Intended for healthcare professionals

Editor's Choice

Obesity and climate change

BMJ 2012; 345 doi: (Published 26 September 2012) Cite this as: BMJ 2012;345:e6516
  1. Fiona Godlee, editor, BMJ
  1. fgodlee{at}

“Childhood obesity, perhaps like climate change, is at times in danger of inciting an ennui borne out of a repetition of problems without answers, a long latency before problems become apparent, and a perception that solutions are out of reach.” So say Lee Hudson and Russell Viner in an editorial this week (doi:10.1136/bmj.e5457). They are commenting on a systematic review which concludes that the adverse effects of obesity on children’s health are greater than previously thought (doi:10.1136/bmj.e4759).

Based on data from nearly 50 000 children the review’s authors found that, compared with children of normal weight, those with a raised body mass index had significantly worse risk profiles for cardiovascular disease, including raised blood pressure, fasting insulin, and lipids. Overweight children were also more likely to have bigger left ventricles, suggesting that end organs are being affected.

As Hudson and Viner explain, these findings have worrying implications. We know from previous studies that childhood obesity increases the risk of cardiovascular disease in adulthood. But we don’t yet know whether this is because overweight children grow into overweight adults or because, as this study suggests, adverse physical changes are already taking place during childhood. Lots of methodological problems still stand in the way of unpicking this conundrum, and many questions remain. Is the link between overweight and cardiovascular risk linear or is there a threshold? How much weight do these children need to lose to improve their cardiovascular risk? And what role does puberty play?

Given the enormity of the problem globally, we can’t wait for answers to these and other important questions before taking action. But what to do? Better diets and more physical activity, of course. But how do we achieve these things at the individual and population level? Two randomised trials in the New England Journal of Medicine last week, summarised in Research News (doi:10.1136/bmj.e6442), provide strong evidence that sugary drinks really do cause obesity. So policy makers should take note.

As for exercise, I was surprised to read in Mark Hamer and Abigail Fisher’s editorial that the evidence linking physical activity with obesity is weak (doi:10.1136/bmj.e6320). Interventions that aim to increase physical activity have been found to have little effect on obesity. But as Brad Metcalf and colleagues conclude from their systematic review (doi:10.1136/bmj.e5888), this is probably because the interventions don’t actually increase activity very much. Importantly, the authors looked only at studies that included an objective measure of physical activity rather than relying on self reports.

Obesity and climate change are linked in more ways than just the immensity and apparent insolubility of the challenge. High carbon lifestyles damage our bodies and the planet. Tackling both obesity and climate change requires radical but synergistic changes to the way we live. Medicine may seem only a small part of the picture in each case. But in both of them, through contact with individual patients and influence at all levels of policy making, doctors have a crucial part to play.


Cite this as: BMJ 2012;345:e6516


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