Best practices for including sex as a variable in appetite research

Despite increasing recognition that sex is a critical variable in appetite research, many studies fail to include participants of both sexes, fail to consider reproductive physiology in participant selection, or include both sexes but fail to test for sex differences in outcomes. To help remedy this situation, this article seeks to engender enthusiasm for including sex as a variable in appetite research. We first illustrate some sex differences in healthy and disordered eating, including both male-female differences and differences across the menstrual cycle. We next provide methodological guidance for studies involving male and female participants around puberty, during reproductive adulthood, and during reproductive senescence. Studies in children ≥5 y of age should consider adrenarche and gonadarche. Appetite studies in girls and women following menarche and similarly aged males should consider the influences of sex-specific aspects the hypothalamic-pituitary-gonadal (HPG) axis function. The cyclicity of HPG function (i.e., the menstrual cycle) in girls and women presents the challenge of identifying of menstrual-cycle subphases, which are highly variable within and between individuals. Reproductive senescence refers to changes in HPG axis function that occur in both men and women beginning in mid-life. Current best practices involve consideration of hormone-assay methodology, experimental design, and statistical analyses. On the horizon are options based on wearable-sensors and nanotechnology. Well informed consideration of sex as a variable will accelerate progress in appetite research by increasing rigor, replicability, and relevance.