Remeron (also known as mirtazapine) is an antidepressant drug that is not related to any of the other antidepressants, such as the Prozac or Zoloft. Treating depression can result in weight gain. Many people gain weight because they are actually getting better and their appetites are improving. But if the weight gain continues after several months, the drug may be the cause.

The older tricyclic antidepressant drugs (such as amitriptyline and doxepin) and the MAO inhibitors (such as Parnate) are often cited as the most likely antidepressant drugs to cause weight gain. Remeron is the next most likely to cause weight gain. Most of the drugs in the selective serotonin reuptake inhibitor (SSRI) category (such as Prozac, Celexa, Zoloft and Lexapro) are less likely to cause weight gain than the older drugs. An exception is the SSRI Paxil, which seems more likely than the others to cause weight gain. The least likely antidepressant drugs to cause weight gain appear to be bupropion and nefazodone. It is important to recognize that this is based on impressions, not on studies.

The cause of the weight gain is likely to be a combination of increased appetite and a reduction in metabolism. As with any weight gain, diet and exercise are the answer. Quick fixes don't work, despite what the sellers of herbal products and exercise machines say. Most experts in weight loss say a gradual approach to dietary change and exercise (a healthy lifestyle) is the right approach.