Quitting Smoking Without the 5 Kilos: What GLP-1 Research Shows About Nicotine, Cravings, and Post-Quit Weight Gain
The average quitter puts on nearly 5 kg in the first year, and the fear of that number keeps plenty of people smoking. Two randomised trials have now tested GLP-1 drugs during a quit attempt. Here is what they found, where they disagree, and what it means for a low-dose protocol.
4.7 kg
AVERAGE WEIGHT GAIN 12 MONTHS AFTER QUITTING WITHOUT MEDICATION (AUBIN, BMJ 2012)
46%
ABSTINENCE AT 6 WEEKS ON EXENATIDE PLUS NICOTINE PATCH, VERSUS 27% ON PATCH ALONE (YAMMINE 2021)
~50%
LOWER CARDIOVASCULAR RISK IN RECENT QUITTERS THAN SMOKERS, DESPITE WEIGHT GAIN (CLAIR, JAMA 2013)
A 44-year-old nurse has quit smoking three times. Each attempt lasted about ten weeks. Each time, her jeans stopped fitting around week six, she started eating toast with honey at 11 p.m. to fill the gap where the last cigarette of the night used to be, and by week ten she decided that smoking was the lesser evil. She is not unusual. Concern about weight gain is one of the most commonly reported reasons smokers, especially women, put off quitting or relapse after they do.
GLP-1 receptor agonists act on appetite and on the brain's reward circuitry, which makes them an obvious candidate for this problem. Researchers have now run two randomised trials of GLP-1 drugs in people trying to quit, plus a large observational study of semaglutide users. The results are useful, and they are less tidy than headlines suggest.
This article covers how much weight quitters actually gain and why, what the GLP-1 cessation trials showed, how these drugs sit alongside varenicline, bupropion, and nicotine replacement, a drug-metabolism change after quitting that catches many people out, and how a low-dose protocol might be timed around a quit date.
Key takeaways
- •People who quit smoking without medication gain an average of 4.7 kg by 12 months, most of it in the first three months, according to a 2012 BMJ meta-analysis of 62 studies. About 13 percent gain more than 10 kg.
- •In a 2021 randomised trial of 84 smokers, exenatide 2 mg weekly plus a nicotine patch produced 46 percent abstinence at six weeks against 27 percent for patch plus placebo, with less weight gain among quitters.
- •A 2023 trial of 255 smokers found that adding dulaglutide to varenicline did not raise quit rates, but participants on dulaglutide lost weight while those on placebo gained it.
- •Quitting still wins on health even with weight gain. Recent quitters in the Framingham Offspring cohort had roughly half the cardiovascular risk of people who kept smoking.
- •Quitting removes the smoke-driven boost to the liver enzyme CYP1A2, so caffeine levels can roughly double within weeks. That jitteriness is often mistaken for nicotine withdrawal.
How much weight do people gain after quitting smoking?
People who quit smoking without cessation medication gain an average of about 4.7 kg (10 lb) over the following year. That figure comes from a meta-analysis of 62 studies published in the BMJ in 2012 by Aubin and colleagues. The gain is front-loaded: about 1.1 kg in the first month, 2.9 kg by month three, and 4.2 kg by month six, after which the curve flattens.
The average hides a wide range. In the same analysis, around 16 percent of abstinent quitters actually lost weight over 12 months, and around 13 percent gained more than 10 kg. That spread matters for planning, because the people most anxious about weight gain are often the ones with a history of gaining the most. Older guidance that told smokers to expect "2 or 3 kg" underestimated the typical gain by about half.
Mean weight gain after quitting smoking, kg
Untreated quitters who stayed abstinent. Aubin HJ et al., BMJ 2012, meta-analysis of 62 studies. Rounded pooled estimates.
Over 60 percent of the first-year gain arrives within three months, the same window in which most relapses happen.
Share of abstinent quitters by weight change at 12 months
Aubin HJ et al., BMJ 2012. Approximate proportions.
Nearly half of quitters gain more than 5 kg. One in six loses weight.
Why does quitting nicotine cause weight gain?
Quitting nicotine causes weight gain because nicotine both burns extra energy and suppresses appetite, and removing it reverses both at once. In a 1986 NEJM study, Hofstetter and colleagues measured 24-hour energy expenditure in smokers in a metabolic chamber and found that smoking 24 cigarettes a day raised it by about 10 percent, around 200 kcal. Nicotine also acts on appetite-regulating neurons in the hypothalamus, particularly the POMC neurons that signal fullness.
Behaviour adds to the physiology. A cigarette delivers a dopamine hit in seconds, occupies the hands and mouth, and marks the end of meals and the breaks in a working day. When the cigarette goes, food fills several of those roles, and the foods that fill them are rarely vegetables. Studies of new quitters consistently show a shift towards sweet and high-fat snacks in the first weeks. Taste and smell also recover after quitting, which makes food more rewarding just as the brain is looking for a substitute reward. Our article on taste changes covers how GLP-1 drugs affect food preference from the other direction.
Do GLP-1 drugs help people quit smoking?
GLP-1 drugs have shown a benefit for quitting in one small trial and no benefit in a larger one, so the honest answer is "possibly, but not proven." The first trial, published by Yammine and colleagues in Nicotine and Tobacco Research in 2021, randomised 84 adults with prediabetes or overweight to exenatide 2 mg once weekly or placebo, both alongside a nicotine patch, for six weeks. Seven-day abstinence at the end of treatment was 46 percent with exenatide and 27 percent with placebo. Exenatide also reduced cravings, withdrawal symptoms, and weight gain among those who quit.
The second trial, by Lengsfeld and colleagues in eClinicalMedicine in 2023, was larger and used a stronger comparator. It randomised 255 smokers in Switzerland to dulaglutide 1.5 mg weekly or placebo for 12 weeks, with everyone also receiving varenicline and counselling. Abstinence was about 63 percent in both groups, so dulaglutide added nothing to quit rates on top of varenicline. Weight told a different story: the dulaglutide group ended slightly lighter than they started, while the placebo group gained.
Observational data point in a favourable direction. A 2024 analysis in the Annals of Internal Medicine by Wang, Volkow, and colleagues used US health records from people with type 2 diabetes and tobacco use disorder. Those prescribed semaglutide had fewer medical encounters for tobacco use disorder and fewer prescriptions for cessation drugs than those starting other diabetes medicines. Records-based studies cannot rule out differences between the groups, so they support further trials rather than settle the question.
Exenatide cessation trial: 7-day abstinence at week 6
Yammine L et al., Nicotine and Tobacco Research 2021. 84 smokers with prediabetes or overweight; all received a nicotine patch. Rounded.
- Exenatide 2 mg + patch
- Placebo + patch
A 19-point difference in a small, short trial. The larger dulaglutide trial, against a varenicline background, found no difference in quit rates.
How might GLP-1 drugs affect nicotine craving in the brain?
GLP-1 drugs appear to blunt the dopamine response that makes nicotine rewarding, based mainly on animal research. In a 2013 study by Egecioglu and colleagues, the GLP-1 agonist exendin-4 blocked nicotine-induced dopamine release in the nucleus accumbens of mice and stopped the animals from learning a preference for the place where they received nicotine. A 2017 Nature Neuroscience study by Tuesta and colleagues found that GLP-1 receptors in the medial habenula, a small brain region that signals when nicotine intake is excessive, act as a brake on how much nicotine mice take.
The same reward-dampening effect has been studied for alcohol and other substances, which our article on GLP-1 and addiction recovery covers. Mouse data does not translate neatly to people, and human brain-imaging studies of GLP-1 drugs in smokers are still few. What the mechanism does explain is why the trials see an effect on cravings and weight more reliably than on quit rates: dampening the reward from a cigarette is not the same as removing the habit, the stress triggers, or the social cues.
Which cessation aids work best, and can they be combined with a GLP-1 drug?
Varenicline is the most effective single cessation medicine, and it has been combined with a GLP-1 drug in a randomised trial without new safety signals. The EAGLES trial (Anthenelli, Lancet 2016), which randomised 8,144 smokers, found continuous abstinence at weeks 9 to 12 of 33.5 percent with varenicline, 23.4 percent with a nicotine patch, 22.6 percent with bupropion, and 12.5 percent with placebo. Any of these roughly doubles or triples the odds of quitting compared with willpower alone, and they remain the first-line tools.
A GLP-1 drug is best thought of as an adjunct aimed at weight and craving, not a replacement for proven cessation medicine. The main practical overlap is nausea. Around a quarter of varenicline users report nausea, and nausea is also the most common early GLP-1 side effect, so starting both at full strength in the same week invites trouble. A low, stable GLP-1 dose reduces that overlap. Our guide to managing nausea on a microdose has practical steps.
EAGLES trial: continuous abstinence, weeks 9 to 12
Anthenelli RM et al., Lancet 2016. 8,144 smokers with and without psychiatric history. Whole-trial rates, rounded.
Varenicline nearly tripled the placebo quit rate. These are the drugs a GLP-1 protocol would sit alongside, not replace.
| Cessation aid | Overlap with GLP-1 effects | Practical note |
|---|---|---|
| Varenicline (Chantix, Champix) | Nausea in roughly a quarter of users; GLP-1 drugs also cause nausea, mostly early and dose-related | Take varenicline after food with a full glass of water; keep the GLP-1 dose low and steady during the first varenicline weeks |
| Nicotine replacement (patch, gum, lozenge) | Little direct overlap; nicotine gum and lozenges can upset the stomach if chewed fast | Used in the exenatide trial alongside the GLP-1 drug; the combination was tolerated |
| Bupropion (Zyban, Wellbutrin) | Can reduce appetite and cause dry mouth or insomnia; seizure risk rises with very low body weight or eating disorders | Worth telling the prescriber about rapid weight loss or very low food intake |
| Cytisine / cytisinicline | Mild nausea and sleep disturbance reported, generally less than varenicline | Availability varies by country; same stomach-first precautions apply |
Is post-quit weight gain worse for health than smoking?
Post-quit weight gain is far less harmful than continuing to smoke. In the Framingham Offspring cohort, Clair and colleagues (JAMA 2013) followed 3,251 adults for about 25 years. People who had quit within the previous four years had a hazard ratio for cardiovascular events of about 0.47 compared with current smokers, and most of them had gained weight. Adjusting for that weight gain barely changed the result.
A 2018 NEJM analysis by Hu and colleagues, drawing on three large US cohorts, reached the same conclusion for mortality: quitters had lower death rates than smokers whether they gained little weight or a lot. The same analysis found one real cost. Diabetes risk rose for several years after quitting, peaking around five to seven years later, and the rise tracked the amount of weight gained. That is the specific problem a weight-management plan during a quit attempt can address, and it is a stronger reason to plan than appearance.
Cardiovascular event risk relative to current smokers
Framingham Offspring cohort, Clair C et al., JAMA 2013. Hazard ratios, rounded; never-smoker value approximate.
Recent quitters, most of whom had gained weight, already had about half the risk of people who kept smoking.
Why can coffee feel stronger after quitting smoking?
Coffee often feels stronger after quitting because tobacco smoke speeds up the liver enzyme that clears caffeine, and that speed-up fades once smoking stops. Polycyclic aromatic hydrocarbons in smoke induce CYP1A2, and smokers clear caffeine roughly 1.5 to 2 times faster than non-smokers. Within days to a couple of weeks of quitting, CYP1A2 activity falls back, and the same four cups of coffee can produce blood caffeine levels about double what the person is used to.
The result is restlessness, a racing heart, irritability, and poor sleep, all of which look a lot like nicotine withdrawal and can push someone back towards a cigarette. Cutting coffee by about half in the first weeks after quitting is a simple fix. The same enzyme change can raise levels of clozapine, olanzapine, and theophylline, so anyone taking those should tell their prescriber before their quit date. Semaglutide and tirzepatide are broken down by other routes and are not affected. Our article on caffeine and GLP-1 timing has more on coffee habits during a protocol.
How could a low-dose GLP-1 protocol be timed around a quit date?
A low-dose GLP-1 protocol would usually start two to four weeks before the quit date, so that any early nausea has settled before withdrawal begins. No trial has tested microdose timing for smoking cessation. The exenatide trial started drug and patch together, and the dulaglutide trial started both drugs a week before the quit date. The reasoning for an earlier start is practical: withdrawal peaks in the first one to two weeks after quitting, and it is easier to tell the difference between GLP-1 nausea and withdrawal irritability if they do not arrive together.
The goal of the GLP-1 dose in this setting is modest. It is to blunt the extra 200 to 300 kcal a day that new quitters tend to eat and to take the edge off evening snacking, not to produce major weight loss during a period that is already demanding. A dose that keeps weight flat through the first three months, when most of the post-quit gain would otherwise occur, has done its job. The chart below shows the pacing idea, not a prescription.
Illustrative 16-week plan: low GLP-1 dose started before a week-4 quit date
Weekly semaglutide-equivalent dose in mg (left axis) and cigarettes per day (right axis). Illustration of pacing only; dosing is a prescriber decision.
- GLP-1 dose (mg/week)
- Cigarettes per day
The dose steps up only once, after the hardest withdrawal weeks have passed.
What is the takeaway for someone who wants to quit?
The takeaway is that quitting comes first and weight is a secondary problem worth planning for, not a reason to delay. Proven cessation medicine, counselling, and a quit date do the heavy lifting. A GLP-1 drug has the best evidence for the part that derails so many attempts, the steady post-quit weight gain, and weaker evidence for improving quit rates on its own. For the nurse from the opening, the change that mattered on her fourth attempt was not willpower. It was knowing that the 11 p.m. toast was nicotine withdrawal talking, and having a plan for it before week six arrived.
"Five kilos gained after quitting is a manageable problem. Five more years of smoking is not."
Frequently asked questions
How much weight do people gain after quitting smoking?
A 2012 BMJ meta-analysis of 62 studies by Aubin and colleagues found that people who quit without medication gained an average of about 4.7 kg (10 lb) at 12 months. Most of that gain came in the first three months. The spread was wide: about 16 percent of quitters lost weight, while about 13 percent gained more than 10 kg.
Why do people gain weight when they stop smoking?
Nicotine raises resting energy expenditure and suppresses appetite, so removing it tips energy balance in both directions at once. A classic 1986 study by Hofstetter found that smoking 24 cigarettes a day raised 24-hour energy expenditure by about 10 percent, roughly 200 kcal. Quitters also tend to eat more, especially sweet and high-fat foods, as food partly replaces the reward and hand-to-mouth habit of smoking.
Can GLP-1 medications help people quit smoking?
The evidence is mixed. In a 2021 trial of 84 smokers, exenatide 2 mg weekly plus a nicotine patch produced 46 percent abstinence at six weeks against 27 percent on patch plus placebo, and reduced post-quit weight gain. A larger 2023 trial of dulaglutide added to varenicline did not improve quit rates, although it did prevent weight gain. No GLP-1 drug is approved for smoking cessation.
Do GLP-1 drugs prevent weight gain after quitting smoking?
Both randomised trials so far found less weight gain after quitting in the GLP-1 groups. In the dulaglutide trial, participants taking the drug lost around a kilogram over 12 weeks while those on placebo gained a similar amount, and the exenatide trial reported about 2.5 kg less gain among quitters. Neither trial used low doses, so the effect of a microdose protocol on post-quit weight has not been tested.
Is the weight gain from quitting smoking worse for health than continuing to smoke?
No. In the Framingham Offspring cohort (Clair, JAMA 2013), people who had quit within the previous four years had about half the cardiovascular risk of current smokers even though most had gained weight. A 2018 NEJM analysis by Hu and colleagues found lower death rates in quitters regardless of how much weight they gained. Diabetes risk does rise temporarily in quitters who gain weight, which is one reason weight management during a quit attempt is worth planning.
Can I take varenicline and a GLP-1 medication at the same time?
There is no known pharmacokinetic interaction between varenicline and semaglutide or tirzepatide, and the 2023 dulaglutide trial gave both drugs together. The practical issue is nausea, which affects roughly a quarter of varenicline users and is also the most common GLP-1 side effect. Keeping the GLP-1 dose low and steady during the first weeks of varenicline, and taking varenicline after food, reduces the overlap. The combination should be agreed with a prescriber.
Does quitting smoking change how other medications work?
Yes. Tobacco smoke induces the liver enzyme CYP1A2, and that induction fades within days to weeks of quitting. Caffeine, clozapine, olanzapine, theophylline, and some other drugs cleared by CYP1A2 can reach much higher levels as a result; caffeine levels can roughly double. Semaglutide and tirzepatide are not cleared by CYP1A2, but coffee intake may need to fall to avoid jitteriness and poor sleep that can be mistaken for withdrawal.
When should a GLP-1 protocol start relative to a quit date?
No trial has tested the ideal timing for a low-dose protocol. The exenatide trial started drug and nicotine patch together, and the dulaglutide trial started both drugs a week before the quit date. A practical approach used by some prescribers is to begin the low GLP-1 dose two to four weeks before quitting, so early nausea has settled before withdrawal and any cessation medication begin. Timing is a decision for the person and their prescriber.
Clinical references
- Aubin HJ, Farley A, Lycett D, Lahmek P, Aveyard P. Weight gain in smokers after quitting cigarettes: meta-analysis. BMJ. 2012;345:e4439.
- Yammine L, Green CE, Kosten TR, et al. Exenatide adjunct to nicotine patch facilitates smoking cessation and may reduce post-cessation weight gain: a pilot randomized controlled trial. Nicotine and Tobacco Research. 2021;23(10):1682-1690.
- Lengsfeld S, Burkard T, Meienberg A, et al. Effect of dulaglutide in promoting abstinence during smoking cessation: a single-centre, randomized, double-blind, placebo-controlled, parallel group trial. eClinicalMedicine. 2023;57:101865.
- Wang W, Volkow ND, Berger NA, Davis PB, Kaelber DC, Xu R. Association of semaglutide with tobacco use disorder in patients with type 2 diabetes: target trial emulation using real-world data. Annals of Internal Medicine. 2024;177(8):1016-1027.
- Anthenelli RM, Benowitz NL, West R, et al. Neuropsychiatric safety and efficacy of varenicline, bupropion, and nicotine patch in smokers with and without psychiatric disorders (EAGLES). Lancet. 2016;387(10037):2507-2520.
- Clair C, Rigotti NA, Porneala B, et al. Association of smoking cessation and weight change with cardiovascular disease among adults with and without diabetes. JAMA. 2013;309(10):1014-1021.
- Hu Y, Zong G, Liu G, et al. Smoking cessation, weight change, type 2 diabetes, and mortality. New England Journal of Medicine. 2018;379(7):623-632.
- Hofstetter A, Schutz Y, Jequier E, Wahren J. Increased 24-hour energy expenditure in cigarette smokers. New England Journal of Medicine. 1986;314(2):79-82.
- Egecioglu E, Engel JA, Jerlhag E. The glucagon-like peptide 1 analogue exendin-4 attenuates the nicotine-induced locomotor stimulation, accumbal dopamine release, conditioned place preference as well as the expression of locomotor sensitization in mice. PLoS One. 2013;8(10):e77284.
- Tuesta LM, Chen Z, Duncan A, et al. GLP-1 acts on habenular avoidance circuits to control nicotine intake. Nature Neuroscience. 2017;20(5):708-716.
- Kroon LA. Drug interactions with smoking. American Journal of Health-System Pharmacy. 2007;64(18):1917-1921.
- Filozof C, Fernandez Pinilla MC, Fernandez-Cruz A. Smoking cessation and weight gain. Obesity Reviews. 2004;5(2):95-103.
Medical disclaimer. This article is for general educational and informational purposes only. It is not medical advice, not dosing instruction, and not a substitute for the prescriber, pharmacist, or stop-smoking service responsible for your care. No GLP-1 medication is approved for smoking cessation or for preventing weight gain after quitting, and the trials described used standard doses, not low-dose protocols. The 16-week plan is an illustration of pacing and is not a recommendation for any individual. GLP-1 microdosing is an off-label approach and should only be undertaken under a prescriber's supervision. Nothing here describes a treatment for nicotine dependence, obesity, or any other condition. Anyone taking clozapine, olanzapine, theophylline, or other medicines affected by smoking should speak to their prescriber before their quit date. Low mood, agitation, or thoughts of self-harm during a quit attempt require prompt medical attention.