sunlight...

ultraviolet b stimulates the release of a-MSH from the hypothalmus.

https://pmc.ncbi.nlm.nih.gov/articles/PMC4724293/

increased a-MSH increases activity in brown adipose tissue, stimulating thermogenesis.

https://pmc.ncbi.nlm.nih.gov/articles/PMC5008654/

increased a-MSH makes social interactions more rewarding by modulating oxytosin

https://pubmed.ncbi.nlm.nih.gov/35500727/

increased a-MSH reduces appetite.

https://selfhack.com/blog/alpha-msh-its-role-in-weight-control-autoimmunity-cirs-and-cfs/

increased a-MSH produces more Eumelanin, making your skin process ultraviolet light more efficiently, making it possible to handle more sunlight exposure.