The evaluation of weight in an older person is pathognomonic of the challenges of geriatric medicine, requiring integration of information on normative biologic change with age and past individual health behaviors to assess future risk. Although weight is one of the easiest clinical measures to obtain, the interpretation of weight in the geriatric patient and assessment of the need for intervention on weight is far more difficult. This chapter provides a rationale and recommendations for an approach to weight in older patients.
Body weight is an important contributor to health in old age. However, health practitioners are often skeptical about evaluating weight in older patients because it seems unlikely that this evaluation will change clinical treatment, except in the event of clear-cut weight loss. In practice, many of the health issues of old age are linked to weight. Clinically, weight stability is used as a sign of general health status. Weight is a contributor to the most problematic syndromes in geriatric medicine, particularly comorbidity contributing to hospitalization and physical and cognitive decline, and resulting health care costs. With the development of new drugs for symptomatic relief of weight-related conditions such as osteoarthritis and with extension to older persons of established preventive treatments for hypertension and hyperlipidemia, polypharmacy is increasingly a weight-related health issue as well. Caring for older patients involves dealing with weight-related issues on a daily basis, even if not explicitly recognized as such.
Apart from weight-related diseases, change in body composition with age, particularly the loss of muscle and bone and the increase in fat, may independently contribute to decline in functional status and loss of independence. Osteoporosis, a disease of loss of bone structure and quality, is an important risk factor for fracture. The loss of muscle with age, termed sarcopenia, is hypothesized to contribute to disability. The increase in fat mass with age may contribute as well. Adipose tissue is now known to produce multiple endocrine factors, including proinflammatory cytokines such as interleukin-6 (IL-6). IL-6 is associated with body fat, independent of weight-associated health conditions, and is also an independent risk factor for physical disability and death. Thus even accounting for body weight, change in body composition with age may independently contribute to risk.
Caloric restriction consistently promotes longevity in laboratory animals, even when restriction is instituted in adult life. Restricted animals are thinner and weigh less, reflecting their lower calorie intake, but lower weight alone does not completely explain the protection from disease and the survival advantage. Nonetheless, lower body weight appears to mediate fundamental physiological processes associated with health and longevity.
Prediction of body weight from metabolic measures is similar in older and younger persons. Total energy expended daily reflects resting metabolic rate, the energy used for digestion (thermic effect of food), and physical activity. Doubly labeled water studies for total energy expenditure (a gold standard technique that uses CO2 production to calculate activity over a specified period ...