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The impact of obesity on the elderly

We know that obesity in adults is linked to serious conditions such as heart disease and diabetes, and last week I reported on a study that links obesity to disability and its impact on the cost of health care (The long term consequences of obesity, 4/25/07). In fact, for those under 55, studies show that a lower Body Mass Index is directly related to the lowest mortality rates from all causes. But the inverse appears to be true for the elderly: some studies seem to link a BMI of 27 to 29 (near-obese) to a reduced risk of mortality. This is by no means certain, however, as studies can be flawed and we also know that Body Mass Index is not as accurate a measure of body fat in the elderly as it is in the adult population.

A recent study in the Archives of Internal Medicine (2007;167(8):774-780) looks at more than just mortality in the elderly but also looks at one indication of quality of life: disability.

For the purposes of the study, the researchers assessed a participant's level of disability by asking if they were able to perform certain activities of daily living without assistance. Those activities are: bathing, grooming, dressing, eating, using the toilet, walking across a small room, and transferring from a bed to a chair.

The study was based on a survey of 12,725 persons 65 or over living in five general areas across the United States. At the beginning of the study, none of the participants were disabled as defined in the study. Their Body Mass Index, as well as information on various health conditions, blood pressure, and upper and lower body physical functions were measured and recorded. For seven years the participants were recontacted yearly to reassess their disability status as well as their Body Mass Index and other measures.

After controlling for age, sex, marital status, whether the subject smoked or not and various medical conditions, the researchers found that although those who had a Body Mass Index between 35 and 40 (very obese) had no greater risk of death from all causes than those whose BMI was in the normal range, they were twice as likely to be disabled and unable to care for themselves without assistance. Those with a Body Mass Index of 25 to 30 (overweight), on the other hand, had the lowest risk of overall mortality and only a slight increase in their risk of disability.

What this means for you

These results should not be taken as a license to be overweight if you're over 65. My patients tell me all the time that their biggest fear for their older years is being unable to care for themselves. The take-home message here is that maintaining a normal weight throughout your life is still your best bet for a long, healthy, and independent life.

First posted: May 1, 2007