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1 From the Nutrition and Toxicology Research Institute Maastricht, Department of Human Biology, Maastricht University, Maastricht, Netherlands (MAvB), and the Institute for Health Sciences, Vrije Universiteit, Amsterdam, Netherlands (TLSV)
2 Address reprint requests to MA van Baak, Department of Human Biology, Maastricht University, PO Box 616, 6200 MD Maastricht, Netherlands. E-mail: m.vanbaak{at}hb.unimaas.nl.
See corresponding article on page 1317.
Villareal et al (1) address a major public health issue in their study in this issue of the Journal. As they describe, coronary heart disease is still a major cause of death. The prevalence and severity of cardiovascular disease risk factors increase with age, and these risk factors remain powerful predictors of cardiac events even in old age. Because obesity is associated with an unfavorable cardiovascular disease risk profile, an increased prevalence of obesity in old age endangers the healthy life expectancy that has increased over recent decades. Obesity is clearly associated with a decrease in life expectancy (2) and with an increase in unhealthy life-years (3). High fatness, rather than low fat-free mass, predicts disability in subjects aged 65–100 y (4). Villareal et al (1) report the effects of a lifestyle intervention consisting of an energy-restricted diet, supervised exercise training, and behavioral therapy on metabolic risk factors in frail, obese, elderly persons. In another article about the same study, the effects on body composition and performance variables were reported (5).
Although no controversy appears to exist concerning the benefits of an improvement in cardiovascular disease risk factors in the elderly, the benefits of weight loss are much debated, especially in frail elderly persons. Frailty is often regarded as a "wasting" disease, and weight loss, which leads to further wasting, may therefore be contraindicated. The authors mention 2 other reasons why weight loss may not be beneficial in the obese elderly population: the relative risk of mortality associated with obesity decreases with aging, and the body mass index (BMI) range associated with the lowest mortality risk increases with aging. An additional reason for skepticism regarding obesity management in the elderly is the notion that BMIs and obesity rates decrease after age 65 y.
Insights regarding these issues have changed dramatically. Although relative risk indeed decreases with aging, the absolute risk of mortality associated with obesity increases (6). Thus, the difference in absolute risk between an obese and a normal-weight person is high in the elderly. Even if the relative risk is low, the proportion of mortality attributable to obesity in the elderly is high because of the high proportion of obesity in this age category. The prevalence of obesity at age 60 y is more than 3-fold the prevalence in persons aged 20 y. In a comparison of different studies, each having a different baseline age, the optimal BMI associated with the lowest mortality risk seemed to increase when studied on a population level. However, it is important to note that individual increases in BMI are linked to increased mortality risk. Thus, weight-gain prevention is important for mortality risk reduction. The notion that obesity rates decline after age 65–70 y is based on cross-sectional studies. Cohort effects are likely to explain the differences between cohorts aged <65 y and those aged >65 y, which means that these cohorts differ not only in age but could differ also by historical background. An extreme example would be that being raised during a war has an effect on risk profiles throughout life. Longitudinal analyses from the Netherlands Research Programme Weight Gain prevention study showed that obesity rates still increase after age 60 y (7).
As shown in the study by Villareal et al (1), a diet and exercise program in older obese persons results in the expected improvement in cardiovascular disease risk factors, ie, those observed in younger age groups, without negative effects on frailty indexes (4). It is likely that exercise training plays an essential role in preventing the negative effects of weight loss on frailty variables by minimizing the loss of lean body mass that usually accompanies diet-induced weight loss. It may also help to prevent the reduction in bone mineral density that is associated with diet-induced weight loss in overweight elderly persons (8) and may increase the risk of fractures, although this remains to be shown in the context of the study by Villareal et al. Whether the macronutrient composition of an energy-restricted diet, especially the protein content, also plays a role requires further evaluation.
The findings of Villareal et al support a positive effect of a lifestyle change, with respect to diet and physical activity, on the cardiovascular disease risk profile of obese elderly persons. The study design, a randomized controlled trial, is deemed the gold standard for medical research. Some disadvantage of such studies are the small number of subjects, the potential selective participation of the subjects, and a clinical setting that is different from the real, obesogenic world in which unhealthy choices are more easily made. Valuable evidence for a role of lifestyle in metabolic risk factors in the elderly may come from large cohort studies of the relation between lifestyle, adiposity, cardiovascular disease risk factors, and a healthy life expectancy. A recently published study by Manini et al (9) on the relation between daily activity energy expenditure and mortality in >300 older adults provides additional insight into the important role that physical activity plays in the mortality of older people. Large intervention studies should focus on both environmental and implementation issues. From intervention studies in younger adults, it is known that most programs are effective for the duration of the intervention program and that the effects decrease thereafter.
Although frailty is an issue in the elderly, obesity and the metabolic syndrome constitute an increasing health threat in this age group. Whereas public health research during recent decades has introduced successful changes that have increased healthy life expectancy, the obesity epidemic will increase the number of unhealthy life-years at the end of life if no action is taken.
ACKNOWLEDGMENTS
Neither of the authors reported a conflict of interest.
REFERENCES
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