Can smoking cause obesity?

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Did you know that people living with obesity are more likely to be smokers? Let's explore the links between smoking and body weight.

Did you know that people living with obesity are more likely to smoke?

A 2018 UK study looking at more than 400,000 medical samples found that the risk of smoking rose as body mass index (BMI) increased.¹ BMI is a measure of body fat, and is the most common way of determining whether a person has obesity.
A 2010 study of 1,022 participants found that those living with severe obesity were nearly two and a half times more likely to smoke.²

With all this in mind, you might be wondering: does one cause the other? If people living with obesity are more likely to smoke, does that mean smoking can cause obesity?

The simple answer is 'probably not'. While there are links between smoking and body weight, it's unlikely that smoking would be the sole cause of weight gain.

Let's explore the facts.

What are the links between smoking and body weight?

We've seen that having a higher BMI also heightens the risk of smoking. Taken as a group, however, smokers typically have a lower BMI than the general population.²

This suggests there's a bidirectional relationship between smoking and weight gain. In other words, they both influence each other. This relationship is complicated and isn't fully understood.

Studies have suggested that:

Light smokers tend to weigh less.³
Heavy smokers tend to weigh more.³
The longer you smoke, the more likely you are to live with severe obesity.⁴

If this all seems confusing, we get it. There are many complex factors involved in the link between smoking and weight.

Some of these factors may be biological (smoking can change how fat is distributed around the body,⁴ for instance). But others likely come from social and personal factors, such as stress, financial pressure or believing that smoking helps manage weight.

In any case, it's important to know that smoking is not a healthy way to manage your weight.

Smokers might have a lower BMI than usual, but that doesn't mean that smoking directly causes weight loss. And with smoking being the largest cause of preventable deaths in England,⁵ it's simply not a gamble worth taking.

Picture of a cigarette being snapped in half.

Why are people living with obesity more likely to smoke?

Right now, we're not sure exactly why people living with obesity are more likely to smoke. However, experts have identified several potential links.

Lifestyle tendencies

Research suggests that people who smoke are more likely to engage in other risky behaviours, including eating an unhealthy diet and drinking lots of alcohol.⁶ These behaviours can also lead to weight gain.

Socioeconomic factors

These are things like income, education and job status. One study found that women in deprived communities were more likely to smoke heavily and have severe obesity.⁷

Myths about smoking and weight

It's a widely held belief that smoking helps control body weight. Some experts have suggested that heavy smokers might be less likely to quit because they worry they'll gain more weight.⁸

Addiction and the brain

There's evidence to suggest that people who smoke heavily and eat to excess may be more biologically prone to addiction.¹

Changes in body fat distribution

Studies show that smoking can change how fat is distributed around the body9 – and that smokers are more prone to having excess belly (visceral) fat.10 However, this is true for all smokers, whether or not they're overweight.

Insulin resistance

Smoking is known to increase the risk of developing insulin resistance.11 In turn, insulin resistance can make the body more likely to store fat. It's also a major risk factor for developing type 2 diabetes.

What does this all mean?

In short, it's complicated.

There may be some biological links between smoking and weight gain. However, experts have identified just as many possible causes related to non-biological factors like lifestyle and social status.

It's impossible to unpick all this and say for sure that smoking directly causes weight gain. It may be a contributing factor, but it's unlikely to ever be the only contributing factor.

Will quitting smoking make you gain weight?

It's possible. Research shows that smokers who quit gain around 4.7kg on average after 12 months of quitting.12

But remember that this is an average. Some people gain less weight. Some gain more. Others gain no weight at all.

And in any case, the weight spike often seems to be temporary. One 2018 study suggested that those who "gain a large amount early after quitting are not more likely to gain excessively after one year".13

There are many possible reasons for this tendency to gain weight. Smoking may act as an appetite suppressant, for instance, which could partially account for smokers having a lower BMI on average.

But, again, it's unlikely that smoking itself is the only cause. As with smoking and weight gain, it's all tied up in multiple complex factors – some internal, others external.

The bottom line is that potential weight gain is a very bad reason to stick with cigarettes. Smoking is associated with severe health problems and a reduced life expectancy. But quitting can quickly reduce your risk of heart disease and certain cancers, as well as boost your mental well-being.

A little temporary weight gain is a small price to pay for a happier, healthier and longer life.

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Quitting smoking might cause a small temporary weight gain. But in the long term, losing weight can be one of the most profoundly beneficial things you can do for your health.

Even a relatively small amount of weight loss (five percent to 10%) can work wonders. It can reduce your risk of heart disease and type 2 diabetes, lower your blood pressure and increase levels of 'good' cholesterol that protect heart health.

And if you're giving up smoking, too – even better!

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Sources

1. Carreras-Torres, R. et al. (2018) "Role of obesity in smoking behaviour: Mendelian randomisation study in UK Biobank" BMJ, 361:k1767 https://doi.org/10.1136/bmj.k1767

2. Chatkin, R. et al. (2010) "Smoking among morbidly obese patients" BMC Pulmonary Medicine, 10(61) https://doi.org/10.1186/1471-2466-10-61

3. Clair, C. et al. (2011) "Dose-dependent positive association between cigarette smoking, abdominal obesity and body fat: cross-sectional data from a population-based survey" BMC Public Health, 11(23) https://doi.org/10.1186/1471-2458-11-23

4. Mackay, D.F. et al. (2013) "Impact of smoking and smoking cessation on overweight and obesity: Scotland-wide, cross-sectional study on 40,036 participants" BMC Public Health, 13(348) https://doi.org/10.1186/1471-2458-13-348

5. Gateshead Health NHS Foundation Trust (2024) "Smoking is the largest preventable cause of death in England" Retrieved from https://www.gatesheadhealth.nhs.uk/news/smoking-is-the-largest-preventable-cause-of-death-in-england/

6. Lohse, T. et al. (2016) "Heavy Smoking Is More Strongly Associated with General Unhealthy Lifestyle than Obesity and Underweight" PLoS ONE, 11(2) https://doi.org/10.1371/journal.pone.0148563

7. Hart, C.L. et al. (2011) "Cause specific mortality, social position, and obesity among women who had never smoked: 28 year cohort study" BMJ, 342:d3785 https://doi.org/10.1136/bmj.d3785

8. Filozof, C. et al. (2004) "Smoking cessation and weight gain" Obesity Reviews, 5:93-103 https://doi.org/10.1111/j.1467-789X.2004.00131.x

9. Troisi, R.J. et al. (1991) "Cigarette smoking, dietary intake, and physical activity: effects on body fat distribution—the Normative Aging Study" The American Journal of Clinical Nutrition, 53(5) https://doi.org/10.1093/ajcn/53.5.1104

10. Barrett-Connor, E. & Khaw, K.T. (1989) "Cigarette smoking and increased central adiposity" Annals of Internal Medicine, 111(10) https://doi.org/10.7326/0003-4819-111-10-783

11. Willi, C. et al. (2007) "Active smoking and the risk of type 2 diabetes: a systematic review and meta-analysis" JAMA, 298(22) https://doi.org/10.1001/jama.298.22.2654

12. Aubin, H. et al. (2012) "Weight gain in smokers after quitting cigarettes: meta-analysis" BMJ, 345:e4439 https://doi.org/10.1136/bmj.e4439

13. Pankova, A. (2018) "Early weight gain after stopping smoking: a predictor of overall large weight gain? A single-site retrospective cohort study" BMJ Open, 8:e023987 https://doi.org/10.1136/bmjopen-2018-023987

This article was reviewed and approved by Lujain Alhassan, Bariatric Nutritionist, on 22 November 2025.

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