How to Manage Weight Gain from Psychotropic Medications

When you start taking medication for depression, bipolar disorder, or schizophrenia, the goal is to feel better-less anxious, more stable, able to get through the day. But for many people, there’s a hidden cost: weight gain. It’s not just about clothes fitting tighter. This weight gain is biological, persistent, and linked to serious health risks like diabetes and heart disease. And it’s not rare. Around 30 to 50% of people on high-risk antipsychotics gain at least 7% of their body weight within the first year. That’s not a side effect you can ignore. It’s a medical issue that can shorten your life.

Why Do Psychotropic Medications Make You Gain Weight?

It’s not because you’re eating more or moving less-though those things can make it worse. The real reason is how these drugs interact with your brain chemistry. Most antipsychotics and some antidepressants block key receptors: histamine-1, serotonin-2C, and dopamine-2. When these receptors are turned off, your appetite goes up, your metabolism slows down, and your body starts storing fat more easily. Some people feel constant hunger, especially for carbs and sugary foods. Others just feel sluggish, making exercise harder.

The drugs with the highest risk? Clozapine and olanzapine. Studies show people on these can gain 4 kg in just 10 weeks-and up to 10 kg in a year. Even if you start at a healthy weight, you could end up overweight or obese. On the other end of the spectrum, lurasidone and aripiprazole cause minimal weight gain-often less than half a kilogram over a year. Paliperidone is also relatively neutral. This isn’t guesswork. These differences are backed by FDA data, clinical trials, and real-world patient outcomes.

Which Medications Are Most Likely to Cause Weight Gain?

Not all psychiatric drugs are created equal when it comes to weight. Here’s what the evidence shows:

It’s important to remember: even “low risk” drugs can cause weight gain over time. No antipsychotic is truly weight-neutral after years of use. But the difference in risk is big enough that it matters when choosing or switching medications.

What Happens When You Try to Lose Weight on These Medications?

If you’ve ever tried dieting or joining a weight-loss program while on psychiatric meds, you might have noticed something frustrating: it’s harder. A 2016 study of 885 people in a weight clinic found that those on psychotropic medications lost 1.6% less weight over 12 months than those not on these drugs. Only 63% of medicated patients lost at least 5% of their body weight-compared to 71% of those not taking them. For 10% weight loss? Just 32% of medicated people hit that mark, versus 41% of others.

Why? The drugs change your body’s biology. Your metabolism adapts to burn fewer calories. Your hunger signals stay turned on. Even when you eat less and move more, your body fights back harder than it would if you weren’t on medication. This isn’t about willpower. It’s biochemistry.

What Can You Actually Do About It?

There are three main strategies-and they work best together.

1. Switch medications-if your symptoms allow it. If you’re on olanzapine and stable, switching to lurasidone or aripiprazole might cut your weight gain in half. But don’t do this alone. Talk to your psychiatrist. Stopping or switching too fast can bring back symptoms. The goal is to trade one problem for a better one, not create a new crisis.
2. Add metformin. This diabetes drug is now a standard tool for managing weight gain from antipsychotics. Multiple studies show it helps people lose 2 to 4 kg compared to placebo. It works by improving insulin sensitivity and reducing appetite. Side effects? Mostly mild stomach upset at first. It’s safe, cheap, and widely used in mental health clinics in New Zealand, the U.S., and Europe.
3. Use structured lifestyle support. A dietitian who understands psychiatric meds can help you plan meals that fight cravings without triggering guilt. Exercise doesn’t need to be intense-walking 30 minutes a day, five times a week, makes a difference. Group programs that include mental health counselors, dietitians, and fitness coaches have the best results. One program in Wellington saw patients on antipsychotics lose 6% of their weight in six months with weekly check-ins and tailored meal plans.

Topiramate is another option. It’s an older epilepsy drug that also helps with weight loss-studies show 3 to 5 kg reduction in people with medication-induced weight gain. But it can cause brain fog or tingling, so it’s not for everyone. GLP-1 agonists like semaglutide (Ozempic) are being tested in psychiatric populations now, with early results showing 5 to 8% weight loss. But these are still new, expensive, and not yet approved for this use in New Zealand.

Monitoring Is Non-Negotiable

If you’re on any antipsychotic or mood stabilizer, you need regular check-ups-not just for your mood, but for your body. The American Psychiatric Association recommends checking your weight, waist size, blood sugar, and cholesterol at the start of treatment, then every three months. Many clinics in New Zealand now use digital tools to track this automatically. The Veterans Health Administration in the U.S. started mandatory metabolic screening in 2010 and saw a 15% improvement in catching problems early. You deserve that same level of care.

What About Stopping the Medication?

Some people stop their meds because of weight gain. A 2020 survey found that 15 to 20% of patients discontinue antipsychotics mainly because of this side effect. But stopping without a plan is dangerous. Relapse rates for schizophrenia and bipolar disorder jump dramatically without treatment. The risk of hospitalization, self-harm, or losing your job is far higher than the risk of gaining weight. The goal isn’t to avoid meds-it’s to use them smarter.

What’s Changing in 2026?

Science is moving fast. Researchers are now looking at genes that predict who’s more likely to gain weight on certain drugs. Early findings point to variations in the MC4R gene-this might one day help doctors pick the best drug for you before you even start. Digital tools are also helping. The FDA-cleared Moodivator app, launched in 2021, tracks food, mood, and activity. In a 2022 trial, people using it lost 3.2% more weight than those on standard care.

Final Thought: You’re Not Alone, and It’s Not Your Fault

Weight gain from psychiatric meds isn’t laziness. It’s not poor choices. It’s a biological response to powerful drugs that help you survive. The good news? You have options. You can work with your care team to switch meds, add metformin, or join a support program. You don’t have to accept weight gain as part of the deal. With the right plan, you can manage your mental health-and your body-at the same time.

What to Do Next

If you’re on a psychotropic medication and have noticed weight gain:

• Ask your psychiatrist: “What’s my risk for weight gain with this drug?”
• Request a baseline metabolic panel: weight, waist, blood sugar, cholesterol.
• Ask if metformin is an option.
• Seek out a dietitian who understands psychiatric medications-don’t use generic weight-loss plans.
• Track your progress monthly. Even a 2% weight loss can improve insulin sensitivity and blood pressure.

You don’t have to choose between mental health and physical health. With the right support, you can have both.