Cymbalta (Duloxetine) is a drug that us utilized primarily to treat major depression. It was approved in 2004 by the FDA as an SNRI antidepressant, and would later receive approval for the treatment of neuropathy, fibromyalgia, and some cases of chronic pain. The fact that Cymbalta can be prescribed to treat a diverse number of conditions makes it among the most popular antidepressants of the past year.

In addition to treating a multitude of conditions, it is considered to have a relatively favorable side effect profile, specifically when it comes to weight. A major concern for most people when taking an antidepressant (and in some cases before they even try an antidepressant) is that they’re going to gain weight. While many antidepressants such as SSRIs are capable of causing weight gain, Cymbalta is different in that it is unlikely to cause weight gain.

Cymbalta: Weight Gain or Loss?

Most professionals consider Cymbalta to be a “weight neutral” antidepressant due to the fact that only 1% of people report weight gain while taking it, and 2% of people report weight loss. The majority of people don’t report any significant changes in weight and therefore regard the drug as not affecting weight. Being an SNRI, it affects the stimulatory neurotransmitter norepinephrine which is thought to help minimize any weight gain as a result of the serotonin increase.

How Cymbalta Causes Weight Gain (in some people)

In the very small percentage of people who gain weight while on Cymbalta, there are a number of factors that may lead to a weight increase. Some speculate that appetite changes, food cravings, and social eating may play a big role in causing weight gain. Below is a list of potential reasons this drug may cause you to pack on a few pounds.

  • Appetite increase: Those that end up gaining weight while on Cymbalta may attribute their gains to an appetite change. If they were severely depressed prior to taking it and had no appetite, the drug may have brought back a normal appetite, resulting in some weight gain. Others may have had no appetite problem prior to taking the drug, but noticed a significant increase after taking the drug.
  • Cravings: Some people notice that they crave certain foods while taking certain antidepressants. Although most people won’t crave any foods on an SNRI, some people will notice that they crave carbohydrates and other unhealthy sweets. If you notice food cravings that you didn’t have before you started using this medication, they may have resulted from the drug.
  • Fat storage: The drug may influence the way your body stores fat. While most people won’t experience any change in weight, those that pack on a few pounds may not be able to burn the same percentage of fat that they did prior to taking the drug. Although this is just a theory, it is one that should be considered.
  • Hormone changes: It’s possible that Cymbalta disrupts the body’s homeostatic hormone levels, especially when taken over the long term. While it’s impossible for most people to determine how hormones are affected over time, it’s a theory to consider. Over a long term, the drug may influence hormone production, affecting hormones that may burn fat and others that store it.
  • Interactions: Remember that its always possible that another drug may be interacting with Cymbalta to cause your weight gain. Many people end up thinking it’s the Cymbalta causing their weight gain, when the weight gain is really stemming from how another medication or drug they’re taking interacts with it. Always consider the fact that there could be an interaction.
  • Side effects: Not everyone will feel energized from this drug. In some cases, a person may feel sleepy, groggy, drowsy, or notice a drop in energy while taking it. If you start to feel fatigued as a side effect, understand that the fatigue may be causing weight gain. Those that feel tired from the drug are going to be less likely to get physical exercise and burn off the calories they’ve consumed.
  • Slow metabolism: This drug affects serotonin to approximately 10x the extent of norepinephrine. Therefore it is possible for some individuals to experience a slowed metabolism while taking it. Although the norepinephrine is thought to help keep metabolism high, not everyone has this effect.
  • Social eating: Those that experience a recovery in their depressive symptoms may be more likely to hang out with friends and partake in social events. Being social often means going out to eat with friends and “social eating.” Going out to eat on a more frequent basis is likely going to lead you to gain some weight.
  • Taste improvement: If food starts to taste better after you’ve been taking Cymbalta, it’s probably not a coincidence. When neurochemistry is altered in the brain, there’s no telling specifically how these alterations will affect someone. Those that notice an improvement in taste may be more likely to eat more food.

Note: Instead of singling out one particular factor that’s causing weight gain, realize that it could be a combination of the factors listed above.

How Cymbalta Causes Weight Loss

Among 2% of individuals that take Cymbalta, weight loss is a side effect. If you end up losing weight, there’s no telling exactly how much you’ll lose. Possible factors responsible for weight loss while on this drug include: decreased appetite, energy improvements, and a faster metabolism.

  • Appetite drop: Some people may notice that their appetite decreases when they start taking Cymbalta. A decrease in appetite may be attributed to side effects such as nausea or it may be a byproduct of the norepinephrine increase. Stimulation of the central nervous system tends to decrease a person’s appetite. Additionally if a person was overeating to cope with their depression, the medication may alleviate their depressive symptoms, thereby eliminating the coping mechanism of overeating. It is estimated that roughly 9% of people taking this medication experience a decrease in appetite.
  • Diarrhea: A side effect that people may experience is diarrhea. The laxative effect can lead to significant weight loss if the person is unable to use the nutrients in their food. Generally this is considered a short-term side effect. If the diarrhea is long lasting, it may be worth switching to a different medication.
  • Energy increase: Many people who lose weight notice that the drug provides them with increased energy throughout the day. Since it does have a norepinephrine component of action, it is believed to help increase a person’s energy levels. The increased energy may lead a person to engage in physical exercise or simply move around more than they were prior to taking this drug.
  • Nausea: Another effect that some people experience while taking Cymbalta is nausea. They may feel nauseous prior to eating meals and/or during consumption of food. Feeling nauseous is a quick way to decrease a person’s appetite. In some extreme cases, this may lead to vomiting, which can also contribute to weight loss.
  • Speeds up metabolism: The stimulatory effect of the norepinephrine in this drug is believed to speed up a person’s metabolism. A sped up metabolism can result in unexpected weight loss without increasing exercise or making dietary changes. If you have a slow baseline metabolism and notice weight loss while taking this drug, there’s a chance that it was sped up.
  • Vomiting: In rare cases, some people experience vomiting while their body adjusts to this medication. If vomiting lasts more than a few weeks, obviously seek immediate medical attention as this may be a sign that you can’t tolerate this drug. Vomiting will result in weight loss, sometimes to a significant extent.

Factors that influence weight changes on Cymbalta

Those that experience and/or notice weight changes while taking Cymbalta can chalk the gain or loss up to a few factors. These factors include: the drug’s dosage, how long they’ve been taking it, lifestyle changes or habit changes that were made while on the drug, as well as interactions with other medications.

1. Dosage

There are different dosing recommendations for those taking Cymbalta. If you are on the minimal effective dose for your depression, you will be more likely to remain weight neutral than at higher doses. At higher doses, the drug has greater influence over your natural homeostatic functions.

When the drug has become increasingly influential over natural processes, this results in weight loss and/or gain depending on the individual. Just know that the higher the dose, the greater the likelihood you’ll experience weight changes.

2. Individual factors

It is also important to analyze various individual factors that could be culpable for weight gain. Many people want to place 100% blame on the medication they’re taking for the changes they experience in weight. In reality, your genetics, hormones, dietary intake, exercise habits, sleep quality, and the amount of stress in your life also have a great influence over your body weight.

If you started eating unhealthy foods while taking this drug and gained weight, that factor alone could be to blame. On the opposite end of the spectrum, if you started eating healthier while on the drug, this could account for some weight loss.  If you want more perspective on how your genetics may be influencing your reaction to Cymbalta and other antidepressants, consider checking out the GeneSight test.

3. Time span

The length of time that you’ve been medicated plays a role in determining the amount of weight change that you’ll experience. Those that have been medicated with Cymbalta for an extended period of time tend to build up a tolerance to the drug’s effects. This often leads to an increase in dosing, which we already discussed is likely to lead to weight changes. Those that have been on the drug for a shorter term may not notice much (if any) changes in their weight.

4. Other medications/drugs

While it is often very difficult to determine that other drugs may interact with Cymbalta to increase or decrease weight, it is a very real possibility. For example, if you are taking a stimulant medication along with Cymbalta, there is an increasingly good chance that you’ll lose weight. On the other hand, if you are taking a drug like an antipsychotic that is sedating, you will be very likely to gain weight. Always consider the effects of other drugs if you are medicating with multiple substances.

How much weight will you gain or lose from Cymbalta?

The amount of weight change you experience will be based on many of the factors listed above. Most people who gain weight end up gaining less than 5 pounds (on average) throughout their treatment. Those that lose weight may lose between 5 and 15 lbs. There’s no way to know how you will react to the medication (in terms of weight change) until you’ve taken it for an extended period of time. An advanced study revealed that after 52 weeks of treatment, the average weight gained was only 2.5 pounds; this is relatively minimal.

Cymbalta: Cost-Benefit Analysis

If you have experienced significant weight changes while taking Cymbalta, and they are making you unhappy, you conduct an evaluation. This evaluation will involve weighing the benefits you’ve experienced while taking the medication and comparing them with the costs (or drawbacks) you’ve endured. If you’ve packed on a significant amount of weight, and the drug isn’t really helping your depression, you may want to switch drugs or go through with Cymbalta withdrawal. If on the other hand the medication has significantly helped your depression, but you’ve gained some weight, the minor weight change is probably worth the benefit you’ve received.

Did you experience weight changes while on Cymbalta?

If you have taken Cymbalta, feel free to share whether you experienced any weight changes while taking it. If you gained weight, feel free to share how much, the dosage you were taking, and any other specific factors that may have contributed. If you lost weight, feel free to do the same.

This may help others pinpoint some similarities among those who ended up gaining vs. losing weight on the drug. Also if you remained relatively weight-neutral while on this drug, feel free to comment. Understand that everyone has a different experience in regards to weight change on Cymbalta.

  • Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1764530/