Serum phosphate, BMI and Body Composition of Middle-aged and Older Adults: A Cross-sectional Association Analysis and Bi-directional Mendelian Randomization Study.

Serum phosphate was inversely associated with BMI and fat% in a population-based study of middle-aged and older adults, with a stronger effect in females than in males. Adjusting for leptin attenuated this relation in females only. MR results suggest a causal effect of BMI on phosphate but not vice versa. An underlying sex dimorphism in phosphate homeostasis should be further explored.