Here we will analyze the longitudinal family data of the Framingham Heart Study [5] provided for Genetic Analysis Workshop 16, by evaluating associations between weight, BMI, and single-nucleotide polymorphisms (SNPs) on FTO (rs1121980, rs9939609) or near MC4R (rs17782313, rs17700633), which were recently identified to be consistently associated with obesity-related measures through cross-sectional genome-wide association studies [1,4]. The gene discussed is MC4R; the disease is Obesity.