Comparative effects of tea and coffee drinking on body weight in adults: a systematic review and network meta-analysis of randomised trials.

We aimed at quantifying the effects of different tea and coffee on weight loss in adults. We searched PubMed, Scopus, CENTRAL and grey literature sources to July 2024. The study excluded cross-over trials without washout period, those in critically ill patients, pregnant or breast-feeding women, multicomponent interventions and active control groups with tea or coffee. A random-effects network meta-analysis with a Bayesian framework was performed to calculate the mean difference (MD) and 95 % credible intervals (CrIs). The certainty of evidence was rated using the Grading of Recommendations Assessment, Development, and Evaluation approach, and risk of bias was assessed using Cochrane tool. Twenty-two randomised controlled trials with 1710 participants (average intervention duration = 10 weeks) were included. Green tea was effective for weight loss compared with placebo (MD: −1·23 kg, 95 % CrI: −2·45, −0·02; low certainty evidence) or water (MD: −1·61 kg, 95 % CrI: −2·90, −0·35; very low certainty evidence), while other beverages (coffee, decaffeinated coffee, green coffee, black tea and sour tea) were not. Green tea was effective for weight loss compared with water in sensitivity analysis of healthy individuals (MD: −3·31 kg, 95 % CrI: −5·83, −1·04). Based on very low to low certainty evidence, green tea drinking may result in a small weight loss in adults. This study mainly focused on weight loss effects of green tea and coffee, with limited data on other teas. Only five trials had longer intervention durations, suggesting future research on long-term effects. Most trials had high bias risk and low certainty, requiring more high-quality trials.