The advice against low carbohydrate diets in this editorial is not justified by the article to which it refers. The two commentators misread the evidence and exaggerate its implications.

They contend that the “long term health effects” of such diets override the short-term weight losses that make them so popular. In support, they interpret the article by Lagiou et al as showing “adherence” to such diets over 15 years.

It does no such thing. Even the authors do not claim that. They imply that subjects maintained their low carbohydrate diets, but never say so explicity.

They could not demonstrate “adherence” for a simple reason. They only measured food intakes once, at the beginning of the study. Over the following decade and a half, they never even attempted to assess what subjects were eating.

This is an extreme example of a fundamental problem in most diet studies, the inadequate measurement of food intakes (1). The commentators disregard or fail to see the limitations of the study.

Their comments carry a sharp irony. They dispagage “lay people” who find low carbohydrate diets “appealing”, without having full information about them. They should apply the same standards to themselves.

The flaws in the primary data mean that the Lagiou article does not allow us to draw any conclusions about the long-term effects of low carbohydrate diets, for or against. Thus, the commentators’ conclusions are premature, excessive, perhaps even wrong.

(1) Winkler J, The fundamental flaw in obesity research, Obesity Reviews, (2005), 6, 199-202. jtw@blueyonder.co.uk

Competing interests: None declared