The culprit behind your pesky weight gain could be lurking in your medicine cabinet.
Prescription medications often come with long lists of side effects, from infections to rashes to suicidal thoughts.
And while it’s well known that some, like steroids, can make you pack on the pounds, other commonly prescribed medicines, like some painkillers, may come as a surprise.
Pharmacists have revealed to DailyMail.com the commonly taken drugs that you never knew were fattening — including some that could increase your waistline by up to five pounds in a couple of months.
Pharmacists told DailyMail.com which medications could be behind your pesky weight gain
Antidepressants
Antidepressants have been blamed for a host of side effects, from insomnia to headaches and even killing patients’ sex lives.
However, some classes of these drugs have also been shown to lead to weight gain.
Dr HaVy Ngo-Hamilton, clinical consultant at BuzzRx and pharmacist at the University of Minnesota Medical Center, told DailyMail.com that these are largely tricyclic antidepressants, an older class of drug than the more common selective serotonin reuptake inhibitors (SSRIs).
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‘Tricyclic antidepressants, or TCAs, are the class of antidepressants that cause the most weight gain,’ she said. ‘When it comes to weight gain, I try to stay away from the tricyclic antidepressants as much as possible.’
She noted that TCAs are prescribed less often than newer SSRIs due to more intense side effects, including insomnia, bed-wetting, and chronic pain conditions such as fibromylagia.
Some of the most common examples of these include amitriptyline and nortriptyline.
Dr Ngo-Hamilton estimates that a patient on these drugs may gain about two pounds per month.
However, she also noted that antidepressants could lead to weight gain due to mood improvements.
A patient may have had little desire to eat, so as the drugs regulate their production of happiness hormone serotonin, they could increase their appetite.
Antipsychotics
In a similar vein, antipsychotic medications like clozapine, risperidone, and olanzapine may be prescribed for patients with severe mention health conditions such as schizophrenia and bipolar disorder, as well as some with dementia.
‘Antipsychotics decrease the metabolic rate in our body,’ Dr Ngo-Hamilton said.
This is the amount of energy you expend while at rest. Someone with a slower metabolic rate may then burn fewer calories, as the body converts food into energy at a slower pace.
Dr Ngo-Hamilton noted that these drugs can also lead to sedation and lethargy, making a patient less likely to exercise or maintain a proper diet. Some of this weight gain could also be due to urinary retention, a known antipsychotic side effect that makes the kidneys unable to properly remove toxins and waste from urine.
She pointed to clozapine (Clozaril) as the most common culprit in this category.
Anticonvulsants
Medications that reduce the frequency of epileptic seizures and nerve pain also may cause weight gain in some patients.
Dr Ngo-Hamilton pointed specifically to gabapentin, which combats seizures by decreasing abnormal signals in the brain, as an example, but other drugs like pregabalin (Lyrica) and carbamazepine (Tegretol), prescribed to those with spinal injuries, could cause similar effects.
However, ‘the mechanism for anticonvulsants on how they cause weight gain is unclear,’ Dr Ngo-Hamilton said.
Recent research has pointed to several theories, including increased appetite, slowed metabolism, retaining fluid, and the drug disrupting hunger and satiety hormones.
Dr Ngo-Hamilton estimates that patients on these drugs can gain roughly five pounds in the first few months of taking them.
Beta blockers
Beta blockers are medications meant to lower blood pressure and block the effects of the hormone epinephrine, or adrenaline. This helps improve blood flow and lower heart rate.
Dr Ngo-Hamilton noted that several ‘older’ beta blockers like metoprolol, atenolol (Tenormin), and propranolol have been shown to cause weight gain.
However, like anticonvulsants, the exact mechanism is still unclear. Dr Ngo-Hamilton noted that one theory is these drugs decrease metabolic rate, similar to antipsychotic drugs.
Additionally, some evidence suggests that because beta blockers decrease blood pressure and the amount of blood the heart pumps, patients may become fatigued and have a difficult time working out.
Dr Ngo-Hamilton estimates a two- to three-pound weight gain in the first six months of taking one of these older beta blockers.
Corticosteroids
Corticosteroids are drugs taken to lower inflammation in the body.
The most common examples are prednisone and dexamethasone, which work by mimicking the effects of the hormone cortisol – which the body releases when it’s stressed or injured – to lower inflammation.
These are different than anabolic steroids, which increase testosterone levels to enhance athletic performance.
Corticosteroids are generally only taken for a few days at a time, though they may be prescribed long term for certain issues like autoimmune conditions.
‘I’m not worried that these might cause weight gain in someone taking them for a few days. It’s the people who have to take steroids chronically who experience weight gain,’ Dr Ngo-Hamilton said.
She noted that a common side effect is ‘Moon Face,’ which leads to the face becoming round, full, and puffy. And mimicking cortisol can also lead to increased appetite.
Dr Ngo-Hamilton noted that a patient taking steroids for a year could gain up to 10 pounds.
Birth control shots
Hormonal birth control has long been demonized for causing weight gain, though Dr Ngo-Hamilton cautions that most contraceptives do not pack on the pounds.
‘Women on contraceptive birth control that experience weight gain is mostly water weight,’ she said. ‘That is the result of fluctuations in estogren levels.’
However, one form of birth control called Depo-Provera – the Depo Shot – has been shown to cause weight gain. This is an injection containing the hormone progestin and given once every three months.
The medication’s label states that almost 38 percent of women in clinical trials dained more than 10 pounds after using the contraceptive for two years.
Additionally, one older study found that the medication caused an average weight gain of 20 pounds over 18 months.
Dr Ngo-Hamilton estimates most patients would gain four to five pounds per year.
Statins
About one in five Americans take statins, which some research suggests could lead to weight gain
Roughly 47million Americans take statins, a medication aimed at lowering cholesterol levels, making it one of the most popular drugs in the US.
Statins work by limiting the production of ‘bad cholesterol’ — low-density lipoprotein (LDL) cholesterol — which can harden and narrow the arteries, and increase the risk of cardiovascular disease.
‘These can cause a small amount of weight gain, but it’s very uncommon,’ Dr Ngo-Hamilton said.
A study published in JAMA Internal Medicine, for example, found that patients taking statins gained six to 11 pounds compared to those who didn’t take them over a 10-year period.
However, much of the evidence is limited, Dr Ngo-Hamilton cautions. She also notes that the cheap drugs, which lower cholesterol and reduce the risk of conditions like heart disease, are not worth quitting over potential weight gain.
‘The benefits definitely outweigh the risk of small amounts of weight gain,’ she said.
