Factors affecting energy and macronutrient requirements in elderly people.

OBJECTIVES: (i) to describe energy and macronutrient requirements in healthy and diseased elderly patients from knowledge acquired about the age-related changes in energy balance (ii) to describe changes in body composition and the consequences of physical activity and exercise programs.
RESULTS: Aging in individuals considered healthy is associated with a reduction in muscle mass and strength (with consequences on autonomy), and an increase in fat mass mainly in the central area, the latter might increase the risk of cardiovascular disease. Body composition changes can be seen as a positive energy (fat) balance. The reduced fat-free mass is responsible for a low resting metabolic rate. Therefore, energy requirements are reduced all the more since physical activity is decreased. A simple means for calculating individuals' energy requirements from estimated resting metabolic rate and physical activity is not yet available in a validated form and is much required. Protein requirements are still debated. Exercise programs can be implemented for increasing muscle mass and strength (resistance training) or for improving aerobic fitness and reducing fat mass (endurance exercise). It is not yet clear whether structured exercise programs or spontaneous physical activity have similar advantages. It is not known in which cases resistance, endurance, or a combination of both exercises should be recommended. The consequences of physical activity and exercise programs on energy and macronutrient requirements is not clear. Diseased elderly persons are prone to malnutrition which impairs clinical and functional outcome. Malnutrition is the result of an energy intake inadequate to match energy requirements. Literature is very short of data on energy requirements in diseased elderly persons, who are under the complex influences of stress (increasing resting energy requirements), reduced body mass and physical activity (reducing energy requirements), plus potential effects of drugs. Almost nothing is known about macronutrient requirements.
CONCLUSIONS: Further studies are required to enable calculations of energy and macronutrient requirements of individuals, especially diseased. More work has to be done to understand the energy imbalance in the elderly (healthy and diseased). Careful evaluations of physical activity and exercise programs are necessary.