BACKGROUND AND AIM: Weight gain after stopping smoking potentially counteracts improvements in cardiometabolic risks. We investigated changes in metabolic syndrome (MetS) components and homeostasis assessment model insulin resistance (HOMA-IR) in smokers given dietary counseling during their quit attempt. METHODS AND RESULTS: Smokers (≥10 cigarettes/day) with BMI 25-40 kg/m2 were randomized to a low-carbohydrate or low-fat diet and treated with a standard course of varenicline for 12 weeks. Quitters were assessed according to the Russell standard (≤5 cigarettes after the quit date) validated with expired breath carbon monoxide (CO) < 10 ppm. Of 122 randomized participants, 108 (89%) completed clinical and laboratory assessments at 12 weeks. As changes in metabolic risk factors did not differ between dietary groups, we combined the groups to compare quitters to continuing smokers. We found similar weight change among 78 validated quitters as 30 continuing smokers (-0.1 ± 3.0 kg vs 0.3 ± 3.1 kg; p = 0.7) and change in waist circumference (-2.0 ± 3.8 cm vs -0.9 ± 3.9 cm; p = 0.2). Changes in triglyceride concentrations (-0.16 ± 0.52 mmol/l vs 0.21 ± 0.95 mmol/l; p = 0.015) and diastolic blood pressure (-0.9 ± 6 mmHg vs 1.9 ± 8 mmHg; p = 0.039) were more favorable in quitters. Changes in other cardiometabolic risks and HOMA-IR did not differ between quitters and continuous smokers, nor did energy intake or resting metabolic rate. CONCLUSION: Dyslipidemia and blood pressure improved and no early weight gain was seen in quitters, suggesting that dietary intervention can mitigate some of the effects of stopping smoking on cardiometabolic risk factors in overweight and obese smokers. CLINICAL TRIALS REGISTRATION: NCT01069458.