The GWASs on body fat percentage and fat free mass were a cross-sectional analysis of 155,961 healthy European participants from the UK Biobank. To identify genetic variation uniquely associated with body composition not confounded by illnesses and their downstream effects or metabolism-altering medication, we applied stringent exclusion criteria (e.g., psychiatric, gastrointestinal and endocrine illnesses, hormonal and antidiabetic medication). Body composition was assessed using Tanita BC-418 MA scale (Tanita Corporation, Arlington Height, IL). We included 7,794,483 genotyped and imputed SNPs and insertion-deletion variants with a MAF ≥ 1%. We covaried for assessment center, genotyping batch, smoking status, alcohol consumption, menopause, age, and socioeconomic status (measured by the Townsend Deprivation Index). We accounted for underlying population stratification by including the first six ancestry PCs, calculated on the European subsample. We used BGENIE v1.2 (https://jmarchini.org/bgenie) for sex-specific analyses and meta-analyzed these sex-specific GWASs using METAL32 (http://csg.sph.umich.edu/abecasis/metal).