Does Short-Term Weight Loss Reduce Cardiovascular Risk?Monday, May 26, 2014
If you believe recent media headlines describing the findings of a paper published in The Lancet last week, you may be convinced that any weight loss – even if you don’t keep the weight off – reduces your risk for cardiovascular disease.
The study, reports on the relationship between lifelong patterns of BMI and cardiovascular risk a 60-64 year-old British birth cohort born in 1946.
Participants were classified as normal weight or overweight or obese based on heights and weights measured during childhood (at ages 2, 4, 6, 7, and 11 years) and adulthood (at ages 36, 43, 53 and 60–64 years).
As may be expected, various measures of cardiovascular and metabolic risk factors were positively related to extent and duration of adiposity.
There were, however, two findings that may seem rather unexpected:
Firstly, adiposity in childhood did not seem to matter as a predictor of CV risk in adulthood.
Secondly, it appeared that individuals who dropped at least one BMI category at any time during adulthood, irrespective of whether or not this weight loss was maintained, had lower cardiovascular (but not diabetes) risk than did those who never lost weight.
From these findings the authors conclude that,
“…cardiovascular benefit might arise from weight loss in adulthood, irrespective of when this weight loss is achieved, and support public health policies for lifestyle modifications for prevention and management of overweight and obese individuals at all ages.“
While it is easy to see why sustaining weight-loss as an adult (particularly if you have risk factors for cardiovascular disease) may well be beneficial, it is hard to imagine a plausible biological pathway that would link a “short-term” weight loss to long-term improvements in cardiovascular risk.
Indeed, the authors provide no explanation for their findings. They also provide no further information on the people who lost weight compared to the people who did not.
My first response would be to look for biological plausible confounders – were people who lost weight at anytime as adults perhaps more conscious or concerned about their health than those who did not? Or, were they more metabolically healthy to start with?
Let us also not forget that this was merely an observational study – association does not prove causality.
This is not to say that the findings are entirely implausible. There is some literature on the long-term “legacy effect” of lifestyle interventions on metabolic risk factors – but the biological basis for this is unknown and some colleagues doubt wether this effect really exists.
Given that weight regain is rather common after weight loss, it will be interesting to see if other studies can demonstrate lasting benefits of short-term weight loss.
At this time some scepticism may well be warranted.