A study of brown fat in 286 individuals aged 20-70 found that those who were conceived in cold months have slightly higher brown fat activity, lower BMI, and lower waist circumference in both men and women of all ages.
Summary: https://www.sciencealert.com/your-body-fat-may-be-shaped-by-the-month-you-were-conceived
Original paper: https://www.nature.com/articles/s42255-025-01249-2
