It is common for athletes in weight category sports to try to gain a theoretical advantage by competing in weight divisions that are lower than their day-to-day body mass (BM). Weight loss is achieved not only through chronic strategies (body fat losses) but also through acute manipulations prior to weigh-in (“making weight”). Both have performance implications. In this review we focus on Olympic combat sports, noting that the varied nature of regulations surrounding the weigh-in procedures, weight requirements and recovery opportunities among these sports provide opportunity for a wider discussion of factors that can be applied to other weight category sports. We summarise previous literature that has examined the performance effects of “weight making” practices before investigating the physiological nature of these BM losses. Practical recommendations in the form of a decision tree are provided to guide the achievement of acute BM loss while minimising performance decrements.