Body Weight

Abstract

The foregoing chapters described energy balance as a function of: energy intake, macronutrient intake, substrate oxidation; and, energy expenditure as: basal metabolic rate, diet induced energy expenditure and activity induced energy expenditure. Direct effects on energy balance, and indirect effects on body weight and body composition were dealt with. The evidence presented originated primarily from fundamental research and has translational aspects for food production, like in poultry, or for physical activity, like in competitive sports. Specific clinical applications were shown in research on energy requirement in critically ill children and in patients with chronic obstructive pulmonary disease. Additionally, there is another obvious and relevant clinical application. The alarming increase of the incidence of overweight and obesity, with the increasing risk of developing diabetes, cardiovascular disease and cancer, requires science-based methods to decrease body weight and primarily body fat. Theoretically, energy balance is affected by behaviour like physical activity, energy intake and environmental changes affecting these two factors. The three aspects will be explained with specific studies where environmental changes are for instance actively moving to a new environment, going to high altitude, or seasonal changes in the same location. An increase in physical activity, by taking up exercise training, induces an increase in energy expenditure. However, energy balance is hardly affected as the training induced increase in energy expenditure is compensated for by a training induced increase in energy intake as well. An activity resulting in weight loss is high-altitude climbing. However, the high-altitude climbing induced weight loss is not primarily caused by increased energy expenditure. Exposure to high altitude reduces appetite and thus energy intake. The result is an energy deficit and weight loss. Staying in the same location with regard to altitude, body weight shows seasonal fluctuation. Weight goes down in spring to increase again in autumn. Seasonal weight fluctuations are rather the result of variation in energy intake than variation in physical activity. A potential modulator is ambient temperature. Intake goes down when temperature increases in spring and goes up again when it gets colder in autumn. Thus, the negative energy balance in this case is mainly because of a reduction of energy intake. Adopting an energy-restricted diet is an effective method to reduce weight. Theoretically, one could consume less of all three energy-providing macronutrients: less fat, less carbohydrate and less protein. In practice, maintaining or increasing protein intake while decreasing fat and carbohydrate intake, increases successful maintenance of a new, lower, body weight.KeywordsAmbient temperatureExercise trainingHigh altitudeHypoxiaMorbid obesityObesityPhysical activitySeason