Impact of a FTO gene risk variant on variables of energy metabolism in adults with obesity class 2 and 3

PURPOSE: The metabolic consequences of carrying a FTO obesity-promoting risk allele have not been fully elucidated and may be confounded by obesity per se. Against this background, we investigated the impact of FTO allele (SNP rs9939609) on fasting and postprandial energy expenditure and fasting substrate expenditure in a study population of uniformly and similarly obese individuals. PROCEDURES: We studied a similar number of participants with BMI classes 2–3 (median BMI 42.8 kg/m(2)) who were either homozygote for the non-risk allele TT (n = 33, numbers increased by enrichment), heterozygote (AT) (n = 32), or homozygote for the risk allele AA (n = 35). MAJOR FINDINGS: Basal metabolic rate and postprandial energy expenditure did not differ between FTO-groups. However, fasting respiratory quotient (RQ) was increased in those carrying ≥1 risk allele (p = 0.008), whereas postprandial RQ was not. CONCLUSION: In this study population, the FTO-risk allele associates with fasting reduced fat and increased carbohydrate oxidation.