There has been nothing short of a seismic shift in the weight loss space since new weight management medications such as Mounjaro came on the scene.
You would have had to have been seriously not paying attention not to know this.
The drugs have dramatically altered the options for people living with obesity, and the success of the drugs has meant that people who don’t meet the NHS criteria for prescription have been clamouring for them.
Pause for a serious health message here – if you’re looking to buy any of these drugs privately, it’s vital to do this through a medical doctor or a reputable company that employs prescribing doctors, and not via unregulated sites on the internet. The health risks are way too serious.
How do they work?
No-one fully understands the mechanisms behind these weight management medications (WMMs). Listening to people who are taking the drugs, you hear of a dramatic change in their inner landscape around food, eating and appetite. Fullness feels different or comes sooner, they have reduced interest in food and a dramatic reduction in ‘food noise’ – a continual mental chatter involving food and eating.
We might not know the mechanism, but it is clear that the drug is affecting physical sensations associated with appetite, and mental processes involved in thinking about, finding and consuming food.
What sort of drugs are they?
As relatively new kids on the block, these medicines are a source of curiosity and intrigue. Are they a bit like other drugs we are more familiar with?
- Are they for example a bit like an antibiotic? If so, a course of treatment would correct the biological problem (bacterial infection in the case of the antibiotic; faulty appetite signalling in the case of WMMs) and when you got to the end of the course, you would be better and could discontinue it with the beneficial changes intact.
- Or maybe more like drugs for hypertension? Here, the drug corrects the underlying biological mechanisms (regulating blood pressure) whilst you are taking it, but if you discontinue it, the mechanisms governing your blood pressure revert to their harmful patterns. These drugs need to be taken over the long term to maintain healthy blood pressure.
- Or perhaps are they more like anti-depressants? Some people can take anti-depressants for a limited period, during which time the lift in mood and energy allows them to make changes – perhaps through psychological therapy – which then persist as the drug is tapered off.
Weight management medications are of course none of the above, but this might be a useful analogy for how they work.
Outcomes
One indicator of how WMMs work is outcome studies on people who take, and then stop taking the medication. A recent systematic review* showed that while WMMs are undeniably effective in achieving initial weight loss, the data clearly indicate that their benefits are vulnerable to reversal once treatment is ceased.
The authors of this study say this, “provides robust quantitative evidence that weight regain is not a treatment failure but a predictable biological response and must be anticipated and addressed in clinical practice. By reframing pharmacotherapy as a maintenance tool rather than a finite intervention, healthcare systems can better support patients in achieving sustained, long-term weight control and improved metabolic health.”
This study puts the medication firmly in the blood pressure medication category.
Another systematic review and meta-analysis of the literature** concluded that
- Real world observations estimate that around 50% of people with obesity discontinue WMMs within 12 months
- People on average regain weight at a rate of 0.4 kg/month after cessation of WMMs, leading to a projected return to baseline weight after 1.7 years
Again, a bit like blood pressure medication.
This opens a whole other question, of what would be helpful for the 50% of people who stop the medication within a year. Following the massive success of these medications for many people, this is becoming the million dollar “what-else-is-needed?” question.
Too early to tell
It is early days, and there’s so much to learn.
My own hunch, for what it’s worth, is that if you take WMM that significantly alters your appetite signalling while you’re taking it, you can only partly establish behavioural changes to how you’ll eat when you stop the medicine. I say that because as your appetite signals revert to how they are without the medication, you’ll feel less full, or more hungry, or the food noise may return.
In other words, the pressures on you to eat will be different. So I’m on the fence straddling hypertension and anti-depressant type descriptions.
Of course it’s possible that WMMs may affect different people differently so that some people react as though it’s like an anti-hypertensive and some like an anti-depressant, and maybe even some who respond more like an antibiotic.
We are living in interesting times, and need to keep listening, reading and learning.
References
* Kolli RT et al (2025) Rebound or Retention: A Meta-Analysis of Weight Regain After the Discontinuation of Glucagon-Like Peptide-1 (GLP-1) Receptor Agonists and Other Anti-obesity Drugs. Cureus. 2025 Oct 19;17(10):e94926. doi: 10.7759/cureus.94926. PMID: 41116804; PMCID: PMC12535773.
** Weight regain after cessation of medication for weight management: systematic review and meta-analysis. BMJ 2026; 392 doi: https://doi.org/10.1136/bmj-2025-085304 (Published 07 January 2026)
Photo courtesy of World Obesity Federation