Another week, another obesity drug tested – but a new one by the US pharmaceutical giant Lilly may prove to be promising, with people who had weekly injections of the drug losing 22.5 percent of their body weight on average.

Obesity is at global epidemic levels and spans many different ages and socioeconomic groups. There are many different weight loss programs and drugs available on the market, and new technologies and drugs are constantly being created and tested to help those who want to lose weight.  

The human body is a very complex system and when the body needs energy (calories) it releases the hormone ghrelin, which in turn makes us feel hungry. After we have consumed a delicious meal, the body then produces less ghrelin and releases hormones like GLP-1 (glucagon-like peptide-1), PYY (peptide YY), and leptins. These hormones help us feel satiated. 

When trying to lose weight, the satiety hormones actually decrease and the hunger hormones increase, making it difficult as it leads to the constant gnawing of hunger.

The new drug from Lilly is called tirzepatide, combining two synthetic hormone mimics; GLP-1 and GIP (glucose-dependent insulinotropic polypeptide). In preclinical models, GIP seems to increase energy expenditure and decrease food intake. Combining GIP with GLP-1 receptor agonism could result in greater weight loss.   

The company presented its study results on April 28, 2022. This study was the first phase 3 clinical trial to evaluate the efficacy and the safety of the drug in adults who do not have diabetes. The trial involved more than 2,500 people in nine countries. The participant’s average weight was 105 kilograms (230 pounds) and they were asked to give themselves weekly injections of the drug at low (5 mg), medium (10 mg), and high (15 mg) doses or a placebo for 72 weeks. This trial was a double-blinded, randomized, multi-center, parallel, placebo-controlled trial. 

The most effective dosage of the drug was the highest, and on average this dosage helped reduce the body weight of the participants by 22.5 percent. 

"Tirzepatide is the first investigational medicine to deliver more than 20 percent weight loss on average in a phase 3 study, reinforcing our confidence in its potential to help people living with obesity," said Jeff Emmick, MD, PhD, vice president, product development, Lilly, in a statement. 

This drug can trigger many side effects like vomiting, diarrhea, nausea, and constipation, which get worse the higher the dose. However, one advantage of obesity drugs is that they can be stopped at any time, unlike some surgical options like bariatric surgery which change how you eat for the rest of your life. 

The company does need to conduct more monitoring to see if this drug is also useful for preventing type 2 diabetes. 

Caution should be held as this study was conducted by the pharmaceutical company themselves and has not been published yet – so it is not yet peer-reviewed. However, if all goes well, the drug may become available on the market in a few year’s time.