Eddy Newton suggests in “State primaries must get moving to beat obesity” (20 September) that he sees sport as the universal cure-all. On the basis of a “straw poll” approach to data, the chair of the Independent Association of Prep Schools argues that children attending private schools are not as likely to be obese as those at state primaries. He then makes the enormous leap of assuming that it is the extra physical education and sporting opportunities offered by fee-paying schools that make the difference. Might there be other causal factors? I should think that spending on fruit and vegetables and education about healthy cooking and eating might differ somewhat between these two groups. I do not imagine many of the children attending private schools have the poor-quality, carbohydrate- and fat-heavy diet that many less well-off families live on. There are no kumquats, nor sushi, at food banks.

Kay Bowen, Southampton.