This systematic review synthesized the qualitative evidence from the peer-reviewed literature on factors influencing obesogenic behaviours in adolescent girls (age 10-19) and women of reproductive age (15-49 years of age) in low- and middle-income countries (LMICs). The review included 71 studies from 27 different countries; about half of the studies focused on dietary behaviors, 17 on physical activity and 22 on diet and physical activity. Gender norms and perceived lack of importance of healthy behaviours across the life cycle were important factors. Ubiquity of cheap, unhealthy food, food safety concerns, taste preferences and social desirability of foods drive consumption of unhealthy foods, while busy lives and limited exercise spaces keep girls and women from being physically active. Obesogenic behaviours are influenced by factors at multiple levels (individual, social, physical and environmental) and require diverse solutions to address these factors in LMICs.