The introduction of GLP-1 drugs has turned the weight loss industry into big business. But what are these drugs, how effective are they, and what are the likely side effects?
The size of the GLP-1 drugs market is enormous. In 2024, it was calculated to be $49.9 billion, estimated to reach an eye-watering $879.9 billion by 2034. Women rather than men seem to be the biggest users of these drug,s and a recent survey of over 1,000 women found that nearly three-quarters (72%) said that they would consider using them to help lose weight.
How GLP-1 drugs work
Before looking at how these GLP-1 drugs work, it’s important to understand how our bodies control blood glucose (or sugar) levels. The amount of glucose in the blood is kept relatively constant for good reasons. If levels fall too low or go too high, it can be disastrous, leading to several complications and even death.
Blood glucose levels are kept within a narrow range through the actions of two hormones produced by the pancreas: insulin and glucagon, which have opposing effects. After eating foods high in sugar, insulin helps lower the surge in blood glucose levels, shifting it into the liver and muscles for storage. When levels fall, glucagon stimulates the release of glucose from these liver stores, increasing levels back to normal.
In the 1980s, scientists discovered another way of controlling blood glucose levels. A third hormone, known as glucagon-like peptide-1 (GLP-1), is produced in the gut in response to eating. Following a meal, GLP-1 causes the release of insulin and halts the production of glucagon. In fact, it was shown that injecting GLP-1 into healthy people given a meal containing glucose caused insulin levels to rise and glucose levels to fall. GLP-1 does its job by attaching to a specific GLP-1 receptor on cells. However, because GLP-1 is quickly broken down by the body, it was very difficult to manufacture.
Across many years, this led to the development of several drugs which mimicked the action of GLP-1. Several are currently available, including liraglutide and semaglutide, the latter of which is best known by its brand names Ozempic or Wegovy. Scientists realised that these GLP-1 drugs could be used to treat type 2 diabetes, in which the body doesn’t produce enough insulin, leading to high blood glucose levels. But how do these drugs help with weight loss?
GLP-1 drugs and weight loss
The idea that GLP-1 drugs could be used as a treatment for weight loss arose from an observation in the trials of people with type 2 diabetes. Not only did individuals see an improvement in their diabetes control, but they also lost weight. The reason for this weight loss is that a second effect of GLP-1 drugs is to slow digestion by delaying stomach emptying. As food remains in the stomach for longer, it helps people feel fuller for longer. As a result, they eat less and ultimately lose weight. However, it’s worth noting that delayed digestion can also lead to nausea or vomiting, which is the most common side effect of GLP-1 drugs.
The discovery that GLP-1 drugs are suitable for weight loss came from a 2015 trial with liraglutide, which showed an average weight loss of 8.4 kg among those who dieted and increased their exercise. Other trials with different GLP-1 drugs have solidified these findings.
But it turns out that as well as GLP-1, there is a second gut hormone with a similar effect. This hormone is known as glucose-dependent insulinotropic polypeptide (GIP). Although semaglutide only works at the GLP-1 receptor, the newer drug, tirzepatide (Mounjaro) works at both receptors. This dual effect suggests that Mounjaro would work better, with studies finding that the drug is indeed more effective for weight loss. People can lose life-changing quantities of weight, with a recent analysis of overweight and obese patients finding that 12-month use of Mounjaro led to an average weight loss of 17.2 kg or 16.5% of their body weight.
Tirzepatide safety
Any drug can have side effects which patients in clinical trials identify. All of these side effects must be listed by the manufacturer in the summary of product characteristics, which is a technical bible for the drug, and listed under undesirable effects. The incidence of these side effects is categorised as ‘very common’, ‘common’, ‘uncommon’ and ‘rare’. For example, a side effect categorised as ‘very common’, such as nausea, is likely to occur in more than 1 in 10 or 10% of people taking the drug. But clinical trials only include a relatively small number of people. Once a drug is used by thousands or even millions of people, as is the case with Ozempic and Mounjaro, there is the possibility that unexpected side effects, i.e., those not already known to the manufacturer, are likely to appear.
While Mounjaro has a number of recognised side-effects like nausea and other gastrointestinal (GI) issues, several unexpected effects are starting to emerge.
Unexpected side-effects of Mounjaro
Following approval of a drug, the manufacturer conducts post-marketing surveillance. This provides a way to identify the real experiences of people using the drug outside a clinical trial. It’s also a way of recognising any unexpected side effects. One formal analysis has already identified the following previously unknown side effects.
- Palpitations, chest discomfort and generalised muscle aches
- Neck and back pain, as well as morning headaches
There have also been a small number of cases of patients taking Mounjaro who experience suicidal thoughts. Trying to link these unexpected effects to Mounjaro and not to something else is not always easy. That’s not to say these effects should be ignored; if more cases are seen over time, then it might be possible to make a connection with the drug. It’s also worth noting that, in the age of social media, people can report all sorts of symptoms they experience after starting Mounjaro (albeit not through official channels). In fact, in a recent trawl through social media posts, the following unexpected side effects were reported.
- Vivid dreams with heightened clarity
- Tingling and strange sensations, such as pins and needles
- Changes to body odour or increased sweating
- Taste disturbances
- Itchy or dry skin
- Emotional numbness/shakiness, internal jitters
Fortunately, many of these appeared to be mild and short-lived. Nevertheless, if you experience anything unusual while using Mounjaro, be sure to let your health professional at The Virtual Slimming Clinic know. It might be nothing, but it’s essential to keep a close eye on any unexpected side effects as Mounjaro use becomes more widespread.
Visit us for more
If you’re interested in getting your own prescription for Mounjaro or another weight loss treatment, make sure to visit us at The Virtual Slimming Clinic today. We also have a range of guides and blogs available to read from our website, so you can feel informed before you make any medical decisions. Give us a visit or get in touch for more guidance on your weight loss journey.
