Objective: To understand the impact of the phenylethanolamine N-methyltransferase (PNMT) G-148A gene and nutritional variables on weight loss in obese women.
Research methods and procedures: One hundred forty-nine women, ages 45 to 65 with a body mass index of >30 kg/m(2), participated in a 6-month, open-label intervention that included sibutramine (15 mg/d) and a monthly health-education class. Anthropometric measurements, vital signs, food frequency, exercise log, medication compliance, and psychological and sociological questionnaires were completed each month. Genetic polymorphisms of PNMT were determined.
Results: Univariate analysis of G/G, G/A, and A/A genotypes against tertiles of percentage of weight loss were significant at 3 but not at 6 months (Pearson chi(2): p < 0.006; homozygous/heterozygosity: p < 0.002, p < 0.253, and p < 0.122, respectively). A regression model that included the PNMT genetic variation and certain nutrition and exercise variables demonstrated that only the PNMT gene (beta = 0.360, SE 0.585, and p = 0.003) was statistically significant at 6 months, and the total calories (beta = -0.925, SE = 0.004, and p = 0.009), fiber intake (beta = 0.621, SE = 0.124, and p = 0.000), and PNMT (beta = 0.262, SE = 1.415, and p = 0.024) were significant.
Discussion: The homozygosity/heterozygosity of the PNMT gene was highly predictive of significant weight loss with sibutramine during the first 3 months, which highlights the need for specific pharmacotherapy. The early weight-loss success of those subjects who were homozygous for PNMT may have motivated and selected those that would make further dietary changes, which then augmented their final weight loss.