Most people that i know seem to have gained weight on certain antidepressants, even when they’ve been eating the same and hitting the gym and claim to not be able to get rid of this weight no matter what they do.
What causes this? How do antidepressants change your metabolism?
In: Biology
While I’m not an expert on any of this I believe it’s not weight that they are putting on but rather the body is swelling up. That’s why exercising isn’t working. But I could be completely wrong about this.
We don’t have a definitive answer, but there are a few different possibilities.
First line anti depressants nowadays are called SSRIs, and they affect your serotonin levels. Brain serotonin does have an impact on your appetite, and an increase or decrease can affect your appetite, sometimes more, sometimes less. Serotonin, in addition to being a “happy” chemical for your brain, is also used in your intestinal tract as a transmitter. So while the medication mostly works on your brain serotonin, they also might have an effect on your gut serotonin, and this adjustment can have an impact on your weight.
Also, people typically tend not to eat when they’re depressed (or anxious, which SSRIs also treat). People typically lose weight when dealing with their mental health. As a rebound effect, when they get better because of their medication, their appetite returns and they gain weight from starting to eat regularly again.
There’s also been discussions about how SSRIs can affect your gut biome. I believe some small studies have shown that they might decrease the levels of bacteria in your gut. The bacteria in your gut is increasingly being looked at as to how it relates to our overall health, so that might play a role as well.
Other anti depressants might have differing reasons for why they cause weight gain, but this is a brief overview of how it *can* happen. It’s also most likely that it’s some combination of these factors, plus others we might not be aware of (or that I’m forgetting to mention). It’s likely that there isn’t one singular answer, but a combination of multiple.
Several things:
– most commonly used antidepressants (SSRIs/SNRIs) don’t cause statistically significant weight gain. Many people report subjective weight gain, but the numbers aren’t supported by data. One notable exception is paroxetine, which does consistently show some weight gain.
– there are other antidepressants that are widely known to cause weight gain, namely mirtazapine. This is presumed to be due to its effects on the histamine receptor. The medication is often chosen to help elderly patients who need to gain weight, so it’s not always an undesirable side effect.
– finally, meds from other classes – specifically antipsychotics and mood stabilizers – that are used to treat depression are known to cause weight gain. For unipolar depression, these meds are not first-line choices and are not indicated to be used alone; primary med usually still will be SSRI/SNRI. Bipolar depression is essentially its own disease entity that doesn’t respond to usual antidepressants; the medications approved for its treatment basically all cause weight gain.
– for many people, disrupted appetite is a symptom of depression. When the depression gets better, appetite improves.
– there are several neurotransmitters implicated in weight gain – notably histamine and very specific serotonin receptors – but we can’t study this directly. Essentially all antidepressants hit multiple neurotransmitter receptors, and we can’t reliably or easily tease out which does which.
– aging also decreases metabolism, but people generally want to attribute something like that to an external factor (the medication) rather than themselves/their body. For women in particular, estrogen significantly influences body fat retention as well as where weight is carried on the body.
– we are learning more about hunger, satiety, and how this influences and is influenced by weight with the explosion of GLP1 antagonists; I suspect we’ll soon have more quantitative data about how different medications affect our weight.
Hope this was helpful!
Source: am psychiatrist.
Personally, I was told that I had developed insulin resistance as a result of my use of Effexor. Sugar doesn’t just turn into body fat on its own, it’s targeted by insulin which increases weight. My body was sending 3x as much insulin as necessary to deal with any given sugars, and a doctor told me that it was because of anti-depressants. When I halved my antidepressant I lost 40 lbs in 6 months.
Had a psychiatrist tell me that most studies of medications were done in psychiatric hospitals. If patients were depressed enough to be hospitalized, they hadn’t been eating for some time. Suddenly the drug makes them feel better, and food at psychiatric hospitals is all you can eat buffet style. So weight gain gets reported as a side effect.
Fwiw, it’s basically impossible to gain weight if they are truly eating and hitting the gym “the same” as before. There is only one way the human body gets heavier: through its mouth. The medication increases appetite so the patient is eating more than when they were depressed.
Depression makes people either less hungry or they just cannot be bothered to prepare food so they don’t.
Antidepressants fix the depression meaning people feel more able to face day to day activities such as preparing food.
So they eat more but don’t necessarily increase the moving they do and they get a bit heavier.
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