Table 2. BMI comparison by genotype and study group.

	VM/VV	MM	Mean difference in BMI MM vs VM/MM (95%CI)	P-value	Adjusted P
BWHHS	3468	163
BMI (mean±s.d.)	27.63±5.02	26.72±4.78	−0.911 (−1.70, −0.12)	0.023	0.030
ALSPAC	6253	225
BMI (mean±s.d.)	23.04±3.87	22.47±3.65	−0.57 (−1.08, −0.054)	0.030	0.021

Abbreviations: ALSPAC, avon longitudinal study of parents and children; BMI, body mass index; BWHHS, British women's heart and health study. The Va166Met genotypes has been labelled as MM: Met-Met; VM: Val-Met; VV: Val-Val.

Mean difference in BMI is the difference between two normalized means of two comparison groups (carriers of MM vs carriers of MM and MV) and are given in Kg/m². The mean values divided by an estimate of the within-group standard deviation have shown. Ages of participants were used as covariates in the association model in both studies, while alcohol consumption in ALSPAC and social class in BWHHS, both of which had shown weak associations with genotype (see Table 1), were also included as covariates in the adjusted P-values.