Oxyntomodulin: The Natural Dual Agonist That Suppresses Appetite
Satiety Peptides
19.3% reduction
Oxyntomodulin infusion reduced buffet meal energy intake by 19.3% in healthy volunteers, while also suppressing ghrelin by 44%.
Cohen et al., Journal of Clinical Endocrinology & Metabolism, 2003
Cohen et al., Journal of Clinical Endocrinology & Metabolism, 2003
View as imageYour gut releases a peptide after every meal that hits two different receptors at once, cutting your appetite through one and ramping up calorie burning through the other. That peptide is oxyntomodulin, and it has become one of the most studied natural dual agonists in metabolic research. As a satiety peptide released from the same intestinal L-cells that produce GLP-1, oxyntomodulin sits at the intersection of appetite regulation and energy balance. Its dual receptor profile has inspired an entire class of synthetic drugs now in clinical trials for obesity and type 2 diabetes.
Key Takeaways
- Oxyntomodulin reduced buffet meal intake by 19.3% and suppressed the hunger hormone ghrelin by 44% in a human infusion study (Cohen et al., 2003)
- The appetite-suppressing effect works through the GLP-1 receptor, while the energy expenditure increase requires the glucagon receptor (Scott et al., 2018; Baggio et al., 2004)
- Four weeks of subcutaneous oxyntomodulin injections produced 2.3 kg of weight loss versus 0.5 kg with placebo in overweight subjects (Wynne et al., 2005)
- Native oxyntomodulin increased insulin secretion and improved glucose tolerance comparably to liraglutide in obese patients with type 2 diabetes (Shankar et al., 2018)
- A triple-hormone combination of GLP-1, oxyntomodulin, and PYY produced 4.4 kg weight loss over 4 weeks with superior glucose control compared to gastric bypass surgery (Behary et al., 2019)
- Oxyntomodulin's short half-life of 2-8 minutes has driven the development of long-acting synthetic analogs like mazdutide and survodutide (Zhihong et al., 2023)
What Is Oxyntomodulin?
Oxyntomodulin (OXM) is a 37-amino acid peptide produced by cleaving the proglucagon gene in intestinal L-cells. The same gene produces glucagon in the pancreas and GLP-1 in the gut, but tissue-specific processing enzymes determine which peptide gets made where.[1] OXM contains the full 29-amino acid glucagon sequence plus an 8-amino acid C-terminal extension called intervening peptide-1 (IP-1).
L-cells release OXM into the bloodstream after eating, alongside GLP-1 and peptide YY (PYY). Plasma OXM levels rise within 30 minutes of a meal and correlate with calorie content.[3] The peptide has a plasma half-life of only 2-8 minutes because dipeptidyl peptidase-4 (DPP-4) and other enzymes rapidly break it down. This short duration of action is why native OXM never became a drug on its own, but its dual receptor profile became the blueprint for a new generation of obesity treatments.
How Oxyntomodulin Suppresses Appetite
OXM reduces food intake through the GLP-1 receptor (GLP-1R). Baggio and colleagues at the University of Toronto demonstrated this in 2004 using knockout mice: OXM's anorectic effects were completely preserved in mice lacking the glucagon receptor but abolished in mice lacking the GLP-1 receptor.[1] Central injection of OXM inhibited food intake in wild-type mice, confirming that the appetite signal operates through brain GLP-1R pathways.
In the same study, OXM activated neuronal c-fos expression in the paraventricular nucleus of the hypothalamus, the area postrema, and the nucleus of the solitary tract, three brain regions that integrate satiety signals.[1] The exendin-4 (a potent GLP-1R agonist) comparison is telling: exendin-4 produced a more potent and sustained suppression of food intake than OXM at equivalent GLP-1R activation, which makes sense because OXM binds the GLP-1R with roughly 10-50 times weaker affinity than native GLP-1 itself.
The human data aligns with these preclinical findings. Intravenous OXM infusion at 3.0 pmol/kg/min reduced ad libitum buffet meal intake by 19.3% and cumulative 12-hour energy intake by 11.3% in 13 healthy volunteers (Cohen et al., 2003). OXM also suppressed preprandial ghrelin, the primary hunger-stimulating hormone, by 44% of the postprandial decrease. This ghrelin suppression may amplify the direct appetite-reducing effects.
How Oxyntomodulin Increases Energy Expenditure
The other half of OXM's metabolic equation, increased calorie burning, operates through the glucagon receptor (GCGR). Scott and colleagues developed a sustained-release OXM analogue called OX-SR and tested which receptor drove the thermogenic effect.[5] Blocking the GLP-1R with exendin 9-39 did not prevent OX-SR from increasing oxygen consumption in rats. But when glucagon receptor activity was eliminated, the energy expenditure boost disappeared entirely.
This division of labor, appetite suppression through GLP-1R and energy expenditure through GCGR, is what makes OXM unique among gut hormones. Most satiety peptides, including CCK, PYY, and pancreatic polypeptide, reduce food intake but do not independently increase energy expenditure.
Bagger and colleagues tested this directly in 15 healthy young men by infusing OXM, glucagon, GLP-1, and a glucagon+GLP-1 combination.[4] All four infusions reduced food intake by a similar magnitude compared to saline (roughly 15-17% reduction), but the mechanisms differed. OXM, GLP-1, and the GLP-1+glucagon combination slowed gastric emptying and reduced composite appetite scores, while glucagon alone did not affect either measure but still reduced food intake through a separate pathway.
The Glucagon Receptor Paradox
Activating the glucagon receptor raises blood sugar. Glucagon is the hormone your pancreas releases during fasting to mobilize glucose from the liver. So why would a peptide that activates the glucagon receptor be useful for metabolic disease?
The answer lies in OXM's dual activation. Kosinski and colleagues at Merck Research Laboratories created an OXM variant called OXMQ3E, identical to OXM except for a single amino acid change (glutamine to glutamic acid at position 3) that eliminated glucagon receptor activity while preserving full GLP-1R agonism.[2] In obese mice treated chronically, native OXM produced greater weight loss and better lipid-lowering than OXMQ3E, even though both had comparable blood sugar control. Co-administration of OXM with a glucagon receptor antagonist confirmed that the superior weight loss required activation of both receptors.
Shankar and colleagues took this question to human subjects. In a randomized, placebo-controlled crossover trial, they infused native OXM into 12 overweight/obese subjects without diabetes and 12 obese subjects with type 2 diabetes.[6] OXM at 3.0 pmol/kg/min increased insulin secretion rates and blunted glycemic excursion during a graded glucose infusion. In the type 2 diabetes group, OXM's effects on glucose-dependent insulin secretion were comparable to liraglutide. The GLP-1R activation counteracted any glucagon-driven glucose elevation, confirming that the dual mechanism can improve rather than worsen blood sugar control.
Weight Loss Evidence in Humans
The earliest weight loss trial of OXM in humans ran for 4 weeks (Wynne et al., 2005). Overweight and obese subjects received subcutaneous OXM injections three times daily before meals. The treatment group lost 2.3 kg over the study period compared to 0.5 kg in the placebo group, translating to an additional 0.45 kg of weight loss per week. Energy intake dropped by 25-35% at study meals.
A separate randomized controlled trial (Wynne et al., 2006) measured energy expenditure directly: OXM increased resting energy expenditure by approximately 26% above baseline, confirming the dual mechanism operates in humans as it does in rodent models. This combination of reduced intake and increased expenditure creates a larger calorie deficit than either mechanism alone would produce.
These results were modest by the standards of modern GLP-1 drugs, which reflects OXM's short half-life rather than its mechanistic potential. Each OXM injection worked for minutes, not hours. The principle it demonstrated, that targeting both receptors simultaneously produces better metabolic outcomes than targeting either one alone, became the foundation for a generation of synthetic dual agonists.
OXM in the Triple Hormone Combination (GOP)
Roux-en-Y gastric bypass (RYGB) surgery dramatically increases postprandial secretion of GLP-1, OXM, and PYY. Behary, Tan, and colleagues at Imperial College London hypothesized that infusing all three hormones together (the "GOP" infusion) could replicate the hormonal changes of bariatric surgery without the scalpel.[7]
In a randomized, single-blinded study, 15 obese patients with prediabetes or type 2 diabetes received subcutaneous GOP infusion for 4 weeks while 11 received saline. The GOP group lost 4.4 kg (95% CI: -5.3 to -3.5 kg) compared to 2.5 kg (-4.1 to -0.9 kg) with saline. The weight loss was smaller than RYGB achieved, but GOP produced superior glucose tolerance and reduced glycemic variability compared to both RYGB and very low-calorie diet. Fructosamine dropped by 44.1 umol/L in the GOP group versus 11.7 umol/L with saline (P = 0.0026).
This study highlights how gut satiety peptides work together to regulate appetite and metabolism. OXM's role in the combination provides the glucagon receptor activation that PYY and GLP-1 alone cannot.
OXM After Bariatric Surgery
Nielsen and colleagues measured postprandial OXM, glicentin, GLP-1, PYY, and ghrelin responses in 42 subjects before and 6 months after RYGB or sleeve gastrectomy (SG).[8] Postprandial OXM concentrations differed between RYGB and SG (P ≤ 0.02), with RYGB producing larger OXM surges.
The finding that distinguished OXM from other hormones: enhanced postprandial OXM and glicentin responses predicted greater weight loss at 18 months (both P < 0.01) and were associated with larger decreases in energy density preference (P ≤ 0.04). GLP-1, PYY, and ghrelin responses did not predict weight loss outcomes. When all hormones were combined in a model, 60% of the variation in weight loss could be explained.
This suggests OXM plays a distinct role in post-surgical weight loss that goes beyond what GLP-1 alone provides. Patients with the strongest OXM responses not only lost more weight but also shifted their food preferences toward lower-calorie options.
From Natural Peptide to Synthetic Dual Agonists
OXM's 2-8 minute half-life makes it impractical as a therapeutic agent. But its dual receptor profile inspired a class of synthetic GLP-1/glucagon co-agonists now moving through clinical pipelines.[9] Zhihong and colleagues reviewed the emerging landscape of OXM-based analogs in 2023, cataloging modifications like fatty acid conjugation, PEGylation, and amino acid substitutions designed to extend plasma half-life while preserving the balance of GLP-1R and GCGR activation.
Several drugs in development trace their conceptual origin to OXM:
Survodutide (BI 456906, Boehringer Ingelheim) is a GLP-1/glucagon dual agonist that has shown weight loss of up to 19% at 46 weeks in Phase 2 trials, along with liver fat reduction that earned it a focus in MASH research.
Mazdutide (IBI362, Innovent/Eli Lilly) is a mammalian OXM analog with a fatty acid side chain for weekly dosing. Phase 3 data in Chinese populations showed head-to-head superiority over semaglutide in glycemic control.
Cotadutide (MEDI0382, AstraZeneca) was an early clinical-stage GLP-1/glucagon dual agonist, though its development has slowed.
These synthetic descendants validate OXM's core principle: dual agonism targeting multiple metabolic pathways simultaneously can produce outcomes that single-receptor drugs cannot match.
Open Questions and Limitations
Several gaps remain in OXM research:
No dedicated OXM receptor has been identified. Despite decades of study, OXM works exclusively through GLP-1R and GCGR. Whether a specific OXM receptor exists is still debated, and the distinct biological effects of OXM compared to equimolar doses of GLP-1 or glucagon suggest the dual activation pattern creates signaling profiles that neither receptor alone fully explains.[3]
Human clinical trials of native OXM were small and short. The largest interventional studies involved 15-42 participants over 4-6 weeks. The weight loss data, while consistent, comes from studies too small and too brief to draw definitive conclusions about long-term efficacy or safety.
The optimal GLP-1R to GCGR activation ratio is unknown. Scott and colleagues noted that future dual agonist analogs "will require careful balancing of GLP-1 and glucagon receptor activities to obtain optimal effects."[5] Too much glucagon receptor activation could raise blood sugar; too little could sacrifice the energy expenditure benefit. Each synthetic analog in development uses a different ratio.
OXM's distinct effects beyond GLP-1 and glucagon agonism are poorly characterized. Whether OXM activates signaling pathways differently when both receptors are co-activated (biased agonism) versus when each receptor is activated separately remains an open mechanistic question.
The Bottom Line
Oxyntomodulin is a natural gut hormone that activates both GLP-1 and glucagon receptors, reducing appetite through one pathway and increasing energy expenditure through the other. Human studies have confirmed it reduces food intake, promotes weight loss, improves glucose control, and predicts weight loss outcomes after bariatric surgery. Its rapid degradation prevented clinical use, but its dual receptor profile became the template for synthetic drugs like survodutide and mazdutide now in late-stage clinical trials.