Does Intentional Weight Loss Reduce Mortality?Wednesday, April 1, 2015
Given that virtually every risk-factor guideline (from hypertension to diabetes) recommends “weight-loss” as “first-line” treatment, to many this may seem a rather stupid question, but in reality, there is in fact almost no high-qulaity evidence to show that intentional (non-surgical) weight loss actually reduces mortality.
This may well be simply because randomised controlled studies on intentional weight loss have either never been long enough, big enough, or able to sustain large enough differences in body weight between the interventions arms.
Nevertheless, now a meta-analysis by Stephen Kritchevsky and colleagues from the Wake Forest School of Medicine, published in PLOS one, suggests that being randomised to the intervention arm in a weight-loss study may reduce mortality by 15%.
The researchers identified 15 randomised controlled trials of behavioural interventions for weight loss of at least 18 months duration, of which 12 reported at least one death in either of the intervention arms.
These studies included 17,186 participants (53% female, mean age 52 years, mean BMI range 30–46 kg/m2 ) with follow-up times ranging from 18 months to 12.6 years (mean: 27 months), and an average weight loss of 5.5±4.0 kg.
Based on a total of 264 deaths in weight loss groups compared to 310 in non-weight loss groups, the authors calculated a 15% lower all-cause mortality risk (RR = 0.85; 95% CI: 0.73–1.00) in the weight-loss group.
Thus, the authors conclude that being randomized to the weight-loss arm in a behavioural weight-loss study may indeed reduce mortality risk.
However, as readers may realise, this study certainly does not “prove” that it is the actual weight loss that mediates these effects. After all, to achieve and sustain weight-loss through behavioural interventions, participants would have had to change their diet and activity levels to a greater extent that those in the control group. Thus it is very possible that the difference in mortality between the groups could well have been due to changes in health behaviours rather than due to the actual weight loss.
Nevertheless, the findings are reassuring in that they at least do not show an increase in mortality, something that people have feared may happen with intentional weight loss, especially in older individuals.
I guess the most we can conclude from this study is that being lucky enough to be randomised into the “weight-loss arm” of a behavioural weight-loss RCT may just help reduce your mortality risk.