INTRODUCTION: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and is associated with reduced quality of life and increased healthcare utilisation. AF is increasingly recognised as a manifestation of an underlying cardiometabolic disease process, with obesity and related metabolic risk factors contributing to its development and progression. Consequently, upstream risk factor modification, including structured weight management, has emerged as a potential strategy to improve AF outcomes. While dietary and exercise interventions have been studied individually, the effectiveness of programmes combining both components has not been systematically reviewed in patients with AF who are overweight or obese. This review aims to assess the impact of combined nutritional and physical activity interventions on AF-related outcomes. METHODS AND ANALYSIS: A systematic search will be conducted in MEDLINE, CINAHL, EMBASE and EMCARE from database inception to April 2026. Eligible studies will include randomised controlled trials, quasi-experimental studies and controlled cohort studies evaluating combined dietary and physical activity interventions in adults with AF who are overweight or obese. The primary outcome will be AF symptom burden measured using validated instruments. Secondary outcomes will include quality of life, anthropometric measures, metabolic parameters and AF arrhythmia burden. Risk of bias will be assessed using RoB 2 and Risk of Bias in Non-randomised Studies of Interventions. Where appropriate, meta-analysis will be performed using random-effects models. ETHICS AND DISSEMINATION: Ethical approval is not required. Findings will be disseminated through peer-reviewed publications and scientific meetings. PROSPERO REGISTRATION NUMBER: Open Science Framework (OSF; https://doi.org/10.17605/OSF.IO/HCUZ3).