The FTO gene (rs9939609) has been associated with greater food intake and adiposity in adults. Likewise, literature suggests that copies of the ‘A’ allele of the FTO gene may be associated with increased intake in children. The purpose of this study was to assess the impact of FTO on healthy, non-overweight children’s eating during an ad libitum single-item snack task.


Participants were healthy, 5-10 year old children, between the 15th and 95th percentile for BMI, who provided saliva samples for genetic analyses. Children had nothing to eat or drink for 90 minutes prior to participation in an ad libitum snack task in which they were provided 200 g of M&M® candy and instructed “You can eat as much or as little as you like,” while watching a brief cartoon with neutral content. Data were analyzed using ANCOVAs to examine differences in total calories (kcal) consumed by genotype.


One hundred and forty-nine children (53% male) provided samples for genetic analyses. Twenty-eight were homozygous for the obesity-risk allele (AA), 70 were heterozygous (AT), and 51 were wild type (TT). Mean age and BMI-z score were not significantly different by genotype: 8.2±1.4 y.o. and 0.5±0.9 for AA, 8.5±1.6 y.o. and 0.3±1.0 for AT, and 7.9±1.4 y.o. and 0.2±1.0 for TT. Both BMI z-score (p=0.02) and age (p=0.01) were positively correlated with kcal intake. Controlling for BMI z-score and age, no relationship was found between genotype and kcal consumption (p=0.56).


Contrary to expectation, FTO status was not associated with increased kcal consumption during the ad libitum snack task. It is possible that the increased intake reported to be associated with FTO status is magnified in the presence of food choice (e.g., variety), and is more difficult to detect using the single-item paradigm.