Fit, fat and fat free: the metabolic aspects of weight control.

Nutrition and Toxicology Research Centre, University of Maastricht, The Netherlands. [email protected] This paper examines the role of energy expenditure, especially physical activity related energy expenditure, in the metabolic aspects of body weight regulation. New data have emerged from studies conducted over the last decade, demonstrating that physical activity is a critical factor contributing to successful body weight regulation in lean and obese individuals. A growing number of prospective studies show the protective role of increased physical activity against weight gain over time. Also, individuals who are successful in long-term maintenance of a weight reduction are highly likely to also be physically active. Participation in physical activity is among the best predictors of success in weight maintenance. Physical activity facilitates weight maintenance through direct energy expenditure and improved physical fitness. The latter facilitates the amount and intensity of daily activities. Both components are of importance in relation to energy and substrate balance. Exercise may act as a substitute for an enlarged fat mass, in bringing about rates of fat oxidation commensurate with fat intake. Metabolic effects on lipid mobilization and oxidation and morphological/biochemical changes in the muscle fiber, contribute to this successful regulation of body weight. A limited number of studies indicate that, the minimal level of additional energy expenditure by physical exercise required for protection against gain in excessive body fatness, is around 12 kcal/kg body weight/d. In conclusion, the amount of energy expended in physical activity, mediated by several metabolic factors, may play an important role in body weight regulation. Publication Types: Review Review, Tutoria

Physical inactivity and metabolic factors as predictors of weight gain.

Physical inactivity and metabolic factors as predictors of weight gain

Glycemic carbohydrate and body weight regulation

Glycemic carbohydrate and body weight regulation. Saris WH. Nutrition and Toxicology Research Institute, NUTRIM, University of Maastricht, PO Box 616, 6200 MD Maastricht, The Netherlands. The purpose of this review is to examine the relationship between glycemic carbohydrate and its effect on body weight regulation. By contrast to fat, carbohydrate has a positive impact on energy intake, energy expenditure, and body weight control. Despite some debate about the role of the carbohydrate-to-fat ratio in the diet and the prevalence of obesity, metabolic studies show that diets high in fat are more likely to result in body weight gain than diets high in carbohydrate. So far there are no indications that carbohydrate classes differ greatly with respect to energy expenditure and energy balance. However, the impact of carbohydrate source and class, as well as the form in which carbohydrate is consumed (i.e., solid or liquid) on body weight control requires further consideratio

Fat metabolism during exercise: a review--part III: effects of nutritional interventions.

Nutrition Research Center, Department of Human Biology, University Maastricht, The Netherlands. By changes in nutrition it is possible to manipulate fat oxidation. It is often theorized that increasing fat oxidation may reduce glycogen breakdown and thus enhance performance. Therefore, the effects of acute, short-term and long-term fat feeding have been subjects of investigation for many years. Ingestion of long-chain triacylglycerols (LCT) during exercise may reduce the gastric emptying rate and LCT will appear in the plasma only slowly. Medium-chain triacylglycerols (MCT) do not have these disadvantages and they are rapidly oxidized. However, the contribution of MCT to energy expenditure is only small because they can only be ingested in small amounts without causing gastrointestinal distress. So at present, fat supplementation in the hours preceding to or during exercise (either long chain or medium chain triacylglycerols) cannot be recommended. High-fat diets and fasting have been suggested to increase fatty acid availability and spare muscle glycogen resulting in improved performance. Both fasting and short term high-fat diets will decrease muscle glycogen content and reduce fatigue resistance. Chronic high-fat diets may provoke adaptive responses preventing the decremental effects on exercise performance. However, at present, there is little evidence to support this hypothesis. Also from a health perspective, caution should be exercised when recommending high-fat diets to athletes. Publication Types: Review Review, Tutoria