When people give up smoking they usually put on from 4 to 5 kg (9 to 11 lbs) within 12 months, much more than previously thought, researchers from INSERM, France, and the University of Birmingham, UK, reported in the BMJ (British Medical Journal). The authors added that most of the weight gain tends to occur within three months of quitting.

The researchers stress that although more weight is gained after quitting smoking than previously thought, the benefits of not smoking anymore far outweigh any of the possible harms associated with putting on some pounds – their findings should in no way discourage people from giving up the habit.

Professor Henri-Jean Aubin and team explained that we have known for a long time that quitting smoking is associated with weight gain, although estimates have often varied.

Weight gain has always been a major concern for a considerable number of people, especially adult females, when considering whether to give up smoking.

In this study, the team set out to determine what impact smoking cessation might have on the body weight of successful quitters. They gathered data from 62 different studies which focused on weight gain among people who managed to stop smoking without any type of NRT (nicotine replacement therapy) within 12 months of giving up.

They found that successful quitters without the aid of NRT:

  • Gained an average weight of 1.1 kg in the first month
  • Gained 2.3 kg in two months
  • Gained 2.9 kg in three months
  • Gained 4.2 kg in six months
  • Gained 4.7 kg in a year

Most smoking cessation advice leaflets that public health authorities give out to people quote an average weight gain of 2.9 kg, a lot less than the average worked out from the 62 studies revealed.

According to previous studies, the average woman is willing to tolerate a weight gain of 2.3 kg after giving up smoking, but not more.

The authors explained that they found considerable variations in body weight amongst those that have given up smoking after one year.

While 13% of successful quitters gain more than 10 kg after 12 months of being smoke-free, about 16% actually lost weight.

The researchers emphasize that the average value does not reflect the actual weight change of many people who stop smoking.

Nicotine replacement therapy is often chosen by smokers who are thinking of giving up, because they believe they will not put on so much weight, compared to quitting “cold turkey“. However, the researchers found that weight gain estimates in those who used NRTs proved similar.

Examples of NRT include a transdermal patch for the administration of nicotine, nicotine sprays, nicotine sublingual tablets, nicotine lozenges, nicotine inhalers, and nicotine gum. Some consider snus and nasal snuff as NRTs, however, they cause some negative health effects.

The average amount of weight people put on after they give up smoking has been underestimated, the authors wrote.

In an Abstract in the same journal, they wrote:

“Smoking cessation is associated with a mean increase of 4-5 kg in body weight after 12 months of abstinence, and most weight gain occurs within three months of quitting.

Variation in weight change is large, with about 16% of quitters losing weight and 13% gaining more than 10 kg.”

They added that perhaps doctors should provide patients with a range of expected weight gains.

Further studies are needed to identify which people have the greatest risk of gaining the most weight, and to clarify the best way to prevent continued weight gain once a person has decided to stop.

Spanish and Australian experts from Sydney University and the Catalan Institute of Oncology/University in Barcelona wrote in a linked editorial that more data is required to provide clear evidence.

They absolutely agree that the risk of gaining weight should not put people off quitting smoking, because the benefits from giving up far outweigh the risks from weight gain.

The authors highlight that according to earlier research, many smokers gain more weight compared with those who never smoked for a few years. However, after a few years the rate of weight gain falls compared with those who have never smoked.

They conclude writing:

“Although obesity is positively associated with an increased risk of all cause mortality, cohort studies indicate that modest weight gain does not increase the risk of death; smoking does.”

Written by Petra Rattue