Medications That Can Cause Weight Gain

Some medications can cause weight gain or prevent weight loss, but knowing why and how can help you weigh the benefits of taking them. Cathleen McKnight, DNP, MS, NP-C, NCMP, discusses these medications and what you can do—and what you shouldn't do.

Person grabbing medication out of daily medication reminder container

Are Your Medications Affecting Your Weight?

Medications are designed to treat medical conditions, improve quality of life, and prevent complications. Alongside the many benefits that medications afford us come side effects as well. When it comes to weight gain or the inability to lose weight, it is a standard practice in obesity medicine to take a close inventory of medications a patient is taking and identify obesogenic medications.

Obesogenic medications are those that can cause weight gain and obesity or prevent weight loss when used long-term. Many people who take obesogenic medications will never gain weight, maintain weight, and do not have trouble losing weight. If you are on an obesogenic medication and your weight is stable, do not worry about it.

<p class="pro-tip"> If you are taking these medications and believe your weight is negatively impacted, consult a healthcare professional before stopping the medication. Abruptly stopping a medicine can cause a slew of problems. If your healthcare provider deems that the drug may be an issue, there may be options to thwart the impact on weight without discontinuing the medication.</p>

Obesogenic Medications

The mechanism in which an obesogenic medication may cause issues around weight vary. The severity of weight impact, if impacted at all, also differs by drug and individual response. Obesogenic medication classes tend to promote weight gain more than others, like antipsychotic and anti-diabetic medications <sup>1,2</sup> 

One study found that patients on any single obesogenic medication, irrespective of drug class, were 37 percent less likely to reach a minimum of 5 percent weight loss by the end of an eight-week weight loss program. The same study observed a 73 percent deficit in achieving 5 percent weight loss for individuals taking three or more obesogenic medications <sup>2</sup>. 

List of Medications Known to Cause Weight Gain

Categorically, commonly prescribed medication classes that may prevent weight loss success or promote weight gain include<sup>1</sup>:

  • Antidepressants
  • Antipsychotics
  • Anticonvulsants
  • Anti-diabetic meds
  • Antihypertensives (specifically, beta-blockers primarily)
  • Antihistamines
  • Hormones

Antidepressants

In the United States, an estimated 21 million adults have been affected by a major depressive episode <sup>3</sup>. With more than 1 in 10 Americans taking an antidepressant paired with the rising rate of obesity, the potential weight gain associated with the use of depression medications should be considered when a prescription is received, especially if you already experience weight challenges <sup>4</sup>.

Weight gain from antidepressants can result from an alteration in brain chemistry presenting as a medication side effect or may occur in response to treatment of symptomology. For example, individuals with depression may eat very little, overeat as a coping mechanism, or remain weight neutral without appetite and weight symptoms. However, when treated for depression, these same individuals may regain appetite, subdue episodes of overeating, or be unaffected in eating patterns and weight.

Nearly all antidepressants have shown weight gain to be a possible side effect, but that does not mean every person who takes the drug will experience a difference on the scale. The following antidepressants are more likely to pose a risk on weight:

  • Paroxetine (Paxil) and Sertraline (Zoloft), a serotonin reuptake inhibitor (SSRI),
  • Amitriptyline, imipramine (Trofranil), and doxepin (tricyclic antidepressants),
  • Mirtazapine (Remeron), an atypical antidepressant, and
  • Phenelzine (Nardil), an infrequently used class of antidepressants called monoamine oxidase inhibitors (MAOIs) that are typically reserved for complicated, treatment-resistant depression due to their testy nutritional and medication interactions and side effect profile (2,5,6).

The good news is that an alternate option is available for individuals who are overweight, obese, or experience weight gain when taking other antidepressants. Bupropion (Wellbutrin) is an atypical antidepressant that is known to stimulate weight loss through alteration in brain chemistry in the hypothalamus that regulate energy <sup>5,7</sup>.

Some research shows that fluoxetine (Prozac) is weight neutral and may demonstrate modest weight loss in obese patients who have a body mass index of 30 or greater. Even though other literature challenges this notion, it may be a prudent discussion to have with a healthcare provider if you are taking or considering starting medication for depression <sup>7,8</sup>.

<p class="pro-tip">Even if you experience weight gain with one medication, it does not mean that the same outcome will occur with all antidepressants.</p>

Antipsychotics

Antipsychotics are a well-known offender for their negative impact on weight, glucose levels, and triglyceride levels.

As a result of the metabolic influences, antipsychotic use is associated with the development of metabolic syndrome. Metabolic syndrome is a group of conditions that occur together and increase your risk of heart disease, stroke, diabetes, and other poor health outcomes. It is diagnosed when an individual carries three or more risk factors, which include:

  • High blood sugar,
  • Low HDL levels (the good, protective cholesterol),
  • High levels of triglycerides (a byproduct of fatty food we eat),
  • Large waist circumference, and
  • High blood pressure (9).

Over a 52-week period, one study demonstrated that 13.4 percent of the total patients taking antipsychotics were diagnosed with metabolic syndrome that emerged during treatment irrespective of gender. Treatment-emergent metabolic syndrome was detected at a short 3 to 4 months of use on average <sup>10</sup>. 

Anticonvulsants

Anticonvulsants are medications that are used to treat epileptic seizures. Anticonvulsants carry a well-known side effect associated with elevations in weight. Common anticonvulsants include valproic acid, carbamazepine, vigabatrin, and gabapentin <sup>11</sup>.

While the mechanism in which the medication triggers the accumulation of fat tissue and weight is not well understood, the center of the brain that controls appetite, also called the hypothalamus, can react to the medications with hunger stimulation. In addition, anticonvulsants decrease energy expenditure, reducing the caloric spend when the body is at rest <sup>12</sup>. 

Antidiabetic medications

Select medications used to treat type 2 diabetes have a well-established association with weight gain. Insulin, sulfonylureas, and thiazolidinediones (TZDs) are the antidiabetic therapeutic headliners for this issue <sup>13</sup>.

Insulin is a “growing and building” anabolic hormone that promotes fat cell formation and decreases daily energy expenditure. Since sulfonylureas increase the secretion of insulin, it yields similar results.

TZDs are sneaky as they often have no effect or can even decrease the nasty visceral fat that surrounds the major internal organs within the abdominal, while increasing subcutaneous fat that reside just below the skin and above the muscle <sup>14</sup>. While subcutaneous fat is generally harmless, it can accompany an undertoned, less desirable appearance.

Luckily, the first-line drug for treating type 2 diabetes, Metformin, shows substantial weight reduction benefits <sup>15</sup>. While Metformin sometimes is frowned upon related to its gastrointestinal side effects, most folks adjust quite nicely to this medication overtime with slow increases in dosing overtime.

Targeting diabetes prevention early through a healthy lifestyle and earlier initiation of Metformin can postpone disease progression into type 2 diabetes in adults with prediabetes by about 30 percent and assist with weight loss <sup>16</sup>.

The American Diabetes Association (ADA) recommends Metformin therapy in persons with prediabetes alone. The ADA strongly suggests that Metformin therapy be considered and prescribed for prediabetic individuals with a body mass index of 35 or greater, age less than 60, and women who experienced blood sugar issues in previous pregnancies (a condition called gestational diabetes) <sup>17</sup>.

Beta-blockers

B-adrenergic receptor blockers, also known as beta-blockers are commonly used for the treatment for elevated blood pressure and for years have raised eyebrows over their unfavorable metabolic impression. Traditional Beta-blockers have been shown to inhibit local vasculature and muscle activity, decreases fat burning, reduces exercise tolerance, increase fatigue, and decrease calorie expenditure at rest, which can ultimately effect a person’s lipid profile, insulin sensitivity, and weight <sup>2,18</sup>.

Experts attribute weight gain associated with traditional beta-blockers to decreasing energy expenditure <sup>19</sup>. The net gain in weight with the use of Beta-blockers can vary with an average modest weight gain of 2 to 3 pounds and an upward average threshold around 7 to 8 pounds. When beta-blocker associated weight gain occurs, it is most likely to be observed in the first few months of use without further insult thereafter <sup>18</sup>.

Not all beta-blockers are associated with weight gain. The slightly newer, third-generation beta blockers demonstrate weight neutral and possibly positive effects <sup>19</sup>. 

Antihistamines

Diphenhydramine (Benadryl), loratadine (Claritin), cetirizine (Zytrec), and fexofenadine (Allegra) are commonly used drugs for sniffles, sinus congestion, and allergies. When used on an as needed basis, it is unlikely that antihistamines will cause weight gain. However, when chronically used there appears to be a correlation with weight gain.

Since histamine is known to suppress appetite, it is logical that an antihistamine side effect includes stimulation of hunger and subsequent increased weight <sup>20</sup>.

Hormones

Hormones are chemical messengers in the body that regulate body functioning, like growth, metabolism, emotions, sexual function, and sleep. When steroid hormone medications are used for the treatment of inflammation and autoimmune diseases and prevent pregnancy, it alters the hormones and the corresponding message delivery to the brain.

Steroid hormones may negatively impact weight through water retention, increased appetite, shifts in metabolism, or the way the body processes and stores energy.

When it comes to steroid hormones, like prednisone and methylprednisolone (also called corticosteroids), are often used to treat inflammation and autoimmune disorders. When therapy is discontinued, the weight usually falls off. Prolonged use is associated with weight gain and fat redistribution to the face, back of the neck, and abdomen <sup>21</sup>.

Hormonal contraception used to prevent pregnancy has been shown to increase weight. With the evolution of dosing, this side effect is less impressionable now than in years past. When comparing combination estrogen-progesterone contraception with progestin-only contraception, the progestin-only contraception (for example, the “mini-pill” and “depo shot”) affects weight more <sup>22</sup>.

Steps You Can Take

Just because a medication can cause weight gain does not mean it will. Weight gain is just one possible side effect that may or may not occur. And, even if a medication is causing weight gain as a side-effect, the benefit of taking it may still outweigh the weight gain. 

If you are taking an obesogenic medication and think it may be affecting your weight, consider dietary and exercise changes to accommodate the change in energy expenditure.


<p class="pro-tip">PSA: Don’t stop or change the way you take a medication without first consulting your medical provider.</p>

1 - Understand the Pros and Cons

It is essential to weigh the pros and cons of the medication. If an obesogenic medication has a profound effect on prognosis or quality of life without alternatives or failed alternatives, it may be reasonable not seek a change in the medication.

Weight gain alone affects the hormones in the body. In addition, many of the obesogenic medications discussed above have been shown to alter fat cell break down and negatively impact cholesterol, triglycerides, and glucose metabolism. Over time this can lead to deterioration of health and wellness.

2 - Talk to Your Medical Provider

If you are on an obesogenic medication, know your numbers and discuss routine monitoring of labs with your healthcare professional to identify out-of-range numbers earlier. Early identification promotes earlier intervention, which prevents progression of chronic diseases and negative sequelae that can stem from silent damage to major organs. 

3 - Consider a CGM for Weight Loss

In some cases, continuous glucose monitoring may be considered to get a closer look at how your body reacts to the medication when paired with nutritional intake. This may also assist with diet modification to help better regulate the hormones in your body when taking an obesogenic medication and potentially lose the extra weight <sup>23</sup>.

Sometimes, even the best dietary and exercise changes cannot outrun the effects of a medication - and that’s okay too. Talk to your healthcare professional every step of the way. Don’t make any changes without getting their perspective specific to your unique medical history. 

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About the Author

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Dr. Cathleen McKnight is a licensed nurse practitioner in Ohio.
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Please note: The Signos team is committed to sharing insightful and actionable health articles that are backed by scientific research, supported by expert reviews, and vetted by experienced health editors. The Signos blog is not intended to diagnose, treat, cure or prevent any disease. If you have or suspect you have a medical problem, promptly contact your professional healthcare provider. Read more about our editorial process and content philosophy here.

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