a metabolic ward, where food intake was controlled and measured. The average total weight loss in three weeks was 11 pounds.

Psychological aspects

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