Obesity in the elderly: Should we be using new diagnostic criteria?

Abstract

EDITORIALThe proportion of elderly people is growing in almost every country. This conveys a higher rate of diseases associated with age among which nutrition-related disorders are many. Proteinenergy malnutrition is highly prevalent (about 50%) in institutions and acute care units. Obesity is another issue that is raising increasing attention. The proportion of persons "diagnosed as obese" is higher in the elderly than in their young pairs. For example, in France, the latest survey conducted in 2006 (1) shows than the mean prevalence of obesity is 12.6, but more than 15% in those aged 65 years and above. Since obesity is associated with co-morbidities, it follows that at least one out of 5 of the patients in our wards are likely to be obese.Obesity is diagnosed as a BMI (Weight/Height²) higher than 30 kg/m² (2). This is the criterion that is used to estimate the prevalence irrespective of age. However, although it is true that weight tends to increase with age (3), the increase in BMI is also associated with a reduced height. It is estimated that height decreases by 8 cm in women and by 5 cm in men between 20 and 85 years of age (4-5). Therefore BMI naturally increases with age and mean values at 65 years are around 26 kg/m², higher than 25 and in the group of patients classified overweight. Each cm loss in height increases BMI between 0.2 and 0.3 units (for heights between 150 and 180 cms). Despite this mathematical artifact, the increased prevalence between 2003 and 2006, on the same French population (1) suggests that there is indeed an growing number of people with a high BMI as age increases.Body composition changes with age: fat mass increases especially in the central area of the body and is said to double between 20 and 85 years of age (6). Fat-free mass decreases by 15% over the same age range and more than 2/3 of the decline is made of muscle (6-7). Muscle tissue is infiltrated with triglycerides (8). This means that the BMI-%fat relationship varies with age. Figures 1 and 2 illustrate this concept, with a higher fatness for a given BMI as age increases. Furthermore, since there is a decrease in lean mass, a high BMI in a young adult (high lean mass, high fat mass, 9) corresponds to a different body composition in an older person (low lean mass, high fat mass). Further to this basic difference in body composition are the concepts of 1) sarcopenic obesity, with an increased fatness and a very low muscle mass, which carries specific consequences (10), and 2) an increased deposition of fat in the abdomen which drives metabolic consequences.The BMI cut-offs to define obesity have been chosen because of an increased all cause mortality as BMI increases above 25 kg/m² (2). In the elderly, this relationship is not the same. In a cohort of 13,000 subjects from California, aged 73 at study entry and followed up for 23 years, the adjusted relative risk of death is 1.35 before 70, 1.33 between 70 and 75, 1.12 above 75 and 1.22 above 80 years (11). Zamboni et al have reviewed (4) carefully this relationship. It l...

Age-related and disease-related muscle loss: the effect of diabetes, obesity, and other diseases

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Comparison of serum prohepcidin and iron metabolism parameters in obese and non-obese elderly individuals

“…In addition, BMI has been widely used and accepted as a simple method to classify medical risk by weight status. The results show that BMI provides a measure of the relation between height and weight and correlates with body fat percentage in young and middle-aged adults [26][27][28]. In elderly people, age-related changes in body composition (i.e.…”

“…In elderly people, age-related changes in body composition (i.e. decrease in lean body mass and increase in fat mass) and loss of height caused by compression of vertebral bodies and kyphosis [26,[28][29] alter the relation between BMI and percentage body fat. In addition, especially for those in late old age and / or very late or hospitalised patients, are observed disturbances in water and electrolyte balance.…”

Self-Reported Height, Calculated Height, and Derived Body Mass Index in Assessment of Older Adults

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