GLP-1 and Insulin Resistance: What the Research Shows

GLP-1 and insulin resistance have become one of the most studied topics in metabolic medicine, with randomized controlled trials now showing that GLP-1 receptor agonists can meaningfully reduce key markers of insulin resistance in people with type 2 diabetes and other metabolic conditions (Frias et al., J Clin Endocrinol Metab, 2024). These medications work through several overlapping pathways—stimulating insulin release, suppressing glucagon, slowing digestion, and reducing appetite—making them distinct from older glucose-lowering drugs (Salvador, Med Clin (Barc), 2025). Lifestyle habits remain the foundation of metabolic health, and GLP-1 medications are prescribed and monitored by clinicians only.

Compare 7 GLP-1 providers side by side →
Or see our $59/month option →

This article walks through how GLP-1 medications act on insulin, glucagon, and appetite, what trials actually measured, and what the evidence still cannot tell us—part of the Flow BioLabs Metabolic Health series.

How Do GLP-1 Receptor Agonists Affect Insulin and Blood Sugar?

GLP-1, or glucagon-like peptide-1, is a hormone released from the gut after eating. It signals the pancreas to release insulin in proportion to the glucose in a meal—a process called glucose-dependent insulin secretion. This means the insulin response is tied to what you just ate, rather than running at a high level all the time (Salvador, Med Clin (Barc), 2025).

GLP-1 receptor agonists are synthetic molecules engineered to mimic or extend this effect. They act on several systems at once:

• Insulin release: They prompt the pancreas to secrete more insulin when blood glucose is elevated after a meal (Salvador, Med Clin (Barc), 2025).
• Glucagon suppression: They reduce glucagon, the hormone that tells the liver to release stored glucose. Lower glucagon means less glucose entering the blood between meals (Mather et al., J Clin Endocrinol Metab, 2024).
• Stomach emptying: They slow how quickly food leaves the stomach, which flattens the post-meal glucose spike (Salvador, Med Clin (Barc), 2025).
• Appetite: They act on brain areas that regulate hunger, reducing overall calorie intake (Salvador, Med Clin (Barc), 2025).

Together, these pathways address several of the mechanisms that drive poor insulin sensitivity. Understanding the relationship between insulin resistance and belly fat helps explain why weight loss from these medications can amplify these benefits further.

What Does the Research Show About GLP-1 and Insulin Resistance?

Finding 1: Semaglutide reduced insulin resistance markers in a large phase 3 trial

A post-hoc analysis of the SURPASS-2 phase 3 trial enrolled 1,879 participants with type 2 diabetes at 128 sites across 8 countries. After 40 weeks, semaglutide 1 mg produced a 5.1% reduction in HOMA2-IR, a standard model-based index of insulin resistance (Frias et al., J Clin Endocrinol Metab, 2024). Improvements in HbA1c and body weight were consistent across baseline HOMA2-IR quartiles, meaning benefits appeared regardless of how insulin-resistant participants were at the start (Frias et al., J Clin Endocrinol Metab, 2024).

Finding 2: Tirzepatide showed greater insulin sensitivity improvements than semaglutide in head-to-head comparisons

In the same SURPASS-2 analysis, tirzepatide—a dual GIP/GLP-1 receptor agonist—reduced HOMA2-IR by 15.5% to 24.0% depending on dose, which was significantly greater than semaglutide’s 5.1% reduction (P < .05) (Frias et al., J Clin Endocrinol Metab, 2024). A separate 28-week double-blind trial at two clinical research centers in Germany also found that tirzepatide produced a greater improvement in insulin sensitivity than semaglutide during a mixed-meal tolerance test (P < .01), with a larger total reduction in insulin secretion rate explained by better underlying sensitivity rather than reduced beta-cell output (Mather et al., J Clin Endocrinol Metab, 2024). This distinction matters: when cells respond better to insulin, the body does not need to produce as much of it.

Finding 3: Semaglutide combined with metformin improved metabolic markers in women with PCOS

A 16-week prospective randomized controlled trial enrolled 100 overweight or obese women with polycystic ovary syndrome (PCOS). Participants assigned to semaglutide plus metformin lost an average of 6.09 ± 3.34 kg, compared with 2.25 ± 4.27 kg in the metformin-only group (P < .01). The combination group also showed greater improvements in testosterone, visceral adiposity index, and C-reactive protein levels (Chen et al., Reprod Biol Endocrinol, 2025). Insulin resistance is a central feature of PCOS, and these metabolic improvements were accompanied by higher rates of menstrual cycle recovery (Chen et al., Reprod Biol Endocrinol, 2025).

For context on the early warning signs that often show up before a diagnosis, see prediabetes symptoms.

GLP-1 and Insulin Resistance: What the Evidence Cannot Yet Tell Us

The research is genuinely promising, but several important limits are worth knowing.

• Most trials are in people with type 2 diabetes or obesity. How well these findings apply to people with milder insulin resistance or other conditions is less clear.
• Long-term durability is still being studied. Most trials run for 28 to 40 weeks. What happens to insulin sensitivity markers over years of use, or after stopping, is not yet fully established (Frias et al., J Clin Endocrinol Metab, 2024).
• Separating drug effect from weight loss is difficult. Much of the improvement in insulin sensitivity seen in trials coincides with significant weight loss. How much is the medication acting directly versus acting through fat reduction is hard to isolate (Mather et al., J Clin Endocrinol Metab, 2024).
• GLP-1 receptor agonists in type 1 diabetes are still being studied. A recent review notes that GLP-1 receptor agonists can improve insulin resistance in type 1 diabetes, but describes current evidence as limited in scope and calls for further study (Apostolopoulou et al., Endocr Rev, 2025).
• Individual response varies. Trials report averages. Within any trial, participants showed a wide range of responses based on their starting metabolic profile (Frias et al., J Clin Endocrinol Metab, 2024).

Poor sleep is one lifestyle factor that can independently worsen insulin sensitivity. The article on the sleep problem hiding inside your cravings explains the hormonal connection.

Common Side Effects and Protecting Muscle During GLP-1 Treatment

GLP-1 receptor agonists are generally well studied, but they do carry side effects. The most commonly reported are gastrointestinal: nausea, vomiting, and diarrhea, particularly at the start of treatment or when doses are increased (Salvador, Med Clin (Barc), 2025). These effects tend to ease over time for most people.

A separate concern during significant weight loss—from any cause—is muscle loss. When the body loses weight rapidly, some of that loss can come from lean mass rather than fat alone. Preserving muscle matters for long-term metabolic health because muscle tissue is a major site of glucose uptake. The evidence on how to protect lean mass while using GLP-1 medications is covered in more detail at GLP-1 and strength training.

Cost is also a practical reality for many people. Access, insurance coverage, and out-of-pocket pricing vary significantly. A breakdown of how to think about those factors is available at GLP-1 cost.

All GLP-1 medications discussed in this article are prescription drugs that require clinician oversight. No dosing information is provided here, and nothing in this article substitutes for personalized medical advice.

How GLP-1 Medications Fit Into a Broader Metabolic Health Plan

GLP-1 receptor agonists are one tool in metabolic health management—not a replacement for the lifestyle habits that form the foundation. GLP-1 receptor agonists complement non-pharmacological approaches including dietary changes and increased physical activity, rather than substituting for them (Młynarska et al., Int J Mol Sci, 2025).

This article is part of the Flow BioLabs Metabolic Health series. For a related look at how meal timing affects blood sugar, see early time-restricted eating.

Post-meal movement is another low-barrier habit with evidence behind it. Short walks after eating help muscles take up glucose from the blood. These habits do not replace medical treatment but they work in the same direction, and the research suggests they matter regardless of whether someone is on medication.

If you are curious about your own metabolic starting point, the free Metabolic Friction Assessment is a practical place to begin.

5 Habits That Support GLP-1 and Insulin Resistance Goals

• Take a short walk after meals. Even a 10-minute walk after eating can help blunt post-meal blood sugar rises, which works in the same direction as GLP-1 medication effects on glucose.
• Prioritize protein at each meal. Adequate protein helps preserve lean muscle mass during weight loss, which is especially important if significant weight change is occurring.
• Protect your sleep. Disrupted or insufficient sleep can worsen insulin sensitivity independently of diet and medication, so consistent sleep habits remain part of the metabolic picture.
• Include resistance training regularly. Muscle tissue is a major site where glucose is taken up from the blood; keeping or building muscle supports insulin sensitivity over the long term.
• Work with your clinician on monitoring. Regular check-ins on blood sugar markers, weight, and side effects help ensure any medication is working safely and effectively for your situation.

Want to see how your body signals fit together? Try the free Signal Map quiz.

Related reading: Insulin resistance belly fat | Fatty liver symptoms

On a GLP-1 medication? The GLP-1 Companion: Muscle Defense System lays out protein, strength training and daily habits that help you keep muscle while the scale moves.

Frequently Asked Questions

How does GLP-1 improve insulin resistance?

GLP-1 receptor agonists stimulate insulin release in a meal-dependent way, suppress glucagon, slow stomach emptying, and reduce appetite. Together these effects lower blood sugar and, over time, reduce the degree to which cells resist insulin’s signals. Weight loss driven by these medications likely amplifies the benefit.

Do GLP-1 medications work for insulin resistance without type 2 diabetes?

Most of the clinical trial evidence for GLP-1 and insulin resistance comes from people with type 2 diabetes or obesity-related conditions like PCOS. Evidence in people with milder insulin resistance who do not have these diagnoses is more limited. A clinician can help determine whether these medications are appropriate for a given situation.

What are the most common side effects of GLP-1 receptor agonists?

Nausea, vomiting, and diarrhea are the most frequently reported side effects, particularly when starting or increasing the dose. For many people these ease over several weeks. Muscle loss during rapid weight loss is another consideration worth discussing with a clinician.

Are GLP-1 medications a replacement for diet and exercise?

No. The research and clinical guidance consistently frame GLP-1 receptor agonists as complementary to dietary changes, physical activity, and other lifestyle habits—not as a substitute for them. Lifestyle habits remain the foundation of long-term metabolic health.

Comparing GLP-1 options? Our GLP-1 cost guide compares current prices for brand-name and compounded options so you can have an informed conversation with your clinician. See the GLP-1 cost comparison →

Sources

1. Frias JP, De Block C, Brown K, et al. Tirzepatide Improved Markers of Islet Cell Function and Insulin Sensitivity in People With T2D (SURPASS-2). J Clin Endocrinol Metab. 2024. doi:10.1210/clinem/dgae038
2. Salvador J. GLP-1-based medications: Mechanisms involved in obesity treatment. Med Clin (Barc). 2025. doi:10.1016/j.medcli.2025.107035
3. Mather KJ, Mari A, Heise T, et al. Effects of Tirzepatide vs Semaglutide on β-Cell Function, Insulin Sensitivity, and Glucose Control During a Meal Test. J Clin Endocrinol Metab. 2024. doi:10.1210/clinem/dgae319
4. Chen H, Lei X, Yang Z, et al. Effects of combined metformin and semaglutide therapy on body weight, metabolic parameters, and reproductive outcomes in overweight/obese women with polycystic ovary syndrome: a prospective, randomized, controlled, open-label clinical trial. Reprod Biol Endocrinol. 2025. doi:10.1186/s12958-025-01447-3
5. Apostolopoulou M, Lambadiari V, Roden M, et al. Insulin Resistance in Type 1 Diabetes: Pathophysiological, Clinical, and Therapeutic Relevance. Endocr Rev. 2025. doi:10.1210/endrev/bnae032
6. Młynarska E, Czarnik W, Dzieża N, et al. Type 2 Diabetes Mellitus: New Pathogenetic Mechanisms, Treatment and the Most Important Complications. Int J Mol Sci. 2025. doi:10.3390/ijms26031094

This article is for education only and is not medical advice. Talk with your healthcare professional before changing your health routine.

Compare 7 GLP-1 providers side by side →
Or see our $59/month option →