Effectiveness of combined nutrition and exercise interventions on body weight, lean mass, and fat mass in adults diagnosed with cancer: a systematic review and meta-analysis.

Context: Changes in body weight and composition (fat and lean mass) are prominent side effects of cancer treatment. Nutrition and exercise interventions are both key strategies to protect against these adverse effects, yet their impact when combined has not been comprehensively reviewed in adults with cancer.
Objective: This systematic review and meta-analysis aims to assess the effects of combined nutrition and exercise interventions on body weight and composition in adults with cancer.
Data Sources: Four databases were searched until January 2021. Combined nutrition and exercise randomized controlled trials that detailed the nutrition and exercise prescription and reported body weight and composition outcomes were eligible.
Data Extraction: Risk of bias was assessed through the Cochrane Collaboration tool. The number of participants, mean values, and standard deviations of the outcome variables were extracted. Mean differences (MDs) were pooled using random-effects models. Predetermined subgroup analyses included cancer type, intervention intent, exercise modality, and use of behavior change strategies.
Data Analysis: Twenty-three RCTs were included. Nutrition plus exercise interventions significantly reduced body weight (MD -  2.13 kg; 95%CI, - 3.07 to - 1.19), fat mass (MD - 2.06 kg; 95%CI, - 3.02 to - 1.09), and lean mass (MD - 0.43; 95%CI, - 0.82 to - 0.04). Subgroup analyses in women with breast cancer showed that weight loss interventions and interventions incorporating behavior change strategies significantly reduced body weight and fat mass but also reduced lean mass. Interventions aiming to maintain body weight showed no changes in body weight, as intended.
Conclusion: Combined nutrition and exercise interventions successfully reduce body weight and fat mass in adults with cancer but also reduce lean mass. In contrast, weight loss-focused interventions are associated mostly with reduced lean mass.
Systematic Review Registration: PROSPERO registration number CRD42020161805.
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