Alert: 8 Prescription Drugs That Silently Cause Weight Gain

Obesity or overweight is a potential healthcare problem affecting 39% of adults all over the globe.

It is characterized by excessive accumulation of fat in our body specially in the abdomen, waist and hip area.

This leads to further disease risks like type 2 diabetes, hypertension, cardio-vascular disease, increases blood glucose and cholesterol level.

A definitive way of achieving weight loss is proper exercise regime and well-planned diet. Mere weight reduction isn’t enough if we are unable to sustain it.

Thus an important precautionary measure is weight maintenance.

However there can be certain factors that go unnoticed and impede weight loss efforts.

Certain types of drugs like anti-depressants, anti-epileptic drugs, psychotropic drugs cause silent weight gain.

8 Prescription Drug Types That Silently Cause Weight Gain

Here is a list of common drugs that despite of being therapeutic have an undesirable side effect- weight gain.

1. Anti-diabetes therapy

This class of drugs is used as a treatment for type 2 diabetes. Hence, the name anti-diabetes.

It enhances the lipid profile and reduces the blood glucose level.

But a major problem of these group of drugs is their propensity of weight gain. As the majority of people suffering from type 2 diabetes are obese, this is a potential hazard.

This category includes a range of drugs like Sulfonylureas, Meglitinides, Biguanides, Glucosidase inhibitors, insulin analogs etc., the individual effects of each on weight gain are discussed later.

Insulin Secretagogues

medicinesThis category of drugs is used for enhancing the secretion of insulin from the pancreas of patients suffering from type 2 diabetes. They include 2 drugs sulfonylureas and meglitinides.

Several combination therapies with sulfonylurea shows its potential effect in weight gain.

A trial illustrated this effect. A combination of sulfonylurea and metformin showed a 40% weight gain in a year.

Data analysis from 14 trials showed that sulfonylurea causes greater weight gain than metformin ( a drug decreasing glucose production and increasing insulin sensitivity).

Data analysis from 15 trials shows that meglitinides have greater weight gain propensity than metformin, 3 kg in 3 months to be precise.


This class of drug lowers blood glucose level. It is one of the foremost treatment for type 2 diabetes.

However, recently it has been associated with weight gain.

The weight gain associated with this drug can be lowered by low-calorie low sodium diet.

Insulin Analogs

This class of drugs is the most effective anti-diabetic therapy. These are insulin analogs having similar function as naturally secreting insulin.

This includes reduced glucose formation in the liver and increased glucose uptake by the tissue thereby lowering the overall blood glucose level.

However, they are a potential cause of weight gain.

Analysis from 14 clinical trials illustrate that the efficacy of long-acting basal insulin analog is similar to naturally secreted insulin.

However, the weight gain potential varies between the two.

Another 112-month study on type 1 diabetes patients showed the insulin analogs having slightly less weight gain potential than normal insulin.

What does this mean? Evidences from the above studies points out in one direction that several varieties of anti-diabetic therapy has small to moderate amount of weight gain capacity. This is due to increased insulin secretion which leads to increased fat deposition.

2. Steroids

These are glucocorticoids by nature which affects hormonal secretion from the hypothalamus, pituitary gland or the adrenal gland.

They are used as a treatment for inflammation. As they influence the hormonal secretion their prolong use can lead weight gain.

A year long study showed greater than 10% weight gain in one fifth of the patients (suffering from an inflammatory disease) treated with glucocorticoids (GC) .

Glucocorticoids has been known to enhance weight gain by over- expressing an enzyme in white fat cells.

25mg daily consumption of Glucocorticoids for 7 days enhances serum leptin( satiety hormone which controls hunger)level and appetite.

A recent study showed this effect of Glucocorticoids can be greatly reduced by using a mineralo-glucocorticoid receptor.

This receptor binds to Glucocorticoids and considerably reduces its weight gaining potential.

What does this mean? From the above points it is clear that steroid hormones are potential cause of weight gain. This is due to their effect on appetite and expression of white fat cells.


This class of drugs is primarily used for different psychological disorders like schizophrenia, bipolar disorder.

Their potential area of the target are messenger hormones of the brain like dopamine, serotonin etc.

Their prolong use is associated with substantial weight gain. Drugs like clozapine and olanzapine are causes of weight gain.

A clinical study involving atypical anti-psychotics olanzapine , clozapine and risperidone showed olanzapine having more weight gaining capacity than the other two.

Results were analyzed from weekly measurements of BMI.

A meta analysis from 307 studies of varying durations of 6 weeks, 16 weeks, 38 weeks and more than 38 weeks concluded that all antipsychotics causes weight gain.

A 3-5 week duration clinical study of 500-600mg of daily clozapine consumption showed a cumulative weight gain among 50% of patients.

What does this mean? Antipsychotic drugs have a very significant tendency of causing weight gain as a side effect in treatment of psychiatric disorders.This effect is because of increased appetite and food cravings.

4. Antidepressants

This class of drug is used for the treatment of depression and anxiety. Their mode of action is by affecting the serotonin hormone secretion.

Tri-cyclic antidepressants cause more weight gain than serotonin inhibitors.

They have similar effects on the glucose and lipid profile of the body as shown by anti-psychotics but to a lesser extent.

A 4.8 year long follow up study showed this effect. People with regular consumption of anti-depressants showed 2.5kg self reported weight gain whereas people without treatment showed 1. 4kg self reported weight gain.

Meta-analysis of different studies illustrated the varying weight gain potential of anti-depressants. amitriptyline, mirtazapine, and paroxetine have the greatest weight gaining potential.

On the contrary , fluoxetine and bupropion are associated with a smaller degree of weight gain.

Another study highlighted this same weight gain effect of newer anti-depressants like paroxetine, mirtazapine etc.

What does this mean? This highlights the potential weight gaining capabilities of certain anti-depressants specially tri-cyclic anti-depressants. However their mode of action isn’t well illustrated. One school of thought is depression in some people causes weight loss due to excessive anxiety. These people when treated with anti-depressants gain weight. More or less these drugs affect brain chemicals which control mood and appetite simultaneously.

Prescription Drugs That Silently Cause Weight Gain

5. Antiepileptics

This class of drugs are designed as a treatment for epilepsy.

They have varying potential with regards to weight management.

Some causes weight gain while others are weight neutral.

Valproate, pregabalin and vigabatrin are the anti-epileptics responsible for weight gain.

12 months analysis of different anti-epileptics showed valproate, levetiracetam to cause maximum weight gain and carbamazepine, lamotrigine not associated with weight gain.

Another 6-8months duration study illustrated 66.7%patients on carbamazepine and 60% patients on valproate showed weight gain.

6months study shows this valproate induced weight gain may be due to increased serum insulin and serum glucose level and an increased urge for food consumption.

Carbamazepine induced weight gain is due to increased food intake, overeating and fat deposition. All this resulted an increase of weight from 7 to 15kg in 2 months.

A similar 6 month trial showcased moderate weight gain effect of valproate, gabapentin and greater weight gain effect of pizotifen, amitriptyline

A 12 month trial shows gabapentin has moderate weight gain effect at the starting which normalizes after 6-9months.

In combination with other drugs, gabapentin causes greater weight gain.

What does this mean? Thus it is can be concluded from the above points that anti-epileptics cause substantial weight gain and should be avoided to a larger extent.This effect is due to increased level of fat deposition and increased hunger leading to over-eating.

6. α-Adrenergic Blocker

These are drugs which mimics hormone signalling molecule epinephrine and norepinephrine which further leads to muscle and blood vessel constriction.

This class of drug used for blocking adrenergic receptors (receptors for a sympathetic nervous system like epinephrine, dopamine etc) and thus used as a cure for hypertension and prostrate hypertrophy.

A Cochrane review analysis from different short –term randomized trials highlights this phenomenon.

Amongst the adverse side effects, the study talks about weight gain.

A gene study revealed that the presence of alpha adrenergic blocker genotype results in 10% more weight gain than in populations without this gene.

What does this mean? Alpha adrenergic blockers are drugs used to treat hypertension and prostate hypertrophy. They cause weight gain by affecting genes involved in fat metabolism.

7. β adrenergic blockers

These are drugs which bind to a type of adrenergic receptors called beta- adrenergic blockers.

They inhibit epinephrine, norepinephrine and other chemical messenger (molecules transmitting impulses between various components of the nervous system) of the sympathetic nervous system.

This class of drugs are used for hypertension and coronary heart disease treatment.

They can lead to 1-2kg of weight gain.

They cause a 10% reduction in metabolic rate which is the primary reason for weight gain. Most studies showcase a 1.2 kg weight gain.

A year long follow up study has found this weight gain effect is greater in non-edematous (accumulated fluids in cells and tissues) patients than in edematous patients.

What does this mean?
Beta adrenergic blockers are prescribed for cardiovascular problems and these can cause weight gain by interfering in the rate of metabolism.

8. Antihistamines

medicines2Histamine is a nitrogenous compound released by our immune system when a foreign body attacks our body.

This is the primary cause of allergy.

Anti-histamines are compounds which bind to histamines and blocks their action.

This class of drug is used as a treatment for different types of allergies. Their target of action is the allergy causing blood component histamine.

However, some of them can cause weight gain.

H1 antihistamine is associated with obesity which can be seen as a greater hipline waistline and BMI measurement in persons availing those drugs.

H1 antihistamine causes weight gain by stimulating fat accumulation and appetite on the one hand and reducing the energy expenditure on the other hand.

Another meta analysis of different drugs effecting weight gain showed non-significant results in case of anti-histamines.

What does this mean? Anti-histamines lower energy expenditure and enhance hunger and fat accumulation, thus leading to weight gain.


These are a few of the drugs that may serve as hidden agents in your lifestyle that are responsible for weight gain.

Its best to consult doctors for alternatives to these medications which do not cause as significant weight gain as these.

Change in dietary habits and regular exercise could also help in offsetting the weight gain caused by medications.


Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.