Effect of Dietary Interventions on Body Weight, Body Composition and Cardiovascular Risk Factors After Varenicline-assisted Smoking Cessation : A Randomized Controlled Trial

Summary Introduction: Cigarette smoking is a major risk factor for the development of many lifestyle diseases, including cardiovascular disease. Overweight and obesity have also been shown to be associated with an increased risk for several lifestyle diseases, and co-occurrence of overweight and smoking has substantial consequences for health. Smoking cessation and weight reduction are associated with both immediate and long-term benefits including reduced risk of cardiovascular disease and increased life expectancy. Varenicline is an approved smoking cessation product shown to increase the chances of a successful attempt to quit smoking. However, smoking cessation is associated with weight gain, and it is suggested that this weight gain may offset some of the advantages of giving up smoking. Concern regarding post cessation weight gain seems to be a powerful motivator for continued smoking, and post cessation weight gain is also often the reason for relapsing after cessation. It is therefore necessary to find some interventions that may prevent, or at least reduce, the weight gain associated with smoking cessation so that a larger proportion of weight concerned smokers may successfully quit smoking. Aims: The first aim of this thesis was to compare the efficacy of a low fat diet high in complex carbohydrates (LFHCC; ≤30 energy % fat, ≤20 energy % protein and ≥50 energy % carbohydrate) and a high protein diet moderately reduced in carbohydrates (HPMRC; ≥25 energy % protein, ≤55 energy % fat and ≤20 energy % carbohydrates) in preventing short-term weight gain four and 12 weeks after smoking cessation. The second and third aims were to compare the effects of the two diets on body composition and cardiovascular risk factors, respectively, 12 weeks after smoking cessation. The last aim was to compare dietary changes and examine correlations between the dietary changes and changes in body weight four weeks after smoking cessation. Subjects and methods: A total of 80 healthy overweight or obese men and women who were smoking ≥ 10 cigarettes daily and willing to take varenicline were randomized. Mean age was 50 (SD 9) years and mean BMI was 31 (SD 4) kg/m2. Both groups received individual counseling for diet and smoking cessation with a total of 12 visits, the first visit at the date of screening and the last visit 12 weeks after smoking cessation. Continuous abstinence rates were estimated based on self-reported smoking status, confirmed by CO-measurements at every visit. Body weight was measured every week. Body composition (waist circumference, hip circumference, waist-to-hip ratio, body fat % and muscle mass in kg) and cardiovascular risk factors (blood pressure, fasting blood glucose, total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides) were measured at randomization and 12 weeks after smoking cessation. For measuring of compliance with the intervention diets, 7-days weighed records were conducted at randomization and four weeks after smoking cessation. Statistical analyses were performed twice; once for the participants who were abstinent from smoking all 12 weeks after smoking cessation, and once for all completers regardless of their smoking status. Results: A total of 70 participants met at the last visit, with no difference in completion-rates between the intervention groups. Of the participants randomized, 37.5% managed to be abstinent from cigarette smoking all twelve weeks after smoking cessation, with no significant difference between the dietary intervention groups. Four weeks after smoking cessation the change in body weight was not different between the groups (p>.05), but the HPMRC group had a significant (p.05). However, both groups showed an increase in HDL (p<.05). Among all completers, we found mean between-group differences in waist circumference reduction (2.3 cm [95% CI .2, 4.4], p=.03), fat mass (1.6 kg [95% CI .3, 2.9], p=.02) and triglycerides (.32 mmol/L [95% CI .03, .62], p=.03), all in favor of the HPMRC group. Both groups made several significant changes to their dietary composition, but no significant between-group difference in reduction of energy intake. The LFHCC group significantly reduced their intake of fat to ≤ 30 E% while the HPMRC group significantly increased their protein intake to ≥ 25 E%, but neither of the intervention groups met the target level for intake of carbohydrates. Despite this, we found a significant correlation between the change in intake of carbohydrate and change in body weight (r=.51, p=.02) in the HPMRC group among the nonsmokers. When we included the reduced smokers we found a significant correlation between changes in intake of protein and fat and changes in body weight (r=.39, p=.01 and r=.36, p=.02, respectively) in the HPMRC group. Conclusion: Both a moderately energy-reduced diet with decreased intake of fat and increased intake of complex carbohydrate and a moderately energy-reduced diet with increased intake of protein and reduced intake of carbohydrates prevented short-term post cessation weight gain. However, it seems like a diet with increased intake of protein and reduced intake of carbohydrate may result in more beneficial effects, such as decreased body fat, abdominal fat (waist circumference) and triglyceride levels compared to a diet with decreased intake of fat and increased intake of carbohydrate