The impact of a structured weight-loss treatment on physical fitness in patients with psoriatic arthritis and obesity compared to matched controls: a prospective interventional study

OBJECTIVES: To evaluate the effects of weight loss treatment on physical fitness in patients with psoriatic arthritis (PsA) and obesity compared to matched controls. METHODS: In total, 46 patients with PsA (CASPAR) and BMI ≥ 33 kg/m(2) and 52 obese persons were included in this 12-month prospective open intervention study with a very low energy diet (640 kcal/day), followed by structured reintroduction of an energy-restricted diet and brief support for physical activity. The primary outcome was muscle strength assessed with hand-grip strength (Grippit) and leg muscle strength (timed stand test). Secondary outcomes were cardiorespiratory fitness, body composition, and physical functioning (SF-36PCS). Outcomes were assessed at baseline, 6 (M6), and 12 months (M12). Nonparametric statistics were used. RESULTS: Median weight reduction at M6 was 18.9 kg in patients and 23.0 kg in controls, (p = 0.546). At M12, patients’ median weight loss from baseline was 16.1 kg, corresponding with significant loss of total fat mass (− 30.1%), and lean mass (total − 7.0%, arm − 13.7%, and leg − 6.0%). Leg muscle strength improved in patients and controls at M6 (p < 0.001) and remained improved at M12 (p < 0.01), while hand-grip strength was unchanged in both groups. Cardiorespiratory fitness increased in controls at M6 (p = 0.018) and M12 (p = 0.028) but not in patients. Physical functioning improved in both groups at M6 (p < 0.001) and remained improved at M12 (p = 0.008) and (p < 0.01), respectively. CONCLUSION: The intervention resulted in positive effects on body weight and total body fat. Despite reduced lean body mass, the muscle strength did not deteriorate in patients with PsA and controls. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02917434, registered on September 21, 2016-retrospectively registered.