Weight gain after quitting smoking - how can you limit it, and what happens to your metabolism?

Weight gain after quitting smoking is common, but it varies from person to person. In a meta-analysis of clinical trials, people classified as nonsmokers at the 12-month assessment who had not used medicines to help them quit gained an average of 4.7 kg. Some lost weight, while others gained more than 10 kg (Aubin et al., BMJ 2012). Nicotine no longer suppresses appetite, the body uses slightly less energy, and it is easy to eat at times when you used to smoke. No method guarantees that your weight will stay the same. You can, however, plan meals, physical activity and ways to cope with nicotine cravings so that fear of extra weight does not undermine your decision to stop smoking.

In short

• At the 12-month assessment, participants who had not used medication weighed 4.7 kg more on average, but roughly one in six had lost weight and one in eight had gained more than 10 kg.
• Substantial weight gain was already observed in the first three months; data at successive time points came from different groups.
• Stopping nicotine does not damage your metabolism. Smoking increased energy expenditure and suppressed appetite, and both effects stop when you quit.
• Planning meals, being active and preparing for nicotine cravings make it easier to manage eating, although they do not guarantee a stable weight. Quitting smoking was associated with a lower risk of death from heart and blood vessel diseases even among people who gained weight.

Why can you gain weight after quitting smoking?

You can gain weight after quitting smoking because nicotine no longer suppresses appetite or increases energy expenditure, and eating often takes the place of cigarettes in daily routines. Some of these changes stem from nicotine's effects on the body, so gaining weight is not a sign of weak willpower.

Nicotine acts on several parts of the body, including the hypothalamus, the part of the brain that regulates hunger and fullness (Calarco and Picciotto, Nicotine & Tobacco Research 2020). The UK's NHS explains that nicotine in cigarettes suppresses appetite, which can therefore increase after quitting. The US National Cancer Institute lists increased appetite as a common withdrawal symptom (NHS, NCI). Smoking also increases energy expenditure. In a small study, 8 healthy people spent two 24-hour periods in a metabolic chamber: they did not smoke during one period and smoked 24 cigarettes during the other. On the smoking day, they used an average of 215 kcal more, or about 10%, despite eating the same food and being equally active (Hofstetter et al., NEJM 1986).

Other reasons relate to behaviour. A cigarette may have accompanied your morning coffee, a break at work or a stressful moment. Without it, it is easy to fill the break with a chocolate bar or a sweetened coffee, even when hunger is not the issue. The NHS also notes that taste and smell improve after 48 hours without cigarettes, so food may taste better.

How much weight can you gain, and when does it increase fastest?

Average weight gain without medication was 2.9 kg after 3 months and 4.7 kg after a year. The meta-analysis included 62 clinical trials, which used different definitions of abstinence.

These results come from different studies and groups of participants who did not use medication; they do not track weight changes in a single group.

The average does not show how much the results varied. The authors estimated that after a year, 16% of people had lost weight, 37% had gained less than 5 kg, 34% had gained between 5 and 10 kg, and 13% had gained more than 10 kg. Similar results were found among people using medication to help them quit and among those particularly worried about weight gain. These figures describe clinical trial participants and cannot predict how much weight an individual will gain.

What happens to your metabolism when you stop nicotine?

Stopping nicotine does not damage your metabolism. Your body uses less energy than when you smoked, and nicotine no longer suppresses your appetite, so it is easier to gain weight while eating the same amount.

In the study by Hofstetter and colleagues, smoking increased total energy expenditure over 24 hours but did not change the basal metabolic rate, meaning the energy used at rest. Some researchers suggest that weight gain after quitting represents a return to the weight typical of a nonsmoker (Calarco and Picciotto 2020). This remains a hypothesis.

When asking when metabolism returns to normal, it helps to consider withdrawal symptoms, appetite and body weight separately:

The studies we reviewed do not give a single time at which metabolism returns to normal. They do not confirm timelines found online, such as 2 weeks, 3 months or 2 years.

How can you limit weight gain after quitting smoking?

To limit weight gain after quitting smoking, it helps to plan meals, decide what to do when nicotine cravings strike, choose drinks with fewer calories and move more. This does not guarantee a stable weight, but it lets you manage the factors that depend on daily habits.

Cochrane reviews bring together clinical trials on a particular topic and assess them using consistent methods. A 2021 review examined ways to prevent weight gain after quitting smoking. For none of them was there sufficiently certain evidence of a reduction in weight gain over the longer term that would make a practical difference (Hartmann-Boyce et al., Cochrane 2021). The available studies cannot reliably establish how much these methods help over time. Changes to eating and physical activity still make sense, preferably as a few specific steps that fit your day.

Plan meals to avoid unplanned eating

Hunger is easier to manage when meals are prepared in advance and eaten at similar times. There is no single number of meals that suits everyone: a shift worker will organise their day differently from someone who works from home. A meal with vegetables, a protein source (eggs, fish, dairy products or pulses) and grains, rice or wholemeal bread usually keeps you full for longer. Bringing lunch or sandwiches from home means you do not need to buy food from a vending machine when your old cigarette break comes around.

What if you mistake a cigarette craving for hunger?

According to the NHS, a strong urge to smoke lasts up to 15 minutes. During that time, you can take a short walk, drink water or unsweetened tea, brush your teeth or keep your hands busy. If you are hungry, it is better to eat a portion you have planned in advance, such as a piece of fruit, plain yoghurt or a few nuts, than to snack from an open packet. Eating every time you want a cigarette, however, simply replaces one habit with another.

Calories in drinks and alcohol

It is easier to overlook calories you drink than calories you eat. Sweetened drinks, juice and coffee with syrup provide energy but do not keep you full for long. Replacing them with water, tea or coffee without sugar reduces calorie intake without changing your meals. Alcohol presents two difficulties: it contains plenty of calories, and the National Cancer Institute notes that many people are used to smoking while drinking beer, wine or cocktails.

Physical activity that suits your abilities

The same Cochrane review found no clear effect of exercise programmes on weight gain at the end of the programme. After 12 months, average weight gain was about 2 kg lower than in comparison groups; this finding from 3 studies involving 182 people was based on evidence of low certainty. You do not need to start with intense exercise. A 10-minute walk during your former cigarette break or taking the stairs instead of the lift can be a starting point. As your fitness improves, it becomes easier to exercise for longer. People with heart, lung or joint conditions should agree on suitable activity with a doctor.

Sleep, stress and support from people close to you

Insomnia, irritability and anxiety are among the withdrawal symptoms that are strongest in the first few weeks (Hughes 2007). When you are tired and stressed, it is easier to reach for a cigarette or food. Going to bed at a regular time and easing tension through conversation, a walk or a few minutes of calm breathing can help. People close to you can support you by not smoking around you, offering cigarettes or sweets, or commenting on every change in your weight.

How often should you weigh yourself after quitting smoking?

Body weight varies from day to day, for example because of the amount of water in your body, so a single reading tells you little. It is better to weigh yourself less often, such as once a week at the same time, and look at the trend over several weeks. A higher reading does not undo your success in quitting smoking. One measurement does not explain the cause of a change; the trend over several weeks matters more.

What should you do if you have already gained weight after quitting?

If you have already gained weight after quitting smoking, first take time to work out why. Going without food to lose weight is not a good idea, especially during the first few weeks when staying away from cigarettes is already difficult.

A few questions can help: how many kilograms have you gained, and over what period? When is your appetite strongest? What has replaced cigarettes? Are you less active during the day, and have your medicines changed?

There are two reasons to discuss your medicines with a doctor. Some medicines can themselves contribute to weight gain. In addition, components of tobacco smoke speed up the breakdown of certain medicines in the liver, including clozapine, olanzapine and theophylline. After quitting smoking, their concentrations can rise within just a few days, even in people using nicotine patches. If you take these medicines, discuss your plan to stop smoking with your doctor. If you take clozapine, you need to contact a specialist urgently, because reducing or stopping smoking can substantially increase the drug concentration. A doctor must decide on monitoring and any dose adjustment (NHS Specialist Pharmacy Service).

Not all weight gain is caused by quitting smoking. Age, changes in working patterns, menopause and certain conditions, such as an underactive thyroid, also affect weight. If the increase is substantial, a doctor will therefore check for other causes too. You do not need to wait until withdrawal symptoms pass before changing your eating habits and physical activity. In three US cohort studies, which followed large groups of people over many years, the risk of type 2 diabetes was temporarily higher among people who had quit smoking 2-6 years earlier than among those still smoking. The risk rose with the amount of weight gained and was not higher among people who had not gained weight (Hu et al., NEJM 2018).

Does treatment for nicotine dependence help with weight control?

Treatment for nicotine dependence primarily helps you stay smoke-free. Some medicines used in this treatment slightly reduce weight gain while you take them, but studies do not confirm that they prevent weight gain over the longer term.

In the Cochrane review, nicotine replacement therapy, such as nicotine patches or gum, reduced weight gain by an average of about 0.5 kg at the end of treatment; the result at 12 months was too imprecise to assess a lasting effect. With bupropion, the difference at the end of treatment was about 1 kg, and no benefit was demonstrated after a year. The difference with varenicline was very small. Nicotine is therefore not a weight-loss aid, and medicines for dependence are not a way to maintain your weight. They ease nicotine cravings and withdrawal symptoms, while an addiction therapist can help you plan for situations in which the urge to eat replaces the urge to smoke.

If fear of weight gain makes it hard to stay away from cigarettes, mention it at your first appointment. Treatment for nicotine dependence at Nasz Gabinet starts with a consultation covering your smoking history, previous attempts to quit, medical conditions and medicines. Obesity medicines are not routinely used in people quitting smoking solely to prevent weight gain.

When should you speak to a doctor, dietitian or psychologist?

Seek professional help if fear of weight gain makes you consider smoking again, if you have episodes of binge eating, or if your weight continues to rise substantially despite changes to eating and physical activity. You also need to speak to a doctor if you had obesity or a chronic condition, such as diabetes or high blood pressure, before quitting smoking.

• A doctor looks for the causes of weight gain, assesses medical conditions and medicines, orders tests and treats nicotine dependence. If you have obesity, the doctor may suggest treatment for it, including medication when indicated.
• A dietitian adapts your eating plan to your daily routine, preferences and health.
• A psychologist or therapist helps when you use food to cope with stress, boredom or nicotine cravings, and with episodes of binge eating.

If you are carrying excess weight, a doctor will assess whether you need obesity treatment. At Nasz Gabinet, this combines medical care, a dietitian's eating plan and work on emotional eating. Not everyone who quits smoking needs this treatment.

See a doctor without delay if your weight rises quickly despite no change in your eating habits, especially if you develop swelling in your legs, breathlessness, marked weakness or other new symptoms. An illness may be responsible, rather than quitting smoking. This article does not replace a medical consultation.

Frequently asked questions

Does everyone gain weight after quitting smoking?

Not everyone gains weight after quitting smoking. In the group that did not use medication, average weight gain after 12 months was 4.7 kg, and an estimated 16% lost weight. Results were similar among people who worried about weight gain and those who did not.

How long does increased appetite last after quitting smoking?

It is not known exactly how long increased appetite lasts after quitting smoking, because studies do not identify a single timeframe. Withdrawal symptoms are strongest in the first week and usually ease within a month, while substantial weight gain was already observed in the first 3 months. If your appetite is still much greater than before quitting after several months, discuss it with a doctor or dietitian.

Can you quit smoking and try to lose weight at the same time?

You can quit smoking and try to lose weight at the same time if changes to your eating habits are moderate and introduced gradually. A 2021 review did not find sufficiently certain evidence that measures to limit weight gain reduce the chance of quitting smoking. In two studies, participants who received only detailed weight-loss information without an individual plan were less likely to quit smoking (the certainty of this evidence was low or very low). People with obesity or a chronic condition should agree on a plan with a doctor.

Do nicotine patches or gum prevent weight gain?

There is no certain evidence that nicotine patches and gum prevent weight gain over the longer term. In a 2021 review, they reduced weight gain by an average of about half a kilogram at the end of treatment, while the effect after a year was uncertain. They do ease nicotine cravings and withdrawal symptoms. It is best to discuss how to use them with a specialist, and to read the leaflet if buying them without a prescription.

Will smoking again help you lose weight?

Returning to smoking is not a way to lose weight. In US cohort studies, people who quit smoking and gained more than 10 kg had a lower risk of death from heart and blood vessel diseases than those who continued smoking (Hu et al., NEJM 2018). We discuss the effect of smoking on life expectancy in our article on how long the average smoker lives. If worries about weight make you want a cigarette, seek help with treating dependence and planning your meals.

Sources

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