Smoking cessation-related weight gain--beneficial effects on muscle mass, strength and bone health.

AIMS: To examine the effects of smoking cessation on body composition and muscle strength in comparison with continued smoking. DESIGN AND
SETTING: Twelve-month longitudinal study of adult smokers conducted in Haifa, Israel. PARTICIPANTS: Eighty-one smokers recruited from a smoking cessation programme combining group counselling and varenicline treatment. MEASUREMENTS: Measurements were taken at the beginning of the programme and after 12 months. Body composition was assessed by dual-energy X-ray absorptiometry. Muscle strength was measured by handgrip dynamometry and predicted one-repetition maximum tests. Dietary intake and physical activity levels were estimated using questionnaires. Smoking status was determined by urine cotinine. The effect of smoking cessation was assessed using univariate and multivariable linear regression analyses.
FINDINGS: Forty-one participants (age 44 ± 12 years) completed all baseline and follow-up measurements (76% continued smokers; 24% quitters). All measures of body composition and muscle strength were increased among quitters when compared with continued smokers. Adjusted differences [95% confidence interval (CI)] between quitters and smokers were: body weight 4.43 kg (1.56-7.31 kg); lean mass 1.26 kg (0.24-2.28 kg); fat mass 3.15 kg (0.91-5.39 kg); bone mineral content 48.76 g (12.06-85.54 g); bone mineral density 0.024 g/cm(2) (0.004-0.043 g/cm(2) ); handgrip strength 3.6 kg (1.12-6.08 kg); predicted one-repetition maximum of chest press 7.85 kg (1.93-13.76 kg); and predicted one-repetition maximum of leg press 17.02 kg (7.29-26.75 kg).
CONCLUSIONS: Smoking cessation is associated with weight gain mainly through accumulating extra fat, but is also associated with increased muscle mass, muscle strength and bone density.