Ramadan is the Islamic tradition of fasting for one month from sunrise to sunset. Generally, Ramadan is known to impact weight. This systematic review and meta-analysis specifically evaluated the effects of Ramadan on both weight and body mass (fat mass and fat-free mass), pre and post fasting, and in the context of there being no attempt to influence physical activity or diet. The meta-analysis was conducted on 70 publications, 90 comparison groups and 2947 participants. Data was also extracted for diverse sub-groups such as overweight/obese, gender and geographical location. The results showed that Ramadan promoted a significant reduction in weight pre and post fasting across all participants, and that the greater the BMI prior to Ramadan fasting, the greater the weight loss. No significant differences were noted between genders. Weight loss was significant in the Middle East + North Africa, South Asia and South East Asia, but not in Westernized countries. Ramadan fasting promoted a transient reduction in fat mass as a percentage of weight, and absolute fat mass, but quickly returned to pre-fasting levels at follow-up 2-5 weeks later. A significant reduction in fat-free mass was also noted but 30% less than total fat mass. There was insufficient data to analysis the possible impact of physical activity. The authors conclude that Ramadan represents an opportunity for promoting weight and fat loss for people with overweight or obesity but requires strategies for long-term maintenance