Tirzepatide — the active ingredient in Mounjaro and Zepbound — was designed as a blood-sugar drug. But across a sequence of large randomised trials, it and its GLP-1 cousins have kept producing benefits that nobody set out to find: cardiovascular protection, kidney preservation, cartilage regeneration, liver recovery, and reduced alcohol cravings. None of those were on the original label.
This article reviews the evidence for GLP-1 and GLP-1/GIP medications beyond weight loss, compares tirzepatide with pure GLP-1 drugs and the emerging triple agonist retatrutide, and covers the micronutrient implications of lower calorie intake on these medications.
Table of Contents
- The Drug That Kept Becoming Something Else
- The Joint Surprise
- Liver and Alcohol
- Why Tirzepatide and Not Pure GLP-1
- The Evidence Case for Low-Dose Use
- Why Not Retatrutide
- Clinical Experience: Low-Dose Tirzepatide
- Safety Concerns
- Micronutrients on GLP-1 Medications
- References
The Drug That Kept Becoming Something Else
When John Eng found GLP-1 in the saliva of the Gila monster in the early 1990s, all it was supposed to do was lower blood sugar. He was an endocrinologist at the Bronx VA, working on lizard venoms in his spare time. The peptide he isolated acts on the same receptor as human GLP-1, but lasts much longer in the body. It became Byetta — the first GLP-1 drug approved, in 2005 [4].
But in the early diabetes trials, not only did patients lower their blood sugar levels, which was expected, but they also started losing weight. And not just a little bit of weight. Enough that doctors started noticing. By the mid-2010s, the SCALE trial had confirmed that liraglutide, which is another GLP-1 medication, caused significant weight loss [5].
By 2021, the STEP program tested semaglutide at a higher 2.4mg dose for obesity, and it resulted in around 15% body-weight loss. The GLP-1 medications had graduated from just a blood-sugar drug to a weight-loss drug [6].
And the field assumed — reasonably — that every benefit from here on out would just be downstream of the weight coming off.
But that's not what the trials found.
Surprise number two. November 2023. The SELECT trial. More than 17,000 adults with overweight or obesity and established heart disease — but no diabetes — randomised to weekly semaglutide or placebo. After a little more than three years, semaglutide cut major cardiovascular events by 20% [1].
Twenty percent. In people without diabetes. And when the trialists ran the numbers separately for people who lost a lot of weight versus very little, a chunk of the cardiovascular benefit didn't track with how much weight came off. This is important. GLP-1 medications appeared to offer cardiovascular benefits beyond the weight-loss effect.
Surprise number three. May 2024. The FLOW trial. About 3,500 adults with type-2 diabetes and chronic kidney disease — semaglutide versus placebo. The primary kidney composite — a combination of kidney failure rates, large eGFR drops, kidney or cardiovascular death — dropped by 24% [2].
And the authors said something specific. The effect on kidney health was unrelated to changes in body weight.
Again, weight loss wasn't the whole story. GLP-1 medications were offering other additional benefits.
There's also new evidence that GLP-1 meds are associated with a reduction in cancer progression. Real-world data presented at ASCO 2026 suggests GLP-1 receptor agonists may reduce metastatic progression of certain obesity-related cancers — lung, breast, colorectal, and liver [7].
The Joint Surprise
Surprise number four, and this one is remarkable.
Cartilage has no blood supply. No nerves. No efficient way to deliver the cells and nutrients needed to grow new tissue. It's one of the few structures in the human body that, once damaged, is severely limited in its ability to repair itself [8].
But then patients on Ozempic started saying something that their doctors initially dismissed. Their joints felt better. Not just less pain from carrying less weight. Something else. Something unexpected.
The obvious explanation was weight loss. Less weight means less mechanical pressure on joints. Every kilogram lost takes roughly four kilograms of stress off the knees [9].
So when Ozempic patients reported less joint pain, doctors shrugged: of course your knees hurt less — you lost 30 pounds.
The STEP 9 trial, published in the New England Journal of Medicine in 2024, seemed to confirm this. 407 patients with obesity and knee osteoarthritis. After 68 weeks, pain scores dropped 42 points with semaglutide compared to 28 with placebo. But patients also lost 13.7% of their body weight [10].
Case closed. Or so everyone thought.
But a team of researchers at the Shenzhen Institutes of Advanced Technology — part of the Chinese Academy of Sciences — weren't satisfied with that explanation. Led by Di Chen, they designed an experiment that would test it directly.
This is the study that changes the conversation. Chen's team took mice with osteoarthritis and split them into groups. One group received semaglutide. Another group was pair-fed — meaning they were given restricted calories, carefully controlled so they lost the exact same amount of weight as the semaglutide group. Same weight loss. No drug [11].
If the joint improvements were "just the weight loss," both groups should look the same.
They didn't. The pair-fed mice lost the same weight. But their cartilage kept deteriorating. Only the semaglutide group showed preserved cartilage, reduced inflammation, and fewer bone spurs. Same weight loss — completely different outcomes in the joints.
Di Chen explained the implications: this controlled experiment demonstrates that semaglutide's protective effect on cartilage in osteoarthritis is independent of weight loss, challenging the traditional belief that osteoarthritis improvement relies solely on weight reduction [12].
So if it's not weight loss, what's happening?
Here is the simplest way to think about it. Cartilage cells — called chondrocytes — need energy to maintain and repair the tissue around them. In osteoarthritis, those cells get stuck running on an inefficient fuel source. Think of it like a factory running on a sputtering generator. Barely enough energy to keep the lights on. Not nearly enough to rebuild anything.
What semaglutide does is flip a switch inside those cells that upgrades them to a clean, efficient energy source that produces dramatically more energy — enough to actually start repairing. Technically, GLP-1 receptors — which nobody expected to find on cartilage cells — activate the AMPK-PFKFB3 signalling cascade, shifting the cells from glycolysis to oxidative phosphorylation [11].
But mouse cartilage isn't human cartilage. Does it actually work in people?
Chen's team ran a pilot clinical study. 20 patients aged 50 to 75, all with obesity and knee osteoarthritis. Half received standard treatment — hyaluronic acid injections. The other half received hyaluronic acid plus weekly semaglutide.
After 24 weeks, they underwent MRI scanning. The semaglutide group showed an average 17% increase in cartilage thickness, suggesting regeneration. The control group: less than 1%. The thickened cartilage was visible in weight-bearing areas of the knee — the areas that take the most punishment [11].
Patients also experienced reduced pain and improved joint function.
Liver and Alcohol
GLP-1 medications also show benefits for liver disease and alcohol use disorder.
The ESSENCE trial of semaglutide for biopsy-defined MASH (the more severe form of fatty liver disease) found that resolution of steatohepatitis without worsening of fibrosis occurred in 62.9% of the semaglutide group versus 34.3% of the placebo group [13].
And in 2026, The Lancet published a randomised, double-blind, placebo-controlled trial of once-weekly semaglutide in patients with alcohol use disorder and comorbid obesity. Semaglutide was associated with a reduction in heavy drinking days compared with placebo [14].
Two more organ systems. Two more results in tissues nobody set out to study.
Why Tirzepatide and Not Pure GLP-1
The evidence reviewed so far covers GLP-1 medications broadly. But tirzepatide has a second mechanism: it combines GLP-1 with GIP (glucose-dependent insulinotropic polypeptide). Tirzepatide is sold under the brand names Mounjaro (for type-2 diabetes) and Zepbound (for obesity).
The trial that compares these drug classes head-to-head for the first time is SURPASS-CVOT, published in two stages — the primary outcome in NEJM in December 2025, and a follow-up cardiorenal analysis in JAMA Cardiology in March 2026. Tirzepatide — the dual GLP-1 plus GIP drug — versus dulaglutide, which is pure GLP-1. Thirteen thousand patients with type-2 diabetes and established heart disease, followed just over four years [3].
Here is the part the headlines didn't put first. The primary endpoint was the classic three-point MACE — cardiovascular death, heart attack, or stroke. Tirzepatide did not beat dulaglutide on that endpoint. It cleared the "no worse than" bar cleanly. But on the harder question — "is it actually better?" — the result came in just short of the threshold the researchers had committed to before the study started. By their own rules, going in, that counts as a miss.
Now here is the part that made the conversation. The same investigators ran an after-the-fact — "post-hoc" — analysis in JAMA Cardiology 2026. They widened the endpoint to six components — adding heart-failure hospitalisation, coronary revascularisation, all-cause death, and a renal composite to the original three. On that wider endpoint, tirzepatide reduced risk by 16% relative to dulaglutide.
Overall, the evidence supports GLP-1 and GLP-1/GIP medications producing benefits beyond weight loss itself.
The Evidence Case for Low-Dose Use
The large trials enrolling lean, non-diabetic adults have not yet been run. Every major study — SELECT, FLOW, SURPASS-CVOT — enrolled people with diabetes, obesity, kidney disease, or established cardiovascular disease.
The narrower argument for low-dose use in otherwise healthy individuals rests on the finding that these drugs appear to produce biological effects that are partly independent of weight loss itself. Across several organ systems and trial populations, the weight-loss hypothesis kept failing to explain the full benefit. That is a consistent signal, even if its applicability to low-risk individuals remains untested.
Dr Michael Albert — a US internist — wrote about taking low-dose tirzepatide for two years in March 2026, framed explicitly as a personal choice, not a recommendation [15].
His piece is worth reading in full for a first-person account of the considerations involved.
Why Not Retatrutide
Retatrutide is a triple agonist with a third component that acts on glucagon receptors. Glucagon agonism increases metabolic rate. For an obesity drug at the population level, that's a feature. For lean individuals trying to maintain muscle mass, pushing energy expenditure up is the wrong direction.
With that rise in metabolic rate comes a dose-dependent rise in resting heart rate — three to seven beats per minute in a phase 2 trial [16].
Tirzepatide also raises heart rate, typically two to four beats per minute. That signal is seen across GLP-1-based drugs, but appears more pronounced with retatrutide's added glucagon activity [17].
The phase-3 retatrutide cardiovascular data is still pending. For individuals without a metabolic reason to increase energy expenditure, the risk-benefit calculus for retatrutide is currently less clear than for tirzepatide.
Clinical Experience: Low-Dose Tirzepatide
Physicians who have publicly reported using low-dose tirzepatide — including Dr Michael Albert [15] and Dr Brad Stanfield (who discloses owning MicroVitamin) — describe a consistent pattern. At 1.25mg per week, the most commonly reported benefit is a marked reduction in "food noise" — the persistent cognitive background of hunger and cravings — making it substantially easier to maintain a nutrient-dense diet. Reported cardiovascular effects include reductions in blood pressure, in some cases allowing medication dose reduction.
Initial side effects — nausea, fatigue — are common on starting but typically diminish with each successive injection, often resolving entirely within weeks.
Preserving muscle mass requires active effort. Resistance training and adequate protein intake are recommended alongside any GLP-1 regimen to counter the loss of lean mass that can accompany calorie reduction.
Safety Concerns
Three safety signals have received particular scrutiny in the literature.
Pancreatitis: Early concerns were raised, but real-world data have not confirmed an increased risk — no clear evidence of increased pancreatitis risk has been observed in large pharmacovigilance analyses [18].
Thyroid cancer: Rodent studies raised a theoretical concern. In real-world follow-up of semaglutide-treated patients, the incidence of thyroid cancer was less than 1%, suggesting no significant risk at the population level [19].
Suicidality: The FDA and EMA — the European drug regulator — both reviewed this signal in 2024 and found no causal link. Their preliminary evaluation does not suggest a causal association [20].
Micronutrients on GLP-1 Medications
A practical consequence of GLP-1 medication use is reduced calorie intake. On a GLP-1, daily calorie intake typically drops by 16 to 39% [21]. Weight loss of several kilograms over months is common even at low doses.
The American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society have published a joint advisory on nutritional considerations for GLP-1 users. They suggest considering a multivitamin-mineral supplement — not as a requirement and not as a guarantee against deficiency, but as a practical baseline [22]. Nutrients flagged as being at particular risk of inadequacy include iron, calcium, magnesium, zinc, and vitamins A, D, E, K, B1, B12, and C.
From the MicroVitamin range
MicroVitamin is a 25-ingredient daily multivitamin that includes the key micronutrients flagged in the joint GLP-1 advisory — vitamin D, B12, magnesium, zinc, and others — and has been independently tested by Labdoor, scoring 99.7% [23]. MicroVitamin.
It is worth noting that the joint advisory does not say supplementation is required, nor that it corrects deficiencies in full. It reflects the practical reality that eating significantly less food over months makes it harder to meet micronutrient needs from diet alone, and that a broad-spectrum supplement can help close that gap while the research on optimal GLP-1 nutritional protocols continues to develop.
References
1. https://www.nejm.org/doi/full/10.1056/NEJMoa2307563
2. https://www.nejm.org/doi/10.1056/NEJMoa2403347
3. https://www.nejm.org/doi/abs/10.1056/NEJMoa2505928
4. https://en.wikipedia.org/wiki/Exenatide
5. https://www.nejm.org/doi/full/10.1056/NEJMoa1411892
6. https://www.nejm.org/doi/full/10.1056/NEJMoa2032183
8. https://pmc.ncbi.nlm.nih.gov/articles/PMC10071204/
9. https://pubmed.ncbi.nlm.nih.gov/15986358/
10. https://www.nejm.org/doi/abs/10.1056/NEJMoa2403664
11. https://www.cell.com/cell-metabolism/fulltext/S1550-4131(26)00008-2
13. https://www.nejm.org/doi/full/10.1056/NEJMoa2413258
14. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(26)00305-3
16. https://www.nejm.org/doi/full/10.1056/NEJMoa2301972
17. https://www.nejm.org/doi/full/10.1056/NEJMoa2107519
18. https://pubmed.ncbi.nlm.nih.gov/32720500/
19. https://pmc.ncbi.nlm.nih.gov/articles/PMC11050669/
21. https://pmc.ncbi.nlm.nih.gov/articles/PMC11340591/
22. https://pmc.ncbi.nlm.nih.gov/articles/PMC12304835/
23. https://labdoor.com/review/dr-brad-stanfield-microvitamin
