Medication and Weight Gain

Medications, also known as medicines, pharmaceuticals or prescription drugs are an extremely  important part of modern medicine as they can help manage, cure or treat specific conditions and can be life-saving.

Alongside the beneficial effects also comes side effects or ‘adverse reactions’. Side effects can range from mild to life threatening conditions, although these thankfully are rare. Unfortunately one side effect of some commonly prescribed medications is weight gain.

In particular, weight gain can be a side effect of medications prescribed to treat the common conditions hypertension (high blood pressure), Type 2 diabetes, and depression. Some antipsychotics, antiepileptics, antihistamines and neuropathic agents also lead to weight gain.  

Diabetes medications

Diabetes is characterised by high levels of sugar (glucose) in the blood. There are several things that can improve blood glucose levels including weight loss, activity and diet. Medication can also help to do this. 

Different diabetes medications work in different ways. For example, they can encourage the body to produce more insulin, improve your sensitivity to insulin or offer insulin itself as a treatment. Some common medication for Type 2 diabetes – insulin, sulfonylureas and thiazolidinediones – have been associated with weight gain. 

When you take insulin or take medications that encourage its production, if you consume more carbohydrate than you need, your cells will take on more glucose and excess will be stored as fat. Therefore it is important to follow a healthy diet and lifestyle to prevent weight gain which could worsen diabetes control in the longer term. 

Another common adverse effect of some diabetes medications is hypoglycaemia (low blood glucose levels). Intake of sugar or carbohydrate is required to correct this to increase blood glucose levels but in doing so extra calories are required so frequent correction of low blood glucose levels by consuming additional sugary or carbohydrate snacks can contribute to weight gain. 

It is important not to stop taking diabetes medication even if you are gaining weight. If weight is a problem when taking these medications a review of your dietary intake and physical activity levels should be undertaken. Being aware of the effects of the medication can help you to lose weight or maintain the weight you are at. 

For some people, Type 2 diabetes can be controlled and improved via weight loss itself. For some people, losing 10-15kg can put Type 2 diabetes into remission, reducing the need for medications that may promote weight gain (1); but reductions in medications can be seen even if remission isn’t achieved itself.  

Antipsychotic medicines 

As well as treating the conditions they are indicated for, some antipsychotic medications such as clozapine and olanzapine, among others, can affect neurotransmitters that are associated with appetite control and energy metabolism and can lead to weight gain. The rate of weight gain when on these medications is usually rapid at first and then plateaus, however individuals do seem to continue to gain weight over time (2). 

Weight gain with these medications can reduce compliance to taking the medication which, if suffering from a serious psychotic condition, has the potential to be dangerous. Early intervention in these situations can be important, changes to diet and lifestyle have been shown to promote weight management, reduce cardiovascular risk and improve quality of life in patients with these conditions (3,4). 

Antidepressant medicines 

Major depressive disorder affects 23% of the global population and antidepressants are the first line treatment option. Weight gain is a significant adverse effect of these medications. It is thought that their action on serotonin receptors may increase appetite and suppress satiety. 

This weight gain effect can be a significant barrier to people continuing to take these medications as it can impact quality of life, self-esteem as well as being a risk factor for obesity, cardiovascular disease and diabetes. Balancing the antidepressant benefits with weight gain is a challenge but it is important for people suffering with this condition (5). Participation in a weight management program can promote weight loss or maintenance of a healthy weight in patients taking medication for mood disorders (6).