Intercross mice (Experiment 1). Body weights and adiposity index (AI) of female and male PREP wild-type (PREPWT/WT, WT), heterozygote (PREPWT/gt, H), and gene-trap (PREPgt/gt, GT) mice fed low-fat AIN-76A (LF) or high-fat (HF) diets and killed at 120 days of age. AI was calculated as (total adipose depot weight ÷ live body weight × 100). Data are presented as means ± SE. P values were calculated by ANOVA: Bonferroni correction for multiple tests sets significant P value at ≤ 0.001. Post hoc comparisons were by Tukey's HSD: means not sharing a letter are significant at P = 0.05. Genders were analyzed separately. 2-Way ANOVA. Females: body weight effect of diet, p<0.0001, effect of genotype, NS; AI effect of diet p<0.0001, effect of genotype, NS. Males: body weight effect of diet, p<0.0001, effect of genotype, p=0.0003; AI effect of diet, p<0.0001, effect of genotype, NS.