To investigate how vulnerability to obesity in female mice is affected by increasing APOE4 allelic dosage, APOE3/3, APOE3/4, and APOE4/4 mice were fed either a control or high-fat diet (HFD) beginning at age 5 months (Week 0), which corresponds with peak ovarian cyclicity in virgin mice (Nelson et al., 1982). Here, APOE is linked to obesity due to melanocortin 4 receptor deficiency.