Metabolism and nutritional adaptation to altered intakes of energy substrates

Article Abstract:

Nutrition surveys have suggested that there is great variation in the amount of food energy consumed by individuals of the same age, size and sex. One study reported that for a pair of similar individuals, one person might eat twice as much as the other. Research projects in which people were overfed for a prolonged period showed that they did not necessarily gain the expected amount of weight, but instead increased their metabolic rate (energy expenditure) without increasing exercise. This is considered a form of biological adaptation, and the reverse process is thought to occur when people are underfed. In starvation, the rate at which energy is burned for basic body functions drops in order to protect the individual. However, a review of the literature suggests that the degree of adaptation is not as dramatic as previously thought. After correcting for changes in body weight and activity, no more than a ten percent adaptation in metabolic rate can be expected following a change in energy intake. During long-term overfeeding or underfeeding, metabolic efficiency will not make more than a ten percent compensatory adjustment. Results indicating that one of two comparable individuals ate twice as much as the other are most likely inaccurate. The composition of the diet, in terms of the percent of calories from fat, protein, and carbohydrate, does influence energy efficiency. Each of these substrates is metabolized by a different biochemical process, some of which use up more energy than others. Thus the body may utilize one calorie of fat more efficiently than one calorie of carbohydrate. When storing energy as body fat, it is easier for the body to deposit fat from food than to convert carbohydrate from food into fat. Populations that consume a high-fat diet may be more prone to obesity than societies that eat mostly grains, even when caloric intakes are equal. (Consumer Summary produced by Reliance Medical Information, Inc.)

Research, Evaluation, Laws, regulations and rules, Energy metabolism, Physiological regulation, Adaptation (Biology), Evolutionary adaptation, Metabolic regulation, Biological control systems

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Mother-daughter pairs: spinal and femoral bone densities and dietary intakes

Article Abstract:

Osteoporosis is a decrease in bone density, which can lead to fractures and is a serious health problem, particularly among postmenopausal white women. Many factors are thought to predict the development of osteoporosis, including extent of skeletal mass acquisition during adolescence and a family history of the disease. The characteristics of familial contributions to osteoporosis are unclear, however. Thirty-seven healthy mother-daughter pairs were evaluated for bone mineral density (BMD) and dietary intake to better characterize tendencies to osteoporosis in families. The BMD of all but one lumbar (low back) vertebrae and areas of the femur (thigh bone) of mothers and daughters correlated significantly, and values in mothers were all significantly lower than daughters. The BMD values of the mothers ranged from 78 to 98 percent of those of young healthy subjects, while BMD values of daughters averaged 102 percent of young healthy (control) subjects. Correlation of mothers and daughters tended to be better for mothers who were premenopausal. Dietary intake of mothers and daughters did not correlate well. Dietary intake of calcium correlated in daughters to BMD of three bone sites, but other dietary intake in daughters or mothers was not associated with BMD. The study suggests that at least two familial components affecting bone mass density may exist. One may influence initial attainment of bone mass, while the second may influence postmenopausal hormonal changes which affect bone mass. The study indicates that BMD similarities exist between mothers and daughters and suggest that identification of young women at risk for OP is possible with identification of older women with OP. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Genetic aspects, Osteoporosis, Bone densitometry

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