Multi-receptor agonists (dual GIP/GLP-1, dual glucagon/GLP-1, and triple agonists) produce greater weight loss than single GLP-1 drugs because each additional receptor target adds complementary mechanisms — from enhanced appetite suppression to increased fat burning.
1 → 2 → 3 receptor targetsEach step up in receptor targeting adds new anti-obesity mechanisms: GLP-1 alone reduces appetite; adding GIP enhances metabolism; adding glucagon increases energy expenditure and fat burning — explaining the progressive increase in weight loss efficacy.
What the researchers found
This review explains the mechanisms behind why multi-receptor agonists produce greater weight loss than single GLP-1 agonists alone in non-diabetic obese adults. The dual GIP/GLP-1 agonist tirzepatide activates both receptors, enhancing appetite suppression and metabolic effects beyond what GLP-1 alone achieves. GLP-1/glucagon dual agonists add glucagon's ability to increase energy expenditure and fat burning. Triple GLP-1/GIP/glucagon agonists combine all three mechanisms — appetite reduction, enhanced metabolic rate, and improved fat utilization — potentially offering the greatest weight loss of all. Each additional receptor target adds complementary mechanisms that address different aspects of energy balance.
Why it matters
The evolution from single to dual to triple agonists represents one of the most rapidly advancing areas of drug development. Understanding why adding GIP and/or glucagon signaling to GLP-1 therapy improves outcomes is essential for clinicians choosing between available medications (semaglutide vs. tirzepatide) and for the pharmaceutical industry developing next-generation drugs (retatrutide and others). The mechanistic explanations also help predict potential side effects and identify which patients might benefit most from each approach.
The numbers in context
3 multi-receptor platforms reviewed: GLP-1/GIP, GLP-1/GCG, GLP-1/GIP/GCG · FDA-approved: liraglutide, semaglutide (mono), tirzepatide (dual)
How the study worked
Narrative review summarizing the pharmacological mechanisms of GLP-1 mono-agonists, GLP-1/GIP dual agonists, GLP-1/glucagon dual agonists, and GLP-1/GIP/glucagon triple agonists for obesity. The review synthesizes evidence from preclinical and clinical studies to explain the mechanistic basis for the enhanced weight loss efficacy of multi-receptor targeting.
Who was studied
Not applicable — review of mechanisms for multi-receptor agonists in obese adults without type 2 diabetes
What this study cannot tell us
As a narrative review, this does not perform systematic literature search or meta-analysis. Head-to-head clinical trials directly comparing all these drug classes are limited. The review focuses on non-diabetic obesity, and the mechanisms may differ in patients with type 2 diabetes. Triple agonists (like retatrutide) have limited clinical data — most evidence is from early-phase trials. Long-term safety data for dual and triple agonists is still accumulating.
How to read the evidence
This is a comprehensive narrative review synthesizing preclinical and clinical evidence. The mechanistic explanations are well-supported by published literature. However, the review doesn't perform systematic analysis, and direct head-to-head comparison data between all drug classes is limited.
When this study was published
Published in 2025 in Diabetes, Obesity & Metabolism, this review is timely and relevant as the field rapidly transitions from single to multi-receptor agonists. The mechanistic framework it provides will remain useful as new drugs enter clinical practice.
The bigger picture
The incretin drug landscape is evolving at unprecedented speed. Semaglutide (single GLP-1 agonist) dominated 2023-2024, tirzepatide (dual GIP/GLP-1) is rapidly gaining ground, and triple agonists like retatrutide are in clinical development. Understanding the mechanistic basis for each approach is crucial as the field moves toward even more complex multi-receptor drugs. This review provides the biological framework for understanding why this evolution is happening and what the theoretical ceiling of pharmacological weight loss might be.
Questions still open
- Is there a point of diminishing returns — will quadruple or quintuple agonists offer meaningful additional benefit beyond triple agonists?
- Do the additional mechanisms (glucagon-mediated energy expenditure, GIP effects) also increase the risk of side effects like muscle loss or hepatotoxicity?
- Which patient phenotypes benefit most from each multi-receptor combination — is it possible to personalize treatment selection?
Common questions
Is tirzepatide better than semaglutide for weight loss?
What are triple agonists and when will they be available?
Read the original research
Why does GLP-1 agonist combined with GIP and/or GCG agonist have greater weight loss effect than GLP-1 agonist alone in obese adults without type 2 diabetes?
Diabetes, obesity & metabolism, 27(3), 1079-1095
Citation
Jiang, Yuchen; Zhu, Huijuan; Gong, Fengying. (2025). Why does GLP-1 agonist combined with GIP and/or GCG agonist have greater weight loss effect than GLP-1 agonist alone in obese adults without type 2 diabetes?. Diabetes, obesity & metabolism, 27(3), 1079-1095. https://doi.org/10.1111/dom.16106