Background: Weight reduction may reduce the severity of psoriasis, but little is known about the long-term effects. Objective: We aimed to investigate long-term effects of weight reduction in psoriasis. Design: We previously conducted a randomized trial (n = 60) involving patients with psoriasis who were allocated to a control group or a low-energy diet (LED) group. Here we followed the participants for an additional 48-wk period. In total, 56 patients with psoriasis [mean 6 SD body mass index (in kg/m 2 ): 34.4 6 5.3] underwent a 64-wk weight-loss program consisting of an initial 16-wk randomized phase with an LED for 8 wk and 8 wk of normal food intake combined with 2 LED products/d, followed by a 48-wk period of weight maintenance with the latter diet. After the randomization phase, the control group received the same 8 + 8-wk LED intervention, and all patients were then followed for 48 wk while on the weight-loss maintenance diet. The main outcome was the Psoriasis Area and Severity Index (PASI), and secondary outcome was the Dermatology Life Quality Index (DLQI). Results: For the present study, 56 patients were eligible, 38 agreed to participate, and 32 completed. After the 16-wk LED-only period, the mean weight loss was 215.0 kg (95% CI: 216.6, 213.4 kg), and PASI and DLQI were reduced by 22.3 (95% CI: 23.1, 21.5) and 22.3 (95% CI: 23.2, 21.4), respectively. At week 64, the mean weight loss compared with baseline was 210.1 kg (95% CI: 212.0, 28.1 kg), and PASI and DLQI were maintained at 22.9 (95% CI: 23.9, 21.9) and 21.9 (95% CI: 23.0, 20.9), respectively. Conclusion: Long-term weight loss in patients with psoriasis has long-lasting positive effects on the severity of psoriasis. This trial was registered at clinicaltrials.gov as NCT01137188.Am J Clin Nutr 2016;104:259-65.