BACKGROUND: Observational studies showed that exercise might reduce nicotine craving and enhances mood when quitting smoking. Furthermore, increasing exercise might help to prevent or minimize weight gain through energy expenditures. We aimed to test the following hypothesis through a randomized controlled trial of sedentary adult smokers: including a moderate-intensity physical activity intervention in a smoking cessation program increases the chances of quitting and reduces nicotine withdrawal symptoms, negative mood, stress, desire to smoke and weight gain in smokers recruited from the community.