The long‐term effect of energy restricted diets for treating obesity

Objective To quantify the effectiveness of diet interventions by systematic review of the long‐term effects of energy restricted diets in individuals with overweight and obesity. Methods A systematic literature search was conducted for all clinical trials studying the effect of energy restricted diets on body weight in individuals with a BMI>25 kg/m2 with a follow‐up of at least 3 years and a minimum of 50 participants. Weight change from baseline and rates of loss to follow‐up at the longest follow‐up were extracted and analyzed using random‐effects models. Results Weighted mean weight loss after 3 years follow‐up was 3.5% (95% CI 0.2‐6.8%) (n = 6,163) and after 4 years follow‐up 4.5% (95% CI 4.3‐4.8%) (n = 5,696). Energy restricted diets (n = 1,433) resulted in an average 2.9% (95% CI −3.8 to −2.1%) greater weight loss compared to untreated control groups (n = 1,361). Weight regain was observed in the majority of individuals in all studies. Interpretation of the data is limited by high rates of loss to follow‐up and lack of truly untreated control groups. Conclusions On average, the long‐term effect of diets on body weight in individuals with obesity is modest, and the response is highly heterogeneous.