Blood samples and self-reported heights and weights have been collected from 114 vegans, 1550 vegetarians, 415 fish eaters who did not eat meat, and 1198 meat eaters. We have previously reported that mean total and LDL cholesterol were lower in the vegetarians and fish eaters than in the meat eaters, while the mean levels in vegans were lower still. We have examined the possibility that this relationship could be explained by differences in the mean body mass index of the four groups. While there was a small positive relationship between body mass index and plasma lipid levels this did not explain the previously reported difference between diet groups. After adjusting for the effect of body mass index there remained a small negative association between height and plasma lipid levels, which has not previously been reported. Height is known to be influenced by childhood ill health and has also been shown to be related to social class, and it may be that the relationship between plasma lipid levels and height can be explained by these factors.