June 6, 2022 -- A drug recently approved for type 2 diabetes in the United States is also very effective for treating obesity and has shown better weight loss than any previous medication, according to results from a new clinical trial.

In the new study -- which focused on patients with obesity but without diabetes -- more than 90% of patients taking the highest dosage of tirzepatide lost of at least 5% of their weight, says endocrinologist Ania M. Jastreboff, MD, the doctor who led the study.

And 40% of individuals on this highest dose lost a quarter of their body weight, she says.

“If you respond to this medication, you will feel full earlier, you won’t want to go back for seconds, and you may eat smaller amounts more often,” Jastreboff told a press conference at the annual scientific sessions of the American Diabetes Association, where the trial results were presented on Saturday.

But Jastreboff, who is also director of Weight Management & Obesity Prevention at Yale School of Medicine, stressed that not everyone can tolerate tirzepatide as it can cause nausea, among other side effects.

Patients will also need to take any obesity medications long-term, in the same way that people take pills for life to reduce their cholesterol or high blood pressure.

"If you stop the anti-obesity medication then the body fat [will go back up], so this necessitates long-term treatment,” Jastreboff says.

And because obesity is one of the biggest risk factors for developing type 2 diabetes, it makes sense to try and treat obesity first, she says.

"Perhaps we can prevent diabetes by treating obesity head-on."

'A New Era' in Obesity Treatment?

Tirzepatide was approved for type 2 diabetes under the trade name Mounjaro last month, but the manufacturer, Lilly, will still have to submit an additional application to the FDA for use of the drug in those with obesity.

Other experts at the meeting said the results seemed to suggest that the weight loss seen with tirzepatide is greater than that seen with semaglutide (brand name Wegovy), an obesity drug approved in the U.S. a year ago, also given as a once-weekly injection, and hailed as a “gamechanger” for weight loss at the time it was approved.

But the two drugs have not been directly compared, doctors said.

These weight loss results "put tirzepatide squarely in the range of weight loss achieved with bariatric surgery," says Louis J. Aronne, MD, a co-researcher on the trial. Aronne is also the director of the Center for Weight Management and Metabolic Clinical Research of Weill-Cornell in New York City.

Another expert agreed. Despite the lack of direct comparison, the findings indicate that "tirzepatide causes more weight loss than semaglutide," and it provides "an opportunity to meet or exceed" the weight loss effects of bariatric surgery, says Lee M. Kaplan, MD, who was not involved in the study.

The results are "amazing," and propel the weight-loss field into "a new era of obesity treatment," says Kaplan, director of the Obesity, Metabolism and Nutrition Institute at the Massachusetts General Hospital in Boston.

Jastreboff agrees.

"Starting last year with semaglutide and now tirzepatide, these agents are more highly effective than any other [previous] weight loss agents, and it’s a new era for our patients and for physicians caring for patients with obesity. We will have more tools,” she told the media briefing.

“There is not one type of obesity,” she said, noting that what works for one patient doesn’t necessarily work for another.

“When patients come to see me in clinic, they have faced so much stigma. They have so much self-blame, so I always ask them to share their struggles and successes and I tell them, ‘This is not your fault. This is biology, your body does not want you to starve.’ We live in this environment with highly palatable foods that are inexpensive and available all the time, and we have sedentary, stressful lives.”

Better Cholesterol and BP, Trimmer Waists

In the trial – which included 2,539 adults who had an average weight of 231lb and a BMI of 38 – participants lost, on average, between 35 to 52 pounds when receiving a weekly injection of the drug over 18 months, compared to a loss of just 5 pounds in those who got the placebo, or dummy, injection. All participants were also given regular lifestyle counseling sessions, delivered by a dietitian or a qualified health care professional, to help them stick to healthful, balanced meals which cut 500 calories per day from their diet, and at least 150 minutes of physical activity per week.

At the end of the study, patients had lost, on average, 35.5lbs on a 5mg dose of tirzepatide, 48.9lb on a 10mg dose, and 52lbs on a 15mg dose, compared with a loss of 5.3lb with placebo.

Nearly everyone taking tirzepatide also had improvement in blood sugar, blood pressure, and cholesterol levels. It trimmed the participants waists by 5.5 inches in those taking the 5mg dose, and by 7.2 inches in those taking the 15mg dose, compared with 1.5 inches in those who received placebo.

About 15% of participants who received tirzepatide left the trial, about a third because of the gastrointestinal side effects. Meanwhile, 26% of trial volunteers who received placebo injection dropped out.

Cost a Key Issue

One big issue will be access to these medications, which come with hefty price tags in the U.S., doctors told the press briefing.

The retail cost of semaglutide for obesity exceeds $1,000/month, and it is thought that the price of tirzepatide will be similar.

“Right now the biggest barrier is cost – we don’t know what the cost is going to be yet [for tirzepatide if approved for obesity] but if we look at costs of other obesity drugs, this is probably going to be at a level that most people without adequate insurance are not going to be able to [access],” Robert H. Eckel, MD, of the University of Colorado at Denver, Aurora, tells WebMD.

That said, Aronne says that his numbers showed that during the first months that semaglutide was available for weight loss, the number of U.S. prescriptions written for branded anti-obesity medications roughly doubled, a spike that seemed mostly driven by the introduction and growing use of semaglutide.

“As healthcare providers, we do whatever we can to try to help patients access these drugs. I testified in our state senate asking them to approve obesity medications and bariatric surgery, which I believe should be covered by private insurance as well as Medicaid,” Jastreboff says.

The full findings were also published in the New England Journal of Medicine.