A Cochrane review gathered evidence on pharmacological and behavioural treatments to see if they affected weight gain after giving up smoking
Most people who stop smoking gain some weight - on average about 7kg in the long term. The possibility of gaining weight often deters people from trying to quit smoking in the first place, and some who successfully stop then relapse say they did so because of increased appetite and weight gain.
There is evidence that women put on more weight than men, gaining an average of 5.2kg in the first year after giving up.
What evidence did the review find?
This review collated evidence on the effect of two types of intervention on smoking
- Interventions specifically designed to address post-cessation weight gain. The review found 11 randomised controlled trials involving adult volunteers who wanted to stop smoking and avoid weight gain. Participants smoked 20–25 cigarettes a day on average. The trials were either pharmacological or behavioural;
- Interventions not specifically designed to address post-cessation weight gain. The review found 49 studies of antidepressants, nicotine replacement therapy (NRT), varenicline and exercise. Participants were adult volunteers who smoked 20–30 cigarettes a day on average.
The success of the interventions in controlling weight gain was assessed, together with any detrimental impact that they may have had on people abstaining from smoking.
The Cochrane review discovered five pharmacological interventions that had been combined with standard smoking cessation treatments with the aim of testing their effect on post-cessation weight gain compared with smoking cessation treatments alone.
The five drugs used in the interventions were phenylpropanolamine gum, ephedrine plus caffeine, naltrexone, dexfenfluramine and fluoxetine.
All five resulted in less weight gain than controls at the end of treatment. Assessment of smoking cessation trials showed that bupropion and NRT, and probably varenicline, also reduced weight gain.
Although none of the effects of the pharmaceutical therapies appeared to be maintained one year after treatment, the evidence was insufficient to exclude a modest long-term effect for bupropion, fluoxetine and NRT.
These interventions were most effective when they were tailored to the individual. Very low calorie diets and cognitive behavioural therapy (CBT) showed the most promise in limiting weight gain; they seemed to be effective without reducing abstinence from smoking.
Both these treatments increased the success of long-term quitting but a long-term effect on weight gain was seen only with CBT. Exercise interventions were not associated with reduced weight gain at the end of treatment, but there was some evidence of worthwhile reductions over the long term.
What did the review conclude?
The evidence suggests that pharmacological interventions aimed at reducing post-cessation weight gain resulted in a significant reduction in weight gain at the end of treatment. Of all the drugs used, the reviewers believed that naltrexone showed the most promise.
However, none of the pharmacological treatments was proven to help keep weight off in the long term. As a result, none of these therapies can be recommended for providing a lasting benefit to smokers concerned about weight loss.
The long-term effect of all the interventions on weight gain related to smoking cessation is of borderline clinical relevance, at less than 1kg, compared with a typical weight gain of about 5kg for continuous abstinence over one year.
The only possible exceptions are individualised weight control interventions, CBT and very low calorie diets.
The following areas were highlighted by the Cochrane review as warranting further investigation:
- The effects of drugs that suppress appetite, such as sibutramine;
- Whether the improved smoking cessation rates associated with individualised behavioural programmes, very low calorie diets and CBT can be generalised to all smokers trying to stop, or whether the effect is specific to smokers concerned about weight gain.
The literature base for the benefit of behavioural therapies is limited.
Although single studies of CBT and very low calorie diets showed that they successfully increased abstinence and reduced weight gain in the long term, the reviewers said these findings needed to
Additionally, they said that more and larger studies of the benefits of exercise interventions were required.
The researchers also recommended that all trials of smoking cessation pharmacotherapies should assess and report weight gain, the standard deviation of any change in weight and numbers of prolonged abstinent participants.