Background:
Post-cessation weight gain, which has been estimated as 4-5 kilos (kg) after one year of abstinence, is a major barrier for smoking cessation.

Objectives:
To analyze the efficacy of an intervention for smoking cessation and weight gain prevention among smokers with overweight or obesity at the end of the treatment (EOT) and follow-ups in terms of rates of seven-day point prevalence abstinence, days of continuous abstinence, and weight change among quitters.

Methods:
120 smokers (MBMI=31.75; SD=4.31; 54.16% female) were randomly assigned to cognitive behavioral therapy for smoking cessation and weight gain prevention (CBT; n=60) or CBT plus contingency management for smoking cessation (CM; n=60). Individuals completed an assessment at baseline, at EOT, and at follow-up sessions (1, 3, 6, and 12 months after the EOT). Abstinence was biochemically confirmed (CO levels ≤4 ppm and cotinine levels ≤80 ng/ml), and weight was measured in kg with a calibrated medical scale. Abstinence rates were examined following the intention-to-treat analysis, and no imputation of weight missing data was performed.

Results:
Abstinence rates in the total sample were 70%, 49.17%, 37.5%, 33.33%, and 25% at EOT and 1-, 3-, 6-, and 12-month follow-ups, and mean days of continuous abstinence were 13.35±10.27, 22.22±25.10, 36.68±50.99, 54.98±86.55, and 83.51±153.44. No differences were found between groups in abstinence rates at any assessment (all p-values ≥.073) or in days of continuous abstinence (all p-values ≥ 254). Quitters gained 1.07±1.88, 2.16±3.43, 2.91±4.54, 2.92±3.43, and 3.7±4.70 kg respectively at each time point (all p-values <.001). Weight change was similar in both groups (all p-values ≥.229).

Conclusions:
Abstinence rates were higher than found in previous studies with this population. CM for smoking cessation did not improve smoking cessation outcomes at any time point. Although quitters gained weight, the increase was lower than reported in prior interventions without weight gain prevention.