Nutritional status was studied over a period of 13 months in 34 patients with rheumatoid arthritis (RA). Seventeen patients fasted for 7-10 days, were then transferred to a gluten-free vegan diet for 3.5 months and finally to a lactovegetarian diet for 9 months. The remaining 17 patients followed a "normal" diet. After one month, the values for body mass index (BMI) and triceps skinfold thickness (TSF) were significantly reduced in the diet group compared with the values at inclusion (p < 0.001), whereas upper arm muscle area (UAMA) was not significantly reduced. Evaluation of the whole study course revealed a significantly lower BMI (p = 0.04) and TSF (p < 0.01) in the diet group compared with the control group. The concentration of insulin-like growth factor 1 (IGF1) was significantly reduced in the diet group after one month compared with the value at inclusion (p = 0.01), but the overall difference between the two groups was not significant. There were no overall significant differences with regard to VAMA, concentration of serum albumin, haemoglobin, ferritin, zinc and copper between the two groups. Thus fast, followed by diet manipulations for one year, had a minor impact on nutritional status in patients with RA.