Tirzepatide is a new drug that has been developed to treat type 2 diabetes, a condition where the body cannot use insulin properly to regulate blood sugar levels. However, tirzepatide also has an amazing and unexpected effect: it makes people lose a lot of weight, more than any other weight loss medication. In a recent clinical study, patients who took tirzepatide lost more than 20% of their body weight (52 pounds, or 23.6 kg), compared to 3.1% for placebo.
How does tirzepatide work?
Scientists are not sure, but they think they may have created a new synthetic hormone by combining the two natural hormones that tirzepatide copies.
The obesity problem
Obesity is a condition where fat cells store too much fat, which makes them work poorly. Fat cells are not just passive storage units; they also produce hormones that affect many aspects of metabolism, such as appetite, energy expenditure, inflammation, and blood sugar control. When fat cells store too much fat, they become dysfunctional and release molecules that can cause various health problems, such as diabetes, high blood pressure, heart disease, cancer, asthma, and high cholesterol. These health problems can reduce the quality and length of life for people with obesity. To prevent or reverse these problems, people with obesity need to lose at least 5% to 10% of their body weight. However, this is not easy to do with lifestyle changes (such as diet and exercise) alone. Some people may not respond well to these changes, or may find them hard to maintain. Some drugs can help, but they are not very effective or suitable for everyone. For example, orlistat, a drug that blocks fat absorption in the gut, only works in about half of the patients who take it.
Tirzepatide: a diabetes drug that leads to weight loss
Tirzepatide is a drug that acts like two hormones that are released by the gut after a meal: glycogen-like protein-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). These hormones help the body produce more insulin, which lowers blood sugar levels after eating. Tirzepatide was designed to treat type 2 diabetes by improving blood sugar control in patients who cannot use insulin properly. However, it also has a surprising side effect: it causes weight loss that surpasses the best weight loss drugs available today. In a recent clinical study, patients who took tirzepatide lost up to 21% of their body weight (an average of 52 pounds, or 23.6 kg), compared to 3.1% for placebo. This is surprising because one of the hormones that tirzepatide acts like, GIP, was thought to cause obesity.
Tirzepatide acts like a new synthetic hormone
Scientists do not fully understand how tirzepatide causes weight loss. One theory is that tirzepatide acts like a new synthetic hormone that has different effects than the natural hormones it copies. GLP-1 and GIP are normally released as separate molecules by different cells in the gut. They bind to their own receptors on different cells in the body. Tirzepatide is a single molecule that binds to both receptors at the same time. Moreover, tirzepatide has special features that make it last longer than the natural hormones in the bloodstream. These structural differences may make tirzepatide trigger different cellular processes than GLP-1 and GIP do separately.
GLP-1 is well known for its role in weight loss and diabetes management. It reduces appetite and food intake by acting on the brain and the stomach. It also stimulates insulin production by acting on the pancreas. Some popular weight loss medications (like semaglutide) and diabetes medications (like liraglutide) share structures with GLP-1 and stimulate the GLP-1 receptor.
GIP, on the other hand, is less understood. It does not affect appetite or food intake like GLP-1 does. Instead, it enhances insulin production by acting on the pancreas and other tissues. However, many studies suggest that GIP promotes obesity by increasing fat storage and preventing fat breakdown in fat cells and other tissues. For example, humans who have genetic defects in the GIP receptor are more likely to have lean body mass than those who have normal GIP receptors. Therefore, scientists generally believed that blocking the GIP receptor would induce weight loss; however, tirzepatide stimulates the GIP receptor.
Tirzepatide is still being reviewed by the FDA, but it has the potential to be a game-changer in the fight against obesity and diabetes. It is the first drug that mimics both GLP-1 and GIP, and it may act like a new synthetic hormone that has unique effects on the body. The drug maker Eli Lilly plans to apply for approval in April 2023.
