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Pristiq: Weight Gain or Weight Loss? Causes & Individual Factors.

Pristiq (Desvenlafaxine) is a drug that was approved for the treatment of major depression in 2007. It functions as an SNRI (serotonin-norepinephrine reuptake inhibitor) and increases extracellular levels of two neurotransmitters. In addition to treating depression, it is also being investigated as a non-hormonal approach to treating menopause.

This drug is considered very similar to the drug Effexor (Venlafaxine) – most consider it as being an “updated version.” Pristiq contains the active metabolite of Effexor and thus is relatively similar in its effects. The major difference between the two drugs is that Pristiq increases norepinephrine at nearly 3 times the amount of Effexor. While many find Pristiq effective as an antidepressant, it is capable of causing unwanted side effects, including weight changes.

Pristiq: Weight Gain or Loss?

Most people want to be reassured by their doctor that they will not gain weight when taking an antidepressant. Unfortunately it is impossible to make guarantees and predict which drug will cause you to gain weight and which will cause you to lose weight. In general, Pristiq is considered to be more weight neutral than the SSRIs – meaning that there’s less of a chance that you will gain weight.

Some individuals that take it will pack on the pounds, while others will end up losing weight. Others may end up staying at their normal baseline weight throughout treatment. It is believed that the norepinephrine reuptake inhibition helps offset the potential weight gain that would likely result from the serotonin reuptake inhibition.

How Pristiq Causes Weight Gain

There are several potential theories as to what may lead you to gain weight while taking Pristiq. If you’ve packed on some serious weight and you know it’s probably from the medication, below is a list of potential causes.

  • Appetite increase: Some people experience a noticeable appetite increase after they begin taking Pristiq. In other words, people feel hungry more frequently than they had prior to taking the drug. To cope with the hunger that they experience, they end up eating more. Others may gain some weight
  • Carb cravings: Any medication that affects the serotonin system has potential to create food cravings. Many people end up taking SSRIs and SNRIs and notice that they start to crave carbohydrates and other sugary foods. If you are craving pastas, pizzas, and candies, it may be a little more than a coincidence.
  • Drug interactions: It is important to keep in mind that Pristiq may not be the only culprit for your weight gain. If you are taking another medication, there’s always a possibility that Pristiq may be interacting with it to increase the amount of weight you gain. In some cases drugs work synergistically to slow the metabolism or make you pack on excess weight.
  • Fat storage: Most wouldn’t think that Pristiq would alter the way the body stores fat, but this is a theory to consider. If you were in good shape prior to taking Pristiq and you notice a build-up of fat in areas that were previously skinny, it’s likely a result of the medication. Some speculate that it may alter your body’s fat storage mechanisms over the long term.
  • Food taste: Certain people taking Pristiq end up experiencing an improvement in taste. This can lead to an increase in food consumption. If food didn’t taste very good when you were depressed and all-of-a-sudden it tastes amazing, you’re probably going to eat more.
  • Hormonal changes: It is possible that this drug alters hormone levels when taken over a long term. Some believe that changes in the levels of certain hormones may contribute to the amount of weight a person gains. For example, if a person’s level of cortisol increases throughout treatment, this could be a direct cause of gained weight.
  • Side effects: While Pristiq is considered an activating antidepressant, it doesn’t have this effect in every person. Some people may become groggy, tired, or fatigued while taking it. If you react to the drug by feeling sluggish or tired, you may be less likely to get proper physical activity or exercise, which could lead to weight gain.
  • Slow metabolism: Most people believe that Pristiq speeds up the metabolism, but not every person has this experience. If you believe that your metabolism slowed over the course of your treatment with Pristiq, you could be right.
  • Social eating: When people are depressed, they often isolate themselves from social events. When people feel happier, they are more likely to do things with friends and partake in social outings. Those that take Pristiq may start to feel happier and do things with friends, including social eating. Increasing the amount of times you go out to eat with friends is often a quick way to gain weight.

Note: In some cases weight gain is due to a combination of factors listed above. For others, there may be one primary factor that leads them to gain weight. Keep in mind that the way a person reacts to Pristiq is highly subject to individual variation.

How Pristiq Causes Weight Loss

Most people that lose weight while taking Pristiq do so within the first 6 months of treatment. It is common to experience weight changes during the first phase of treatment because the drug hasn’t had enough time to make long-term physiological alterations. Below is a list of reasons why people lose weight on Pristiq.

  • Appetite decrease: It is possible to take an antidepressant and experience a decrease in appetite. Those that aren’t as hungry as they were prior to taking the drug are more likely to eat less and end up losing some weight. While appetite decrease generally isn’t long lasting, it can cause some initial weight loss.
  • Diarrhea: A side effect of this drug is that of diarrhea. If you experience this side effect, it is likely a direct cause of weight loss. Anything that acts as a laxative is going to result in short-term weight loss. However, as your body stabilizes and adapts to the drug, you should gain the weight back that you lost via diarrhea.
  • Energy increase: Among some people, Pristiq tends to give them a significant increase in energy. If the person was depressed and sluggish prior to taking the drug, but now they are stimulated, they may be more likely to exercise and stay active. The increase in physical activity may lead to weight loss.
  • Metabolism increase: The fact that Pristiq increases extracellular norepinephrine results in stimulatory effects. The stimulation will speed up metabolism and could result in some degree of weight loss. In some individuals, the metabolic slowing from the serotonin increase is overridden by norepinephrine.
  • Nausea: A very common side effect associated with this medication is nausea. If you feel nauseous more than usual, you may be less likely to eat. Nobody wants to eat if they are feeling nauseous. Therefore this may be a direct cause of an appetite decrease and ultimately weight loss.
  • Vomiting: If you experience vomiting as a side effect of this drug, you are going to lose weight. Understand that this side effect generally subsides after a couple weeks and can be the cause of initial weight loss on this drug. Those that vomit over a longer span should seek immediate medical attention.

Why Pristiq is generally regarded as “weight neutral”

In clinical trials, Pristiq wasn’t found to produce any significant weight gain among those that took it. Therefore, the company that made the drug was able to promote it as a “weight neutral” antidepressant. This allows psychiatrists to tell patients that they won’t gain weight on this particular drug because it isn’t associated with any gain in weight. They can show the studies and results of them and suggest that if you gain weight on this drug, it’s your fault – not the drug.

Unfortunately this is a relatively skewed way of looking at things. In the clinical trials, some people likely gained weight, others likely lost a bit of weight, etc. Additionally clinical trials do not examine patients that have taken the drug for years – they simply analyze responses over a period of months. This may not fully reveal the potential to gain weight over a long-term treatment with Pristiq.

It’s important to keep in mind that anyone could still gain weight while taking this drug – especially over the long term. Everyone will have an individualized reaction and vary in the side effects that they experience. Although most evidence does suggest that the drug is weight neutral, it should be noted that some individuals will still likely gain weight from taking Pristiq.

Factors that influence weight changes on Pristiq

There are some other factors that you should keep in mind if you experience weight gain or loss while taking Pristiq. The factors that influence weight changes include: dosage of the drug, your lifestyle and habits, how long you’ve been taking the drug, and whether you are also taking other medications.

1. Dosage

At the moment, Pristiq is only recommended to be taken at the 50 mg dose. Those taking any dose higher than 50 mg are not getting any additional therapeutic benefit. Therefore, 50 mg is considered the minimal effective dose and only available dose of the drug. Despite the recommendation not to exceed 50 mg, some people still end up on higher doses.

The higher the dose, the greater potential a person has to gain weight from the drug. At higher doses, the drug is capable of making more changes to a person’s homeostatic physiology. The more control you give the drug over your functioning, the greater the likelihood that you’ll gain weight. Pristiq is offered at both 50 mg and 100 mg doses, but even 50 mg may feel too high for some individuals (especially those of smaller stature or size).  The greater the dose, the greater potential for weight fluctuation in response to the drug.

2. Individual factors

It is also important to consider individual factors that may be influencing weight changes. This includes things like your dietary intake, amount of exercise you get, your baseline bodyweight, sleep patterns, and stress levels. Your genetics also have significant influence over how you respond to the drug.

For this reason it is recommended to consider the “GeneSight” test that evaluates your genetics to predict how you will react to this drug. Always keep in mind that your lifestyle choices always have some potential influence over your weight, regardless of whether you are taking an antidepressant.

3. Time span

How long were you taking Pristiq? Those that take it over a shorter term are more likely to experience some sort of weight loss or remain weight neutral. It is believed that over the long term, weight gain is a more likely experience. This is because it often takes a long period of time (i.e. 6 to 12 months) for the drug to have made substantial changes to your physiological functioning and neurochemistry. The longer you’ve taken the drug, the more likely it is that you’re going to gain some weight (even if it’s a small amount).

4. Other medications/drugs

If you are taking any other medications (or drugs) in addition to Pristiq, it is important to consider that they also may be contributing to the amount of weight you gain. In some cases Pristiq can interact with other drugs and result in more weight gain than if you were only on a single medication.

Before you blame Pristiq for any weight gain, be sure to consider the fact that other drugs may also be contributing. Certain antidepressant augmentation strategies such as antipsychotics are very likely to cause weight gain. If you plan on discontinuing one medication to help minimize weight gain, be sure to talk to your doctor about it.

How much weight will you gain/lose from Pristiq?

There’s no research that documents the amount of weight gained or lost on Pristiq. Since a significant amount of weight wasn’t gained during clinical trials, researchers concluded that Pristiq is a “weight neutral” antidepressant and will not cause weight gain. The problem with this conclusion is that not everyone will find it to be weight neutral.

Some people will end up gaining a considerable amount of weight during the first 12 months (i.e. year) of treatment, while others may end up losing some weight. This demonstrates that Pristiq affects everyone differently. Certain people may lose 5 to 10 lbs. the first year of treatment, while others may gain 5 to 10 lbs. – there’s no telling how you’re going to react until you take it.

Pristiq: Cost-Benefit Analysis

If you are taking Pristiq, it is important to conduct a cost-benefit analysis of your experience. If the drug is working very well, a little bit of weight change may not be a big deal. For example, if you gain 5 to 10 lbs. your first year of treatment you may not care if your depression has markedly improved.

However, if you have packed on more than 10 lbs. (or lost a lot of weight), your depression hasn’t really improved, and you are experiencing other side effects, you may want to think about switching medications and/or Pristiq withdrawal. Always evaluate the benefits (improvements) resulting from your treatment and make sure they outweigh any costs (side effects).

Did you gain weight or lose weight on Pristiq?

If you have taken Pristiq, feel free to share any weight changes you experienced. If you gained weight while taking this drug, let us know how much weight you gained, whether you were taking the standard dosage, and how long you had been taking it. If you ended up losing a chunk of weight while on Pristiq, be sure to discuss how much you lost, and any factors that may have contributed to the weight loss. Others that have experienced no change in weight can also comment on their experience.

Feel free to mention any other factors that may have contributed to your weight gain and/or loss while on the drug. Did it boost your overall energy level? Did it make you feel more tired than usual or hungrier than normal? Although weight changes are common while taking the drug, most people eventually return to their baseline weight after they’ve discontinued Pristiq.

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{ 22 comments… add one }
  • Michelle May 7, 2015, 3:56 am

    I have gained 20 lbs in a year despite increasing my exercise and trying to eat healthier. I was on zoloft for a long time and got switched to pristiq. While on the zoloft I didn’t have any weight gain. Doc has tested my hormones and checked for hypothyroidism but everything comes back fine. I’m left to think it’s got to be the pristiq. I know everyone is different in the way they metabolize medicine but it appears that those who gain weight on pristiq are in the minority. Seeing my doc in a few days to switch back to zoloft. I’m hoping I won’t have any trouble weaning off the pristiq!

    • Katie October 7, 2015, 1:50 am

      I had the SAME experience! I gained quite a bit more than that though- I went from 125 lbs to 185 in a matter of 3 years. Finally my new doctor weaned me off of Pristiq and switched me to Zoloft. I feel so much better now. My appetite seems normal and my energy has finally returned. Please be warned- weaning off of Pristiq isn’t easy. Good luck to you, I wish you the best and I hope it all works out.

  • Jessica June 2, 2015, 1:28 am

    I have been taking 100mg of Pristiq for 2 years and have gained 20lbs. :(

  • Anne Harrington July 22, 2015, 12:50 am

    I have gained 10 to 15 lbs over a short period of time on 50 to 100 mgs/day after switching from Effexor XR 300mg/day and feel groggy! Terrible drug! Going back to going back to Effexor immediately!!!!

  • mandi September 10, 2015, 9:22 pm

    I have gained weight; 15-20 lbs in a 6 month period on this drug :(

  • Kacie November 12, 2015, 7:36 am

    I have been on pristiq for 6 months and gained 5kgs despite being very active at the gym and eating very healthy. I weigh 67kgs now. Every antidepressant I have tried has made me put on weight and when I have stopped I normally lose it. But then I go crazy and always end up having to be medicated. I was put on pristiq over other medications because of it being less likely to cause weight gain but it still does.

    The reason I need to take medication stems from a long string of eating disorders and serious anxiety towards weight related issues, but the medication is counterproductive in that it causes weight gain. It does feel like it allows me to be happier and more social and less anxious in other things though. The other side effects such as loss of coordination, sweating, brain zaps and loss of sex drive just don’t feel worth it.

    But living in my brain when I’m not medicated is no way to live either. Wishing there was something that could make me happy and not come with a world of side effects.

  • Belinda Lee January 16, 2016, 5:14 pm

    I have only been on Pristiq for approx 3 months but have lost 7.5kgs. I am also more motivated to eat healthier, although my energy levels are not higher and I seem more tired, hence not exercising ATM. Hoping that will change.

    • Ompy May 19, 2016, 4:19 am

      I have been taking Pristiq for about a year and have put on just over 10 kg. although I walk almost every day (and I mean very long walks), do sit ups, etc., and even tried cutting out carbs but to no avail. I am really feeling very unfit (even though I exercise), I am very tired, etc. and unhappy because clothes don’t fit and I don’t want to buy larger sizes. If anyone can help me with this I would be very grateful. My doctor just says “ELF” what’s that I ask; Eat Less Food. Many thanks.

  • Loz January 22, 2016, 10:49 am

    I’m 24 and been on Pristiq for about 2-3 years. I have gained about 10kgs since then but considering my age; not sure if I can fully blame Pristiq. Needless to say, I used to be too skinny and now I’m relatively normal… Wouldn’t want to gain any more though 😕.

  • Jodie R January 23, 2016, 6:48 am

    I’ve been on high dose (200mg) for severe depression for the past 2 years. My weight initially went down and then up and up and up and up. To my disappointment I’m topping the scales 13kg heavier which is 6kg heavier than I was at 40 weeks pregnant 😣!!! It certainly crushes self-esteem which contributes even more to depression. I will say this though… having been on so many other ADs with varying side effects over the past 20 years, this is the drug for me. I’d rather be fat and not depressed than slim and not functioning ☺.

  • Jane February 3, 2016, 2:16 am

    I have suffered from depression for thirty years, mainly because of chronic back pain. Started Pristiq 18 months and quickly rose to 200mg per day. I am in my seventies and have packed on 25kg which is bad for my back and also my self esteem. Have not had weight gain with previous medication. Am now weaning myself off and not finding it easy. Probably going back to Zoloft.

  • Lacey N February 7, 2016, 4:56 pm

    I’ve only been on Pristiq (50mg) for a couple of weeks for anxiety and mood issues. Since then I’ve lost almost 10 pounds due to loss of appetite and the inability to keep food down…it may seem like a bonus but honestly I just want to be able to eat normally again – I cant even enjoy myself or go out with people and eat a full meal. Hopefully it subsides as my body gets used to the medication.

  • Emma February 19, 2016, 2:16 pm

    I’m 32 and have been on it for 14 months. Have put on 16 KGS. Am a happy functioning female but the weight gain has been bittersweet. It’s one of the only things that gets me down… A lot more than I’d like as I have improved greatly with this medication. Dr denies it’s caused by pristiq but I’m very active and have had no changes to appetite.

    • Marlee February 20, 2016, 7:45 am

      Emma, after my experience I can tell you I am 99.9% sure that it is due to the Pristiq. There are other medications that work equally as well and do not have weight gain as a side effect. I encourage you to have a “serious talk” with your doctor. I would explain to him that “the weight gain is making you more depressed” and you want to try other medications that may not have weight gain as a side effect.

      I was put on Brintellix 3 weeks ago and I lost the weight that Pristiq had added. So far there are no side effects that I can tell. The only issue is I do not believe that Brintellix in generic but there are coupons online. Regardless of what other medications you try, your doctor needs to “LISTEN TO YOU”.

      If he/she doesn’t listen, please find a doctor who does listen. You know your body/mind better than anyone and ultimately you have to be your own advocate. I hope this helps and good luck!

  • Marlee February 20, 2016, 7:35 am

    I was on Pristiq for several years. I gained 25 pounds and prior to taking Pristiq I was always thin and very “in shape” as I worked out to build muscle tone. I tried everything to get the weight off: diet, exercise, running, and nothing worked. It seemed the harder I worked the more the weight stayed on. I asked my doctor if there was any other options because I felt like Pristiq was not beneficial anymore and I was experiencing extreme low energy.

    My doctor switched me to Brintellix and it has been wonderful. My weight is back to normal after three weeks. All I did was eat healthy and ride the bike for 30 minutes 5 days a week. I feel so much better about myself now that I can fit back into all my clothes. My advice is that if you are battling depression the last thing you need is to gain weight because that will just make you more depressed.

    I encourage you to talk to your doctor about other options. If your doctor “dismisses your weigh gain concern” simply tell your doctor that this weight gain had made my depression worse. If that doesn’t work, find a doctor that will listen to you because you are your best advocate.

  • R March 16, 2016, 2:12 am

    I’ve been on 100mg of Pristiq for just over two years. I have gained 40lbs and with healthy eating and exercise, I can’t lose it. Fortunately, I’ve seemed to stop gaining, but 40lbs is a lot!

  • Christine March 29, 2016, 2:47 am

    I used to be in great shape, I was a competition swimmer. I got on Pristiq and within the time of 7 months I gained between 50-60 lbs and I can’t get rid of it. :(

  • Charlie April 25, 2016, 6:50 am

    I have been on Pristiq for a few years because of horrible depression along with suicidal thoughts. I tried many drugs but one doctor put me on Pristiq and it to me was a lifesaver as far as depression goes, but the side effects are a pain. The weight gain has been around 40 pounds or so and can’t seem to lose any.

    Regardless of the nightmare some go through trying to get off of this med I am trying to at least cut back. They say don’t cut the pill in half but I am trying it and right now it has been working, only 5 days into it but not one side effect at all, not one and I am amazed because of all the negative feedback from others who have tried.

    I can only hope this will continue without side effects but I already feel much better, not as fatigued and even a bit happier in my mood, no depression at all has returned. I will continue on half a pill for a month and then a quarter pill and after a month nothing. I can only hope this works, they say pristiq is an almost impossible drug to quit.

    Like all of you, I sure would like to get rid of this extra poundage I’ve been packing around and to be able to tie my shoes once again.

  • Catherine June 3, 2016, 2:31 am

    I’ve been on Pristiq for 18 months & gained 12 pounds despite daily exercise and healthy eating. I was very anxious & very depressed when I started and not eating or sleeping well. After 4 months I felt 100% better mentally. I think I eat more because I don’t feel awful, but I’m still surprised by the weight gain and the weight is around my waist. Could also be peri-menopause contribution. Worth the weight gain to feel better, but going to see if I can lose it by cutting carbs. Glad to find that I’m not the only one.

  • Mishele July 9, 2016, 11:32 pm

    I’ve been on a combination of Topamax and pristiq for 5 days and I’ve already lost 10lbs.

  • Catherine McAdams August 30, 2016, 6:12 pm

    I was on Effexor ER 37.5mg capsules, (3), total 112.5mg. every morning for at least eight years. I was informed by my insurance company that my plan would no longer cover brand specific, I had tried the generic, and it was not as good. They even would not honor my doctors request for brand specific. They wanted $2,000 dollars a month for the Effexor.

    My psychiatrist suggested I go on Pristiq 50mg. I did in April. I have gained fifteen pounds! I do not like this drug. I am no longer depressed and my anxiety is under control, as well. My psychiatrist is following me for maintenance only. I have a great support system and am a 60 year old retired RN and mother of five grown children and have three grandchildren. I am blessed beyond measure.

    I want to come off the Pristiq. I am also on Clonazepam for anxiety. I take 0.5mg in the AM and PM. Please, I know I might have to go through withdrawal, but I believe it is worth it. I was told by my psychiatrist that I would have to be on some form of antidepressant for the rest of my life. I don’t know what to believe at this point. But I believe I can make it without these meds. What is the truth?

  • Rafael September 4, 2016, 4:42 pm

    In just one week I have gained about ten pounds. The problem is that the hunger doesn’t go away even after eating a heavy meal. I take other medications but Pristiq is definitely the culprit. I have switched my GAD to fat anxiety!

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