For millions of seriously overweight Americans, popping a pill to get to a healthier weight more quickly might seem appealing. But for many people, weight-loss drugs could dangerously change the rhythm of their heartbeats.
A variety of weight-loss medications are available. Here's what you need to know about weight-loss drugs and your heart rhythm.

Weigh the Medication Risks and Benefits  

People who are overweight or obese are at risk for serious health problems, including type 2 diabetes, high blood pressure, heart disease, and stroke. In addition, extra weight makes your heart work harder. 
Excess weight can cause your heart rate to increase, and an increased heart rate can eventually weaken your heart muscle and lead to congestive heart failure, explainedKevin R. Campbell, MD, an assistant professor in the division of cardiology at the University of North Carolina School of Medicine. A very fast heart rate can also cause your blood pressure to drop too low, resulting in blackouts. 
Taking a weight-loss drug can lead to similar heart conditions. That's because weight-loss medications often contain stimulants, which help you be more alert and less interested in food, Dr. Campbell said. However, when a drug promises to speed up your metabolism, it may increase your heart rate. In people susceptible to atrial fibrillation — the most common type of arrhythmia, or irregular heartbeat — these types of stimulants may trigger an afib episode. 
However, weight-loss medication may be appropriate for some people. 
study published in 2013 in Obesity Reviews found that people who are obese have a hard time resisting food cues — familiar smells or visual images that cause a chemical process in the brain, similar to a drug addiction, and increases their desire for food. Medication may be able to change the way the brain receives the information and help you eat less. 
“Medications to control appetite are important to keep a person on track,” said Sue Decotiis, MD, a weight-loss expert in New York City. That's especially true in the beginning of a weight-loss effort and again for up to three years after a significant weight loss, "when appetite is increased and needs to be tamed," she said.  

Know the Weight-Loss Drug Options

Weight-loss drugs approved by the Food and Drug Administration have been strenuously tested and are generally quite safe, Dr. Decotiis said. However, if you're taking other medications or have certain pre-existing conditions, such as uncontrolled high blood pressure or cardiovascular disease, your risk for adverse side effects can increase. 
If you're considering using a weight-loss drug or supplement, it's important to first learn as much as you can.
For instance, some popular over-the-counter weight-loss drugs, such as Alli and Dexatrim, may help with weight loss in the short term, but the weight usually comes back once you stop taking the medicine. Dexatrim contains stimulants, which can cause problems for people prone to afib. Alli is a lipase inhibitor, a type of drug that helps with weight loss by preventing the body from absorbing certain types of fat — which may sound like a good idea until you consider side effects such as gas with oily spotting, diarrhea, and abdominal pain. 
“The oldest group of medications includes phentermine, diethylpropion, and phendimetrazine, which work by stimulating the adrenergic nerves to turn off hunger,” Decotiis said. These medications may be habit-forming and should be used only as directed. Common side effects include dry mouth, nausea, jumpiness, and irritability. Serious side effects vary by drug but can include depression, heart palpitations, fast or irregular heartbeat, increased blood pressure, dizziness, tremors, chest pain, and difficulty breathing.  
More recently, the FDA approved two medications intended for long-term use: Belviq (lorcaserin) and Qsymia. These prescription weight-loss drugs work by manipulating receptors in the brain that decide how you respond to hunger. Belviq activates a serotonin receptor that can help you eat less by making you feel full after eating smaller portions of food. Qsymia, which is a combination of phentermine andtopiramate (a drug used for seizures and migraines), works by shutting off hunger desires deep in the brain and also affects the way the gastrointestinal tract responds to food, Decotiis said. 
Although both medications show promise, they carry strong warnings about potential side effects, including heart problems:
  • Belviq can cause your heart rate to slow and lead to valvular heart disease and congestive heart failure.  
  • Qsymia can increase your resting heart rate. It also can cause serious eye problems and lead to severe birth defects if you are pregnant or become pregnant while using the medication.

The Bottom Line on Weight Loss

Before resorting to weight-loss medication and its potential risks, consider safer options, like modifying your diet and adding exercise to your daily routine. Whatever method you choose to lose weight, be sure to work closely with your doctor and safeguard your heart health.