Does Buspar Cause Weight Gain?
Weight gain is listed only as an uncommon effect in the buspirone label.
By withClaro Editorial · 2026-11-02 · 4 min read
Clinical section reviewed by Dr. Jason Tan , Consultant Psychiatrist, on October 27, 2026.
Key takeaways The buspirone label lists weight gain and weight loss as infrequent, between 1 in 100 and 1 in 1,000 people, in observations without a comparison group. Its controlled trials lasted 3 to 4 weeks, too short to measure weight; a year-long study tracked side effects, not weight. Buspirone isn't an antidepressant, so antidepressant weight studies give only a sense of scale, not its own risk. Tell your prescriber about any steady change in appetite or weight. On this page
How Buspar compares on weight, by the labels Why could weight change on Buspar? What should you tell your prescriber about weight changes? Buspar (buspirone) has hardly been studied for weight. Its FDA label lists weight gain and weight loss, and also increased appetite and loss of appetite, as infrequent, meaning 1 in 100 to 1 in 1,000 people, so change can go either way. That comes from reports across all its early studies, where it cannot be said whether buspirone caused them. Its controlled trials lasted 3 to 4 weeks, too short for weight to change, so the absence of weight in them proves little. In one study, 264 people took it for a year without ill effects, but weight was not reported.
How Buspar compares on weight, by the labels
Of these four labels, only buspirone's shows no signal in either direction. FDA labels report weight and appetite in different ways, and each warns that its numbers can't be compared with other studies, so the table shows direction, not size.
Medicine What the label reports on weight or appetite Buspirone weight gain and loss, increased and decreased appetite, all infrequent, no comparison group Remeron (mirtazapine) weight gain 12% against 2% on placebo Effexor XR (venlafaxine) loss of appetite 10% against 3% on placebo Wellbutrin (bupropion) weight loss more common than on placebo
This compares labels, not head-to-head trials. For a sense of scale, the best data come from antidepressants, not buspirone. A 2024 US study of 183,118 people compared eight antidepressants with sertraline over six months. The differences were small, from about 0.22 kg less on bupropion to 0.41 kg more on escitalopram.
Why could weight change on Buspar? Medically reviewed by Dr. Jason Tan on October 27, 2026, this section only.
No one knows for sure: neither the label nor the studies used here measured weight on buspirone in people. Buspirone works differently from the medicines most linked to gain, acting mainly on a type of serotonin receptor, 5-HT1A, and its label lists both more and less appetite among infrequent effects. The changes people describe are more likely indirect: when anxiety eases, sleep and appetite can change too, and nausea early on can lower appetite. The general picture for medicines like these:
In the first weeks, some people lose a little weight because of nausea or a smaller appetite. Gain, when it happens, usually builds over months, though with a few medications it can start within weeks. It varies a lot between people on the same medication.
What you can do:
- Mention a steady rise at your next appointment, while the change is still small. - Raise weight loss that keeps going, or an appetite that has not come back after the first weeks. If weight changes in a way that bothers you, there is usually more than one way forward, and the choice is one to make with your prescriber. Stopping on your own can bring your anxiety back.
What should you tell your prescriber about weight changes?
Tell your prescriber what changed, when it started and how much it bothers you. It helps to tell them:
When you started buspirone, your dose and other medicines. When you first noticed a change in appetite or weight. Whether anxiety and sleep have changed too. Whether your clothes fit differently. Any history of an eating disorder. More on side effects in Buspar side effects .
Download on the App Store Appetite and energy can shift when anxiety changes. The withClaro app lets you log appetite, sleep, energy and mood each day, linked to your dose, and turns it into a report for your prescriber.
Frequently asked questions Does buspirone increase appetite? It can, though not often: the label lists increased appetite, and also loss of appetite, as infrequent effects, between 1 in 100 and 1 in 1,000 people. If your appetite changes, note since when and whether your anxiety changed at the same time.
Is buspirone better than an SSRI for weight? There is no head-to-head study. Buspirone isn't linked to weight gain in its label, while SSRIs differ from each other by small amounts. If weight matters to you, say so when you and your prescriber choose.
How long should you watch your weight on buspirone? Gain on medicines like these usually builds over months, so a single month says little. Keep an eye on it over the first few months rather than week to week.
Does buspirone with an SSRI cause weight gain? That depends mostly on the SSRI, and there is no study of the combination. In the 2024 US study, escitalopram was linked to about 0.41 kg more gain than sertraline over six months, small on average. Ask your prescriber how your combination compares.
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Sources BUSPIRONE HYDROCHLORIDE tablets prescribing information, US Food and Drug Administration via DailyMed REMERON (mirtazapine) prescribing information, US Food and Drug Administration via DailyMed EFFEXOR XR (venlafaxine) prescribing information, US Food and Drug Administration via DailyMed WELLBUTRIN XL (bupropion) prescribing information, US Food and Drug Administration via DailyMed Petimar J, et al. Medication-induced weight change across common antidepressant treatments. Annals of Internal Medicine, 2024 Claro articles are for self-monitoring and educational purposes only. They are not a medical device, therapist, or diagnostic tool, and do not replace care from your prescribing clinician. If you are in crisis, contact your care team, emergency services, the Samaritans (UK: 116 123), or the Crisis Text Line (US: text HOME to 741741).