A systematic review and meta-analysis of randomised controlled trials examining the effect of ultra-processed food on energy intake and weight gain

Ultra-processed food (UPF) may contribute to increased energy intake and weight gain, but evidence synthesis from randomised controlled trials (RCT) is lacking. A pre-registered systematic review and meta-analysis of RCTs was conducted comparing UPF with less processed food (LPF) on energy intake and/or body weight in humans. Secondary analyses (meta-regression and sub-group) examined effects of UPF on appetite sensations, eating rate, palatability and considered the role of nutrient profile in explaining results. Ten eligible studies were included. UPF trial arms tended to have higher energy intake (standardised mean differences [SMDs]=0.18-0.44), but statistical significance varied between analytic models. Weight gain (SMD=0.65) and eating rate (SMD=0.96) were significantly greater in UPF trial arms. No significant differences in palatability, appetite sensations or energy intake later in the day were observed. Diets (UPF vs. LPF) used in trials were not matched for nutrient profile. Effects on energy intake varied if UPFs were higher (SMD=0.71) or similar (SMD=0.02) in energy density. Current RCTs are suggestive that UPFs may increase energy intake and body weight; however, results may be explained by energy density of foods used. Further research is needed to understand whether the level of processing impacts health outcomes independent to nutrient profile.