Weight gain and obesity rates in transgender and gender-diverse adults before and during hormone therapy

Background: Obesity rates and weight changes in adults on gender-affirming hormone therapy are lacking or limited by small sample sizes, duration, and location. Subjects/methods: This longitudinal study followed the body mass index and body weights of 470 transgender and gender-diverse adult patients (247 transfeminine and 223 transmasculine; mean age, 27.8 years) seen at a Federally Qualified Health Center and an academic endocrinology practice, both in Washington DC USA. Body weight and body mass index were recorded at baseline and at multiple follow-up clinical visits up to 57 months after the initiation of gender-affirming hormone therapy. The outcomes of this study were the changes to body weight and obesity rates following hormone therapy. Results: Within 2–4 months of starting gender-affirming hormone therapy, the mean body weight increased in the transmasculine group by 2.35 (1.15–3.55) kg and further increased beyond 34 months. Among the transfeminine group, the mean body weight was stable for the first 21 months of hormone therapy and then began to steadily increase, particularly in those under 30 years old. The prevalence of obesity at baseline was 25% in the transfeminine group and 39% in the transmasculine group. Following the initiation of hormone therapy, rates of obesity ranged from 42 to 52% among the transmasculine group and 21 to 30% among transfeminine group. Following 11–21 months of hormone therapy, weight gain ≥5 kg was seen among 21% of transfeminine individuals and 30% of transmasculine individuals. Conclusions: As compared with transfeminine individuals, transmasculine individuals have greater rates of obesity and weight gain before and during hormone therapy. Body weight and body mass index should be routinely monitored before and after the initiation of gender-affirming hormone therapy. Multidisciplinary weight-reduction interventions should be promoted where appropriate.