Body composition (adiposity) is generally understood to be the amount of lean body mass relative to fat mass. The National Institutes of Health (NIH) advocates use of body mass index (BMI=[weight (kg)/height(m²)] to characterize body composition) (NIH, 1998). Although underweight (BMI<18.5 kg/m²) is a problem for some older adults, overweight and obesity, which the NIH defines as a BMI of 25.0–29.9 kg/m² and≥30.0 kg/m² respectively (see Table 64.1), are far more prevalent. In the United States of America, between 1999 and 2002, the prevalence of overweight and obesity combined was 39.4% for 60- to 69-year-olds and 25.3% for individuals at least 70 years. Both mean BMI and the prevalence of overweight and obesity are increasing in all Western European countries, Australia, the US and China (Silventoinen et al., 2004).

Numerous untoward consequences are associated with increased body weight. Although overweight may have some survival benefit for adults 70 years or older (Flicker et al., 2010), obesity is associated with an estimated 111 909 excess deaths among older adults in the US (Flegal et al., 2005). Overweight and obesity are also accompanied by numerous comorbidities. The relationship between weight and type 2 diabetes is particularly strong, with Colditz et al. (1995) showing that women experience a 25% increase in the relative risk of diabetes for each added unit of BMI over 22.0 kg/m². Other comorbidities accompanying increased body weight in older adults are hypertension, coronary artery disease, stroke, respiratory problems (including sleep apnea), osteoarthritis and some forms of cancer (NIH, 1998).

Although mortality and comorbidities warrant attention, functional limitations accompanying increased body weight are particularly relevant to geriatric rehabilitation. The combination of decreased strength and increased body fat (which typically occur with aging) can render demanding activities, such as standing from a chair or climbing stairs, painful, difficult or impossible (Sarkisian et al., 2000; Larrieu et al., 2004; Bohannon et al., 2005; Bohannon, 2007). Consequently, it is essential that rehabilitation professionals address the body composition of their patients. Hereafter, some fundamentals of the examination of and interventions for overweight and obesity are covered.

Based on its practicality, BMI is recommended by the US Preventative Services Task Force for screening adults for obesity (McTigue et al., 2003). Indeed, the measurement of weight and height, on which BMI is based, is possible for most adults. When height and weight cannot be measured, they can be obtained by self-report. However, the accuracy of BMI may be compromised by the tendency of individuals to underreport weight and overstate height (Niederhammer et al., 2000). Regardless of the source of height and weight information, BMI has limitations. These include the propensity of older adults (particularly women with osteoporosis) to lose stature with age (Sorkin et al., 1999) and the failure of BMI to differentiate between lean body mass and fat mass.

Alternatives to BMI are available. Air displacement plethysmography (Fields & Hunter, 2004) and dual energy X-ray absorptiometry provide more specific information about body composition than BMI, but neither is widely available nor portable. Bioelectrical impedance is also more informative regarding body composition (Vilaca et al., 2011), and it is portable. However, it is influenced by hydration and other variables used in its predictive algorithms. Skinfold measurements are relatively easy to obtain, and measurements from a single site (e.g. subscapular) may be sufficient (Garn et al., 1971). The relationship between central adiposity and cardiovascular disease makes waist circumference a useful supplement to BMI (NIH, 1998). Waist circumference should be measured just above the pelvic crest, parallel to the floor, while the tested individual stands. A man is considered to be at high risk of weight-related comorbidities if his waist circumference exceeds 102 cm (40 in); for women the criterion is 88 cm (35 in).

For older adults who are overweight or obese, even small losses of weight have been shown to be highly advantageous. Larsson and Mattsson (2003), for example, found that obese women who achieved a 10% weight loss realized significant improvements in walking speed, oxygen consumption, pain and perceived exertion. Felson et al. (1992) reported that individuals who achieved a weight loss of 2 or more BMI units (about 5.1 kg) over a 10-year period reduced their likelihood of developing knee osteoarthritis by more than 50%. Given such findings, health professionals should not be shy about engaging older adults about their weight. Patients are generally desirous of advice about diet, assistance with setting weight goals, and recommendations regarding exercise (Potter et al., 2001). Adults with arthritis who receive advice from a health professional to lose weight are more likely than those not receiving such advice to make an effort to lose weight (Mehrotra et al., 2004).

There are five basic strategies that can be used alone or in combination to lose weight. They include: diet, physical activity, behavior therapy, pharmacotherapy and bariatric surgery.

Dietary therapy focuses on reduced daily caloric intake. Low calorie diets (800–1500 kcal/day) can reduce total weight by a mean 8% over a period of 6 months. Unfortunately weight loss thus achieved is usually not sustained (NIH, 1998).

Physical activity is often reduced in overweight and obese older adults. Those who walk less (Tryon et al., 1992) and sit more (Brown et al., 2003) are more likely to be overweight or obese. Aerobic exercise regimens, which serve to increase activity over baseline, are able to produce modest weight losses (3.0 kg for men and 1.4 kg for women) (Garrow & Summerbell, 1995). Such exercise can take many forms, but research indicates that older adults prefer walking as a mode of exercise (McPhillips et al., 1989). Employing a pedometer and having an exercise ‘buddy’ can be motivational for increasing walking activity (Thomas et al., 2012). For individuals unable to tolerate sufficient walking to achieve a therapeutic beneficial effect, alternatives not entailing full weight-bearing may be indicated. These include recumbent cycling or aquatic activities. Resistance exercise should also be considered as it can enable older adults to better handle their body weight and to increase their muscle mass and energy expenditure. In lieu of, or in addition to, formal exercise interventions, older adults can expend additional energy by walking rather than driving short distances, taking the stairs instead of the elevator or escalator, and forgoing use of ‘labor-saving devices’ (Lanningham-Foster et al., 2003).

Behavior therapy is multifaceted, but much of it is directed at altering dietary and exercise habits. Key components include, but are not limited to: training in self-monitoring, self-control, exercise and diet information, stimulus control strategies, reinforcement, problem-solving and goal-setting, behavior modification, family support, stages of change, cognitive restructuring, peer relations and maintenance strategies. Behavior therapy has been described as offering benefits that are supplemental to those provided by other approaches (NIH, 1998).

When more conservative approaches prove insufficient, drugs or surgery may be appropriate. Several drugs, including orlistat and sibutramine, can be prescribed. As part of a comprehensive program they can contribute to weight loss when used for 6 months to a year (NIH, 1998). For patients with severe obesity, bariatric surgery (either open or laparoscopic) is immensely successful in causing weight loss. Weight loss is greatest in the first year or two after surgery and ranges from 20% to 40%. In the Swedish Obese Subjects Study, patients’ weight losses were 16.3% after 8 years and 16.1% after 10 years (Sjöström et al., 2004). Bariatric surgery has a powerful effect on some of the comorbidities that tend to accompany obesity. Specifically, diabetes, hypertension and sleep apnea are resolved or improved in the vast majority of cases.