Research shows that weight loss in the elderly increases all cause mortality, particularly when weight is lost from skeletal muscle. However, it is often difficult to differentiate between intentional weight loss and weight loss caused by illness, which confounds the results from research. Underlying illness may be a direct cause of rapid weight loss and lead to an increase in mortality risk. Although some studies have found improvements in quality of life and mobility in elderly subjects who lost weight, questions still surround the benefits of weight loss on mortality. The use of a properly controlled randomised trial to assess the effects of intentional weight loss on mortality has recently shown no benefit to weight loss in elderly subjects1. The study used data from the TONE study2 that was investigating the effects of sodium restriction and weight loss on blood pressure following the withdrawal of anti-hypertensive medication.
The 585 Overweight and obese men and women were randomly assigned to a weight loss intervention and a non-weight loss intervention, with and without sodium restriction, over 12 years of follow-up. At enrolment the subjects had systolic and diastolic blood pressure of <145 and <85 mmHg, respectively, and were taking an antihypertensive medication. The weight loss intervention was designed to cause and maintain a 4.5kg weight loss mainly by walking and the sodium restriction intervention limited sodium intake to ≤1800mg/d. The control group received no study-related counselling in either weight loss or sodium restriction. The results showed that the weight loss intervention subjects lost 3.9kg over 12 months, whereas the non-weight loss intervention lost just 0.9kg. Over the 12 year follow-up, 101 subjects died, but there was no significant difference in mortality between the weight loss, non-weight loss or low sodium groups.
Men assigned to the weight loss intervention did have lower mortality that those in the non-weight loss intervention, although the reduction was only from 2 deaths per 100 person years to 1.2 deaths per 100 person years. Addition of the TONE study data to data from the ADAPT study, gave the authors >900 subjects with which to assess the effects of weight loss and mortality. However, even with a larger subject number, there was still no significant effect of weight loss on all cause mortality. In addition, no significant effect on mortality was seen between the sodium restricted subjects and the non-sodium restricted subjects, which adds further evidence to the accumulating literature that shows that sodium restriction is not an effective treatment for blood pressure and does not affect mortality. Importantly, the study data did not differentiate body fat loss from muscle loss.
Subjects who lost more than the median body weight amount in the weight loss group had no significant difference in mortality to those who lost less than the median body weight. However, in the non-weight loss intervention, those subjects who lost more than the median body weight had a significantly (2.5-fold) increase in all cause mortality than those who lost less than the median body weight. This suggests that unintentional weight loss causes an increase in mortality, as has been suggested in other studies. There appears therefore, not to be a large benefit to intentional weight loss in older individuals in terms of all cause mortality. However, care should be taken to differentiate between intentional weight loss (that does not cause a significant increase in mortality) and unintentional weight loss, (that does lead to an increase in all cause mortality).
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