After 1 year , the decrease in glycosylated hemoglobin ( HbA1c ) levels in subjects with the heterozygous variant genotype ( GT ) was significantly greater than in those with the wild-type homozygote ( -2.2 % in GT vs. -1.1 % in GG , P < 0.05 ) after adjustment for baseline HbA1c levels , exercise and diet in each group .