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Rapid response to:

Research

Physical activity to prevent obesity in young children: cluster randomised controlled trial

BMJ 2006; 333 doi: https://doi.org/10.1136/bmj.38979.623773.55 (Published 16 November 2006) Cite this as: BMJ 2006;333:1041

Rapid Response:

Childhood obesity and gym membership

Sir

I commend the authors of this paper on their strategy – namely to try and look at an individual piece of the jigsaw that is obesity in a well constructed and conducted trial. Sadly, as everyone who has bought gym membership as a single intervention to lose weight would have told them, they were always on a losing wicket.

If we assume that a pound of fat requires roughly 3 500 kCals to be burnt off unreplaced, and that the most that many adults can burn off is no more than 10 kCals/min during cardiovascular exercise, one pound of fat’s worth of energy takes at least 6 hours of decent intensity cardiovascular exercise to lose if that is all you do different. I know there are a host of assumptions and fudge factors here, but the principle works.

I have no idea what the equivalent total would be for a group of overweight 4 year olds in a group at nursery, but I struggle to believe that we would expect 36 hours of this (assuming they attended and co- operated with every session and didn’t up their food intake afterwards) would be even close to enough to see a significant difference. Consequently, I don’t think this tells us anything we didn’t already know ie there are no quick fixes, exercise over a period of a lifetime is a good thing, and obesity is a lifestyle issue, encompassing diet, exercise, and a whole family approach to healthier living. Tough but true

Competing interests: None declared

Competing interests: No competing interests

22 November 2006
Ian P Rodd
Consultant Paediatrician
Royal Hampshire County Hospital, Winchester SO21 5DG