About 80% of smokers who stop smoking gain weight after they stop; on average 5 kg in the first year and about 6 to 7 kg overall. However, weight gain varies a lot between individuals, with some putting on 10 kg or more in a year. Although some factors predict who will gain excessive weight, they are not clinically useful for targeting individuals at high risk. Instead, it may be prudent to monitor weight gain after cessation and intervene with people gaining more than 1 kg/month. There is some evidence that weight gain after cessation can be prevented by dietary intervention that includes setting an energy intake goal and regular monitoring of weight and adjustment of energy intake. However, there are fears that such an approach may harm the success of a quit attempt because it may worsen craving for cigarettes. There is no evidence that this is the case, but the data are too imprecise to be completely reassuring. Exercise programs may reduce cravings for tobacco and increase the likelihood of achieving smoking abstinence, and there is some evidence that they reduce weight gain in the longer term. Consequently, they may be safely recommended but the effect on weight gain is modest. Long‑term nicotine replacement therapy prevents several kilograms of weight gain but it may produce harmful metabolic changes that increase cardiovascular risk. Randomized trials are needed to assess efficacy. Thus, weight gain after cessation remains problematic with few interventions to prevent it that have only modest effectiveness.