Males and females differ in the amounts of food and fluids they ingest. Previous studies suggest that this may be due to differences in genetic influences on intake. Gender differences in the heritability of food and fluid intake were investigated with 110 identical and 102 fraternal same-sex and 53 fraternal mixed-gender adult twin pairs who were paid to maintain 7-day food intake diaries. Linear structural modeling revealed significant genetic influences on the overall and meal intakes of foods and fluids and specific beverage and food types. No gender differences were found in the genes that influence intake or, for the most part, in the magnitude of the genetic influences on intake. However, gender differences were found for the between-meal intakes of fluids, being influenced by heredity for males but by common, familial, environment for females. The data suggest that intakes are equivalently influenced by inheritance and individual environment for both males and females and that most gender differences are due to a simple multiplicative difference between intakes possibly due to body size and/or caloric expenditure differences.