Modest exercise increase can curb weight gain after quitting smoking

For middle-aged women who worry about adding on kilogrmmes when they quit smoking, a large study suggests that adding even a modest amount of weekly exercise after quitting can minimize weight gain. 

Nearly 7 of 10 US adult cigarette smokers say they want to quit, according to the Centres for Disease Control and Prevention. The fear of gaining weight discourages many of them. 

“We found even a little bit of physical activity minimised weight gain after women stopped smoking,” study leader Juhua Luo of the School of Public Health at Indiana University in Bloomington told Reuters Health by phone. 

Even walking for a weekly total of about 90 minutes at five kilometres per hour was enough to minimise weight gain after smoking cessation, Juhua said. The best results were seen when women engaged in 150 minutes of moderate intensity activity per week. 

Surprisingly, “women who had low physical activity and then transitioned to increased physical activity after they quit smoking had the same weight benefit as women who were physically active before and after they quit smoking”, she said. 

For three years, the study team tracked 4,717 smokers, ages 50 to 70, who were participating in the long-term Women’s Health Initiative study. The 2,282 women who quit smoking gained an overall average of 3.5 kilogrammes. 

The researchers gauged weekly physical activity levels by the type of activity, how intense or strenuous it was, and how long and how frequently a woman exercised to derive a value in so-called metabolic equivalents of task (MET). For example, one hour of moderate-intensity activities such as biking, easy swimming, folk dancing or using an exercise machine was valued at five METs. High-intensity exercise like aerobics was seven METs and low-intensity activity such as bowling, golf or walking at average speed counted as three METs. 

Quitters who increased their levels of physical activity by 15 MET-hours per week or more, about the equivalent of 150 minutes of moderate-to-intense exercise, gained an average of 2.55kg while those who did no exercise or decreased their activity gained an average 3.88kg. 

Women with a high level of physical activity at the beginning and the end of the study also had low weight gain after quitting smoking, averaging an increase of 2.63kg. 

Increasing physical activity had a stronger beneficial association for women who were obese compared with normal weight women, the researchers found. The association between physical activity and weight gain also appeared slightly stronger for younger women, the study team reports in the journal Menopause. 

“My hope is that women believe this study and it will convince them that stopping smoking doesn’t have to lead to weight gain,” said Dr JoAnn Pinkerton of the University of Virginia, Charlottesville, who is also executive director of the North American Menopause Society. 

“Hopefully they will start an exercise programme and watch their diet when they stop smoking,” Pinkerton, who was not involved in the study, said in a phone interview. 

“There’s no clear gender difference in gaining weight after smoking cessation. I wish there had been men in the study to make it more comprehensive. Weight gain is equally important to men,” noted Dr Qi Sun of the Harvard T.H. Chan School of Public Health in Boston, who was not involved in the study. 

Although the study excluded women over 70, Pinkerton added, “stopping smoking is beneficial to women at any age”.