Drugs’ Side Effects Can Be Different If You Carry Extra Weight

Drugs' Side Effects Can Be Different If You Carry Extra Weight
Drugs' Side Effects Can Be Different If You Carry Extra Weight
Emma Yasinski
Emma Yasinski Staff Writer

Does a person’s higher weight impact how effective a recommended drug dosage may be?

Researchers found, for example, that common versions of Plan B (levonorgestrel), the morning after emergency contraceptive pill, was less effective in women who weighed more than 165 pounds, and not effective at all for those over 175. Last year, that fact caught a wave on social media after TikToker @anadelrey.xo shared a video suggesting that anyone over 150 to 155 pounds should take two pills instead of one. Note: Specialists do not recommend taking two pills. Instead, they suggest the alternative medicine Ella (ulipristal). 

@anadelrey.xo Reply to @yanieboyd what if I don’t wanna be 155 😭 plan b is meaty-phobic 🤚🏽 #planb #TakeTheDayOffChallenge #BenefitOfBrows ♬ eredeti hang – Petra Horváth

There’s conflicting evidence about whether the assertion is true. In 2013 and with support from regulators, European manufacturers changed the label to reflect the risk of inefficacy in patients with higher weights. Three years later, the Food and Drug Administration (FDA) announced that the evidence of the drug being less effective in women with obesity was inconclusive. Carrying extra fat tissue can change how your body reacts to some drugs, and a lot more research needs to be done to determine which treatments are affected and how doses should be adjusted.

How Excess Fat Impacts a Drugs Side Effects

Carrying extra weight impacts the way your body responds to different drugs in a variety of ways. For some drugs, it may increase their efficacy and side effects; for others, it may lessen them. If you’ve been prescribed more than one drug, excess fat can also impact how they interact with each other. Talk to your healthcare provider about how your dose may need to be adjusted based on your body’s composition, especially if you’re experiencing side effects. 

Some of the most common ways fat can influence drugs in your body are by: 

  1. Slowing Drug Uptake

Medication needs to cross blood-brain barriers, fat barriers and other barriers to reach the correct destination,” explains Hector Perez, MD, a surgeon at Renew Bariatrics in Tijuana and Cancun, Mexico. If there’s extra fat tissue, this journey can take longer. You may need a higher drug dose to realize the same effect as someone who doesn’t have excess fat.

  1. Increasing Drug Storage

Some drugs and supplements are stored in water, others are stored in fat. If you have extra fat tissue, the types of drugs stored in fat will stay in your body longer. That means that as you take more doses, the amount of drugs in your body can build up to higher levels than you intended, because there’s extra leftover from previous doses. That can cause more intense side effects.

  1. Retarding Drug Clearance Through Liver

“Medications should be adjusted in liver and kidney disease. The medication class that comes to mind are the antipsychotics for schizophrenia and other unspecific psychosis and anti-seizure medications,” says Joseph Claiborne III, MD, a physician with the Methodist Family Health Center in Preston Hollow, Texas. Most medicines are metabolized through your liver. Carrying extra fat can cause a buildup of fat on the liver that can reduce its efficiency with which your body breaks them down.

Some drugs and supplements that might be metabolized differently based on your body weight include:

Before starting a new drug, it’s important to ask your doctor how your body’s composition might affect how well that drug works and how it might raise or even reduce your likelihood of experiencing side effects. For many conditions, regular exercise and a healthy diet can help reduce your symptoms. However, if you do lose or gain weight during the course of treatment, be sure to check in with your provider to evaluate whether a new dose or even deprescribing—reducing the number of drugs you take—might be called for.

How Fat Is Also a Gender Issue

Women noted adverse effects from medicines nearly twice as often as men do, according to a 2020 study, published in the Biology of Sex Differences. In 2021, MedShadow reported that there are numerous differences in the way men and women metabolize drugs, but one important one has to do with their differing body compositions. Women naturally carry more fat tissue than men and that can make it harder for a drug to reach its intended target, or it could keep that drug in your body longer. Fat plays an important role in how our bodies process and store the drugs we’re prescribed and can be an important variable to consider when our healthcare providers are determining the optimal doses for treatment. 

How Doctors Can Be Dismissive of Overweight and Obese Patients

Having obesity has for years made it harder for some patients to receive high-quality care from their physicians.Research has shown that doctors communicate differently with overweight patients, spending less time expressing empathy and concern, for example. In March 2020, doctors published a statement in Nature, calling for an end to weight stigma.  At times, doctors tell the patient the problem will go away if they lose weight, only to find out later that the patient has had a serious illness that could not be cured by weight loss. For example, in 2016, STAT reported a story about a woman who saw 11 different doctors who all told her to lose weight. She was later diagnosed with lung cancer that was so severe she had to have an entire lung removed.

If your physician dismisses your concerns, it’s time to find a new provider.  


DISCLAIMER: MedShadow provides information and resources related to medications, their effects, and potential side effects. However, it is important to note that we are not a substitute for professional medical advice, diagnosis, or treatment. The content on our site is intended for educational and informational purposes only. Individuals dealing with medical conditions or symptoms should seek guidance from a licensed healthcare professional, such as a physician or pharmacist, who can provide personalized medical advice tailored to their specific circumstances.

While we strive to ensure the accuracy and reliability of the information presented on MedShadow, we cannot guarantee its completeness or suitability for any particular individual's medical needs. Therefore, we strongly encourage users to consult with qualified healthcare professionals regarding any health-related concerns or decisions. By accessing and using MedShadow, you acknowledge and agree that the information provided on the site is not a substitute for professional medical advice and that you should always consult with a qualified healthcare provider for any medical concerns.

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