Research goal
Appetite & Weight Management
Covers compounds researched for their effects on satiety signalling, appetite regulation, gastric emptying, and sustained weight management through incretin and related pathways.
Relevant Compounds
| Compound | Class | Primary mechanism | Commonly reported for | Link |
|---|---|---|---|---|
| Retatrutide | GLP-1/GIP/Glucagon triple agonist | Appetite suppression via triple incretin pathway + energy expenditure increase | Maximum appetite suppression, weight management | View profile → |
| Tirzepatide | GLP-1/GIP dual agonist | Dual incretin agonism; superior satiety vs GLP-1 alone; GIP reduces nausea | Appetite control with better GI tolerability | View profile → |
| Semaglutide | GLP-1 agonist | GLP-1 receptor agonism; delays gastric emptying; CNS appetite centres | Appetite suppression, weight management, established efficacy | View profile → |
Research Context
GLP-1 (glucagon-like peptide-1) is an incretin hormone released from intestinal L-cells in response to nutrient ingestion. Its appetite-suppressing effects operate through two anatomically distinct pathways: peripherally, GLP-1 slows gastric emptying, extending the mechanical sensation of fullness; centrally, GLP-1 receptors in the hypothalamic arcuate nucleus and the brainstem area postrema directly modulate appetite signalling. Pharmacological GLP-1 receptor agonists amplify both pathways with a longer duration of action than endogenous GLP-1, which has a half-life of only minutes. This dual peripheral-central mechanism distinguishes GLP-1 agonism from earlier appetite-modulating pharmacological approaches and explains the sustained appetite suppression observed in clinical trials.
The addition of GIP (glucose-dependent insulinotropic polypeptide) co-agonism, as in tirzepatide, introduces a second incretin pathway with distinct receptor pharmacology. GIP receptors are expressed on pancreatic beta cells and in adipose tissue; GIP co-agonism enhances insulin secretion in a glucose-dependent manner and modulates adipose lipid handling. Crucially, GIP receptor activation appears to counteract the nausea induced by GLP-1 receptor agonism — a GI tolerability advantage that is mechanistically supported and clinically observed in head-to-head comparisons. The SURPASS clinical programme demonstrated that tirzepatide produces superior HbA1c reductions and greater weight loss than semaglutide at maximum doses, attributed to this dual pathway engagement.
Retatrutide adds a third receptor target: glucagon receptor agonism. Glucagon's effects in this context are distinct from its hyperglycaemic role in type 1 diabetes; at the doses and receptor ratios designed into retatrutide, glucagon receptor activation is believed to increase hepatic glucose output (partially offset by the GLP-1 insulin-stimulating component) and, more significantly, to activate brown adipose tissue thermogenesis — increasing energy expenditure beyond what appetite suppression alone achieves. Phase 2 trial data for retatrutide reported mean weight loss exceeding 17% at 48 weeks, the highest published figure for any incretin-class compound at the time. This energy expenditure dimension represents a meaningful mechanistic advance over dual agonists.
Compound Notes
Retatrutide
Retatrutide (LY3437943) is Eli Lilly's investigational triple agonist targeting GLP-1R, GIPR, and glucagon receptor simultaneously. Phase 2 trial data published in 2023 demonstrated mean body weight reductions of approximately 17–24% at 48 weeks depending on dose, the highest efficacy signal in the incretin class at the time of publication. Its glucagon receptor component adds an energy expenditure dimension — brown adipose thermogenesis — absent from dual agonists. Research has investigated Retatrutide for its potential role in obesity and metabolic disease; it remains under Phase 3 development and is not yet approved. The triple agonism also makes it among the most potent appetite suppressants in the class, though tolerability data from larger trials is still emerging.
Tirzepatide
Tirzepatide (Mounjaro / Zepbound, Eli Lilly) is FDA-approved for type 2 diabetes and obesity. Its dual GLP-1/GIP agonism produces superior clinical outcomes to GLP-1 mono-agonism: the SURPASS programme demonstrated greater HbA1c reduction and weight loss versus semaglutide, and the SURMOUNT programme reported mean weight reduction of approximately 15–22% in obesity trials depending on dose. GIP co-agonism is associated with improved GI tolerability compared to GLP-1 mono-agonism, an important practical consideration in clinical and research use. Reported side effects in research and anecdotal accounts include nausea, vomiting, diarrhoea, and constipation, consistent with the incretin class, though generally lower in incidence than with semaglutide monotherapy.
Semaglutide
Semaglutide (Ozempic / Wegovy / Rybelsus, Novo Nordisk) is FDA-approved for type 2 diabetes and obesity and has the longest established clinical history in the modern incretin class. The SUSTAIN programme established its glycaemic efficacy; the STEP programme (2.4 mg SubQ weekly) demonstrated approximately 15% mean weight reduction at 68 weeks. The SELECT trial additionally demonstrated significant cardiovascular event reduction in adults with obesity and established cardiovascular disease — data that extends semaglutide's evidence base beyond metabolic outcomes. Reported side effects in research and anecdotal accounts include nausea, vomiting, diarrhoea, and constipation. Weekly SubQ and oral formulations are both approved.
Commonly Reported Combinations
The compounds on this page are not commonly reported in combination with one another — combining incretin agonists of different classes carries substantial risks of additive nausea, vomiting, and hypoglycaemia and is not supported by clinical trial data. They are typically studied and reported as monotherapy agents.
In research and anecdotal contexts, incretin agonists are sometimes reported alongside compounds targeting body composition from a different angle — for example, GH secretagogues for lean mass preservation during caloric deficit. This combination logic is discussed on the Fat Loss & Metabolic Recomposition goal page.
Frequently Asked Questions
How do GLP-1 agonists reduce hunger — CNS mechanism or gastric mechanism?
Both pathways operate simultaneously but are anatomically distinct. Peripherally, GLP-1 receptor activation in the enteric nervous system and stomach wall slows gastric emptying, prolonging the physical distension of the stomach after eating and extending the sensation of fullness. Centrally, GLP-1 receptors in the hypothalamic arcuate nucleus reduce NPY/AgRP neuron activity (the hunger-driving neurons) and increase POMC/CART neuron activity (the satiety neurons); receptors in the brainstem area postrema also integrate satiety signals. This central component is particularly important for the sustained appetite suppression observed clinically, as it persists independently of gastric content. Vagal afferent signalling connects the peripheral and central pathways.
Why does tirzepatide produce less nausea than semaglutide?
The GIP receptor component of tirzepatide appears to exert a gastric tolerability benefit that attenuates the nausea associated with GLP-1 receptor agonism. The precise mechanism is not fully elucidated, but GIP receptor activation in the gut and brainstem is believed to modulate the emetic signalling that GLP-1 agonism can trigger, particularly at higher doses or during dose escalation. This is supported by clinical observations in the SURPASS trials, where tirzepatide — despite producing superior weight loss and glycaemic control — demonstrated comparable or lower rates of nausea and vomiting versus semaglutide at effective doses. The GIP component may also independently moderate gastric emptying kinetics.
What does glucagon receptor agonism add to appetite management in Retatrutide?
The glucagon receptor component of Retatrutide adds an energy expenditure dimension that is absent from GLP-1 and GLP-1/GIP compounds. Glucagon receptor activation stimulates brown adipose tissue thermogenesis — increasing basal metabolic rate by activating thermogenic fat cells that dissipate energy as heat rather than storing it. This effect is distinct from appetite suppression and represents a second mechanism of weight reduction operating on the energy expenditure side of the energy balance equation. The GLP-1 component in Retatrutide is required to offset the hyperglycaemic effect that isolated glucagon agonism would otherwise produce, making the triple combination pharmacologically deliberate rather than additive.
What does research show about long-term weight regain after stopping these compounds?
Post-discontinuation weight regain is well-documented across the incretin class. The STEP 4 extension study, which examined outcomes after stopping semaglutide, found that participants regained approximately two-thirds of their lost weight within one year of stopping treatment. Similar patterns have been observed with tirzepatide. This is mechanistically expected: incretin agonists suppress appetite via pharmacological receptor occupancy, and once the drug is cleared, the underlying regulatory system reverts to its baseline state. The research framing of these compounds as chronic medications rather than finite courses reflects this pharmacological reality. Behavioural and dietary interventions initiated during treatment may partially mitigate but do not eliminate rebound.