It has been hypothesized that metformin inhibits food intake, but in humans such effect needs to be demonstrated. Our study aims at investigating the effect of metformin administration on food intake in obese, non‐diabetic, normotensive patients.

Thirty patients underwent a double‐blind, randomized study. Placebo (P; n = 15) and metformin (M; n = 15) were both given for 15 days, and food intake (FI) was recorded at baseline and in the last 4 days of each treatment period.

M administration allowed a stronger decline in body weight (BW) (−2.8 ± 1.6 vs. −0.3 ± 0.4 kg P < 0.01), body fat (BF) (−1.4 ± 1.2 vs. −0.3 ± 1.1 kg P < 0.01), plasma leptin concentration (−5.2 ± 8.9 vs. −1.8 ± 10.4 ng mL⁻¹P < 0.05) and FI (−642 ± 491 vs. −70 ± 1165 kJ per 24 h P < 0.01) than P. In M‐treated subjects, changes in FI significantly correlated with those in BW (r = 0.63, P < 0.007) and BF (r = 0.74, P < 0.001). Independently of sex and change in BF, the changes in FI and in fasting plasma leptin concentration (r = 0.58, P < 0.01) were still correlated.

Our study suggests that metformin administration is useful to inhibit FI and to lower BW and BF in obese non‐diabetic patients.