Albumin and labile-protein serum concentrations during very-low-calorie diets with different compositions
Article Abstract:
The visceral proteins are blood proteins that reflect the nutrition of an individual; in malnutrition they decrease, and when the diet improves they return to normal. Of the visceral proteins, albumin has the longest half-life and so is least sensitive to recent changes in nutrition. Albumin does reflect malnutrition that persists over time, once the time lag required for albumin to show signs of depletion has passed. Prealbumin and retinol-binding protein (RBP) have a shorter half-life and the blood levels of these two proteins drop quickly when nutrition is inadequate; they are more sensitive to dietary changes than albumin. A study was performed to compare five reducing diets in terms of their effects on the visceral proteins. Of the five diets, four were considered very-low-calorie diets (VLCD) because they provided no more than 500 calories per day (range: 180 to 500 calories.) Two of these four diets provided carbohydrate and protein, and the other two supplied all the calories from protein. The fifth diet was a less severe energy restriction, 1,200 calories per day, including protein, carbohydrate and fat. Thirty-four severely obese adult subjects were assigned to one of the diets for 20 days; the study was carried out while subjects stayed in a metabolic research unit. Measurements of the visceral proteins showed that, during the 20-day period, albumin remained unchanged with all of the diets. Prealbumin and RBP did not change on the 1,200 calorie diet, but decreased significantly on all four VLCDs. These results demonstrate that nutrition was adversely affected by the VLCDs, and that the provision of carbohydrate and protein versus only protein had no significant impact on reducing RBP and prealbumin. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Clinical Nutrition
Subject: Health
ISSN: 0002-9165
Year: 1990
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Increased muscle dynamic endurance associated with weight reduction on a very-low-calorie diet
Article Abstract:
Little is known about how dieting affects an obese person's muscle strength and endurance. Previous research has suggested that the composition of muscle fiber in obese individuals differs from that of normal-weight persons; obesity is associated with good muscle strength and poor muscle endurance. It is also known that during starvation, as occurs when a person fasts or follows a very-low-calorie diet, the body breaks down muscle tissue to obtain the protein it needs to survive. This process is referred to as skeletal muscle wasting. The degree of wasting can be used as an indicator of the person's nutritional state. For example, persons with anorexia nervosa, who deny themselves an adequate food intake, have little muscle power and fatigue quickly. A study of muscle function was performed with 32 obese women who followed a four-week very-low-calorie diet (544 calories/day) that was high in protein. The subjects lost weight, achieving a reduction in the ratio of waist circumference to hip circumference. The very-low-calorie diet led to a temporary reduction in muscle strength, which reflected the decrease in lean body mass. Muscle endurance improved; this was probably due to a partial shift in the energy source used by muscle tissue, from glucose to fatty acids. The changes in metabolic processes such as insulin sensitivity, glucose metabolism and glycogen utilization are also discussed in detail. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Clinical Nutrition
Subject: Health
ISSN: 0002-9165
Year: 1990
User Contributions:
Comment about this article or add new information about this topic:
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