Nearly 40% of American adults are obese and 70% of those aged 20 and over are overweight, putting them at considerable risk of developing cancer and cardiovascular disease. It’s a huge public health issue that has long since reached epidemic proportions.

Dieting and exercise are some tried and proven ways to lose weight, but research suggests that it is exceedingly difficult. One 2020 meta-analysis looked at the results of 121 weight loss trials that enrolled nearly 22,000 overweight or obese adults who followed one of 14 popular diets, including the Atkins diet, Weight Watchers, Jenny Craig, DASH, and the Mediterranean diet.

The researchers found that while low-carb and low-fat diets both resulted in weight loss of about 10 pounds over a period of six months, most of the lost weight was regained within one year.

The lesson here is not that dieting doesn’t work (it does), but rather that sticking to a particular diet is hard so in a given cohort of obese patients, most will relapse if they are not offered additional support.

But this is where a number of new weight loss drugs might come in.

You might have heard about Ozempic and Wegovy, two injectable drugs that are making the rounds on TikTok, with people sharing their incredible weight loss journeys.

But another very similar drug, known as tirzepatide and manufactured by big pharma giant Eli Lilly and Co., may be even more powerful.

The company just wrapped up its second phase 3 clinical trial, which provided amazing results, boasting up to 16% body weight reduction, or more than 15 kilograms (34 pounds), over nearly one and a half years. Patients who received a placebo experienced a 3.3% average reduction in body weight.

These remarkable effects will probably see the drug fast-tracked for FDA approval for weight loss purposes, although tirzepatide is already FDA-approved for diabetes, the condition it was originally designed to address. Lily plans on selling tirzepatide for weight loss under the brand name Mounjaro.

The first phase 3 clinical trial, which also saw the drug tested on non-diabetic obese and overweight patients using various doses, had even better results. Patients lost 24 kilograms (52 pounds) on average when using the highest dose of tirzepatide.

“If everybody who had obesity in this country lost 20% of their body weight, we would be taking patients off all of these medications for reflux, for diabetes, for hypertension,” Dr. Caroline Apovian, a director of the Center for Weight Management and Wellness at Brigham and Women’s Hospital, told AP. “We would not be sending patients for stent replacement.”

How tirzepatide works

When the body needs calories, the gut releases the hormone ghrelin which makes us feel hungry. After eating a meal, the body produces less of the hunger hormone, while fat tissues and the stomach release hormones like PYY, GLP-1, and leptin to make us feel satiated. This dynamic interplay of chemical messages coordinates our eating behavior and food choices.

However, when we experience weight loss due to being on a calorie deficit, the body produces more hunger hormones and less satiety hormones, leading to persistent feelings of hunger, reduced feelings of fullness, and slower burning of calories. Our body doesn’t want us to lose weight, so it’s making our lives miserable as a result.

Drugs like Ozempic and Wegovy mimic GLP-1, boosting the release of insulin and slowing the release of sugar from the liver. Tirzepatide does this, but in addition, it also mimics the effects of GIP, another hormone released by the human gut when we’re full after a meal.

Armed with these new results, Lilly registered a new phase 3 trial last week in which it plans to test tirzepatide directly against Wegovy, also known as semaglutide.

Weglovy and its other similar rival drug Ozempic from Novo Nordisk were approved for weight loss in 2021. In the following year, both drugs grossed sales totaling nearly $10 billion. However, industry analysts project sales topping $50 billion annually for tirzepatide, thanks to its much better results.

These sales projections might sound shocking, but they make sense once you consider the sheer number of potential patients numbering in the tens of millions, but also the price of these treatments. No word yet on the pricing of Mounjaro, but if it costs the same as the diabetes version, expect something in the range of $1,000 per month. Rival Wegovy is priced at $1,300 per month. These expenses are not covered by Medicare, while private insurance might cover only a fraction of the costs, depending on your plan.

And while the results of these drugs can be seen as nothing short of amazing, there is no such thing as a miracle drug. Clinical trials so far for both types of weight loss drugs suggest they are safe, but can cause side effects diarrhea, nausea, vomiting, constipation and stomach pain. Some patients have developed pancreatitis (inflammation of the pancreas), while others have developed gallbladder problems. It is also unclear what are the long-term effects of such medication since it is so new.