Objective To evaluate 1-year symptomatic improvement in obese patients with knee osteoarthritis (OA) on an intensive low-energy diet (LED) maintained by frequent consultations with a dietician compared to minimal attention.

Methods The LED programme consisted of group therapy with dietary consultations and two periods of a low-calorie diet of 810 kcal/day during weeks 0–8 and weeks 32–36. The control group only received dietary instruction and attention for 2 h at baseline, and at weeks 8, 32, 36 and 52. The primary end point (total Western Ontario and McMaster Universities (WOMAC) index) was assessed as the mean group difference during and after 1 year.

Results The study population consisted of 89 patients, 89% women, average age 63 years. After 1 year, mean weight loss in the LED group was −10.9 kg (11%) versus −3.6 kg (4%) in the control group (p<0.0001). There was no difference between the groups in total WOMAC index (p=0.11), although both groups improved. However, the LED intervention resulted in less WOMAC pain (7.7 mm), with a group mean difference of 7.2 mm (95% CI 1.0 to 13.4, p=0.022). After one year 14 (32.8%) responded to LED versus 7 (15.6%) to control, with an absolute benefit of 16.3% (−1.1& to 33.6%, p=0.066).

Conclusion Continuous reinforcement of a weight loss programme can be successful over a year in obese knee OA patients. Weight loss was statistically reflected only by a reduction in pain. However, the overall clinical benefits of the intervention on health should lead to a strong recommendation of weight loss in this group of patients.