How Fast Do GLP-1 Drugs Suppress Appetite?

It can be an exciting feeling to know that a GLP-1 agonist may help you reach your weight loss goals, especially if other methods that you’ve tried in the past haven’t worked.

So, how long does it take for the medication to work? It may be a good idea to manage your expectations, says obesity medicine subspecialist W. Scott Butsch, MD.

How long does it take for GLP-1s to suppress appetite?

For people who use one of the two new GLP-1s, semaglutide (Wegovy™) or tirzepatide (Zepbound®) to lose weight, the results can vary from person to person.

“These once-weekly injections usually reach their maximum effectiveness in about 72 hours,” explains Dr. Butsch. “The effects can be experienced within the first few days, whether that’s an effect on your appetite or side effects like nausea, vomiting or diarrhea.”

These two new drugs are part of a larger class of GLP-1 drugs that mimic the gut hormone GLP-1, which is made naturally in your intestines and brain. Not only can it help with your insulin response to control blood sugar (and diabetes), but it can also control body weight (and fullness) by targeting specific areas of your brain. It can also slow how quickly your stomach empties itself after eating (affecting how full you feel after a meal).

But you may not notice a change to your appetite after your first dose, cautions Dr. Butsch. It may take a few weeks.

“We know with medications that it can take several doses to have a full effect,” he says.

Factors that can influence how long it takes to work

Each person will respond differently to the medication. Factors that can impact how fast they start working include:

• Diet
• Exercise
• Metabolism
• Menstrual cycle
• Sleep
• Stress levels

Another factor to take into consideration? The dosage.

“The initial dose of the medication may not have any effect,” clarifies Dr. Butsch. “You may have to keep increasing the dosage before you see an effect.”

It all goes back to managing your expectations and knowing it may take time to figure out the best dose for you.

“This has occurred in some of my patients, where the drug has no effect,” he continues. “They get frustrated because it takes several months to escalate the dose to the highest level and see the benefits.”

How long does it take to start seeing weight loss results?

There’s no set timeline for when you’ll start seeing results. It’s an individualized and unique experience for each person.

“We see in clinical trials that there’s a variation in the amount of weight someone loses, a variation in their appetite and a variation in unwanted side effects,” says Dr. Butsch. “Therefore, it’s hard to know exactly what the benefits will be and when you first see a patient.”

But he adds that research shows a connection between how you initially respond to GLP-1s and how it may benefit you long-term.

“If you lose more than 5% of your body weight in the first three to four months on an obesity medication, then you’re more likely to maintain that body weight after 12 months,” reports Dr. Butsch. “Similarly, another recent study with tirzepatide shows that if someone loses 10% or 15% of their body weight by six months, they’re more likely to keep it off after one year.”

Bottom line?

While ongoing research will continue to shed light on how fast GLP-1s work, Dr. Butsch says there are steps you can take now to help the medications work their best.

“The important thing is to continue to focus on making lifestyle modifications — whether that’s improving sleep, a healthier diet or physical activity — as you and your doctor decide if this medication is going to be effective,” he states. “That may take several months as the drug doses are adjusted.”