Patients with Graves disease (GD) tend to gain weight after treatment, but it remains unknown if weight gain is associated with increase in visceral and/or subcutaneous fat area (SFA,VFA). We enrolled 25 newly diagnosed GD patients (22 females, median age 33.0 years) and studied their clinical parameters and VFA, and SFA measured by a dual bioelectrical impedance analysis. We divided them into two groups based on the rates of change in the VFA and SFA, and we compared clinical parameters at the baseline between the groups to evaluate factors that influence increases in the VFA and/or SFA with treatment. The patients’ body weight (BW), VFA, and SFA were significantly increased after 6-month treatment (BW: from 54.3 ± 10.3 to 58.0 ± 11.2 kg, p<0.001; VFA: from 47.1 ± 21.3 to 54.7 ± 23.4 cm, p= 0.004; SFA: from 159.8 ± 85.9 to 182.2 ± 82.9 cm, p= 0.008). The percent changes of BW correlated with the SFA (ρ = 0.591, p= 0.002) but not with the VFA. The patients with larger VFA increases had significantly less VFA at the baseline compared to those with smaller increases: 33.9 (22.7-47.5) vs. 54.5 (45.2-64.0) cm, respectively; p= 0.011. A larger increase in the SFA was negatively associated with serum alkaline phosphatase. An increase in the SFA was associated with free triiodothyronine (T3) in a multivariate logistic analysis: odds ratio: 0.80 (0.59-0.97), p= 0.013. The patients' BW, VFA, and SFA were increased after GD treatment. The increase in SFA seemed to contribute to weight gain and was associated with a low baseline level of free T3.