Recent analyses have highlighted three medications known as GLP-1 receptor antagonists, which have demonstrated significant weight loss compared to placebo treatments. However, researchers noted gaps in the available evidence, particularly regarding long-term health impacts, side effects, and potential conflicts of interest due to industry funding.
Transition from Diabetes Management to Weight Control
Initially created to treat type 2 diabetes, GLP-1 receptor agonists have been in clinical use since the mid-2000s. These drugs have proven effective in managing blood sugar levels and reducing the risk of heart and kidney complications in diabetic patients, especially those with existing heart or kidney issues. They also support weight loss and decrease the likelihood of premature mortality.
In recent years, there has been a growing interest in utilizing these medications for individuals struggling with obesity. These drugs mimic a natural hormone that slows digestion and enhances feelings of satiety. In the UK, they are approved for weight management in conjunction with a calorie-restricted diet and physical activity for those with obesity or weight-related health issues.
Weight Loss Outcomes with GLP-1 Medications
In various studies, tirzepatide (Mounjaro and Zepbound), semaglutide (Ozempic, Wegovy, and Rybelsus), and liraglutide (Victoza and Saxenda) have shown impressive weight loss results over periods of one to two years when compared to placebo treatments. The positive effects seem to persist as long as patients continue their treatment.
- Tirzepatide, administered weekly, resulted in an average weight loss of approximately 16% after 12 to 18 months. Data from eight randomized controlled trials involving 6,361 participants suggest this weight loss could be maintained for up to 3.5 years, although long-term safety data is still limited.
- Semaglutide, also injected weekly, led to an average weight reduction of about 11% after 24 to 68 weeks. Findings from 18 randomized controlled trials with 27,949 participants indicate that this effect can last for up to two years. Participants using semaglutide were more likely to experience at least a 5% reduction in body weight, although they reported higher instances of mild to moderate gastrointestinal side effects.
- Liraglutide, given as a daily injection, showed more modest outcomes, with an average weight loss of around 4-5% based on 24 trials involving 9,937 participants. Nevertheless, a greater number of individuals achieved significant weight loss compared to those on placebo, although evidence for effectiveness beyond two years is limited.
Regarding major cardiovascular events, quality of life, or mortality rates, researchers found minimal differences between the GLP-1 medications and placebo. Side effects, particularly nausea and digestive issues, were reported more frequently with these drugs, leading some participants to discontinue their use.
"These medications have the potential to facilitate substantial weight loss, especially within the first year," states Juan Franco, co-lead researcher from Heinrich Heine University Düsseldorf, Germany. "This is a thrilling development after many years of unsuccessful attempts to discover effective treatments for obesity."
Concerns Regarding Funding and Accessibility
A significant portion of the studies examined were funded by the pharmaceutical companies producing these drugs. In many instances, these companies were heavily involved in the design, execution, analysis, and reporting of the trials. Such involvement raises concerns about potential conflicts of interest and highlights the necessity for more independent research.
The authors emphasize that the broader application of GLP-1 medications must consider social and commercial health determinants, including cost, insurance coverage, and overall accessibility. Without careful consideration, increased usage could exacerbate existing health disparities among individuals facing obesity. Currently, the high prices of semaglutide and tirzepatide limit access, while liraglutide has become more affordable following the expiration of its patent, allowing generic alternatives to enter the market. Semaglutide's patent is also set to expire in 2026.
Most of the reviewed trials were conducted in middle- and high-income nations, with regions such as Africa, Central America, and Southeast Asia being underrepresented or entirely absent. Given the diverse body compositions, diets, and health behaviors across different populations, researchers stress the need for further studies on the effectiveness of these medications in varied global contexts.
"We require more information on the long-term effects and other cardiovascular health outcomes, especially in lower-risk individuals," remarks Eva Madrid, co-lead researcher from the Universidad de Valparaíso, Chile. "The potential for weight regain after treatment cessation may impact the long-term sustainability of the observed benefits. More independent studies from a public health perspective are essential."
Need for Long-Term Evidence to Shape Future Guidelines
The reviews underscore the importance of conducting longer-term, independently funded studies to inform both medical practices and public health policies. A clearer understanding of the sustained benefits and risks will be pivotal in defining the role of GLP-1 receptor agonists in long-term weight management.
These findings, commissioned by the World Health Organization, will contribute to the development of new WHO guidelines regarding the use of GLP-1 receptor agonists for obesity treatment.