FGF21 plasma levels are higher after RYGB compared to the same weight loss induced by caloric restriction.

FGF21-signaling might thus play a role in the beneficial effects of RYGB.

Contrary to expectations, RYGB lowers body weight, fat mass, and food intake similarly in FGF21^−/− and wildtype mice.

RYGB improves glycemic control similarly in FF21-deficient and wildtype mice in a largely weight loss-dependent fashion.

FGF21 is potentially useful as adjuvant therapy in unsuccessful bariatric surgery cases.