Why Am I Not Losing Weight on a GLP-1?

If you've started a GLP-1 and the scale isn't moving the way you expected, you are not imagining it, and you're not doing anything wrong. This is one of the most common questions I get from patients in my practice, and the honest answer is more interesting — and more useful — than "just give it more time."

What's Actually Going On

GLP-1 receptor agonists (think semaglutide, tirzepatide, liraglutide) work in large part by improving how your body handles insulin. But that relationship runs in both directions, and the second direction is the one nobody tells you about:

• GLP-1s improve insulin sensitivity — partly through weight loss, but partly through mechanisms that have nothing to do with the scale at all.

• Insulin resistance, in turn, blunts how well GLP-1s work for weight loss. The more insulin-resistant you are when you start, the smaller your weight-loss response tends to be.

So if you came into treatment with significant insulin resistance — a history of prediabetes, PCOS, elevated fasting insulin, or long-standing metabolic strain — your body may simply need a different strategy than the "average" response you see quoted in drug trials.

The Evidence — Proven

This isn't speculation. A randomized trial in adults with obesity and prediabetes found that liraglutide improved insulin sensitivity within just two weeks — before any meaningful weight loss had occurred — and that effect disappeared when the GLP-1 receptor was blocked. Diet-driven weight loss alone didn't produce the same pattern. In other words, part of what these medications do is independent of the number on the scale.

On the flip side, a 2026 systematic review looking specifically at low or absent responders to GLP-1/GIP therapy identified higher baseline insulin resistance — along with higher starting weight, BMI, and A1c — as consistent predictors of a blunted response. A meta-regression across 47 randomized trials backed this up: higher A1c predicted smaller reductions in weight, BMI, and waist circumference, and people without diabetes lost significantly more weight than people with diabetes on the same medications.

Why This Happens

The leading explanation is compensatory hyperinsulinemia — when your body is insulin resistant, it produces more insulin to compensate, and insulin is a fat-storage, anti-lipolysis hormone. High circulating insulin makes it mechanically harder to release stored fat, even while a medication is working exactly as designed on the appetite and metabolic side.

What This Means for You

The medication may still be working, even if the scale is slow. Weight-independent improvements in insulin sensitivity, inflammation, and liver fat are happening whether or not you're seeing rapid weight change — and those changes matter for your long-term metabolic and cardiovascular health.

Your dose, your labs, and your plan need to be personalized. This is exactly why we don't just write a prescription and check back in three months. In a Direct Primary Care model, I can actually track your fasting insulin, HOMA-IR, and A1c alongside your weight trend, adjust dosing and titration pace based on your real physiology, and layer in the pieces medication can't do alone.

Movement matters more than usual here. Resistance and aerobic exercise both directly improve insulin sensitivity and help preserve the benefit after treatment — the data specifically show that combining exercise with GLP-1 therapy reduces weight regain after stopping.

Who This Especially Applies To

If you have a history of prediabetes, type 2 diabetes, PCOS, or you've simply always felt like your body "fights harder" to lose weight than other people's — this is likely part of your story. It doesn't mean the medication is the wrong choice. It often means your starting point requires more support around it, not less.

Next Step

If you're on a GLP-1 and the results aren't matching your expectations, let's actually look at your numbers instead of guessing. This is the kind of root-cause work we do inside the 12-Week Metabolic Reset — self-guided CGM, data and real education built around your real metabolic picture, not a generic protocol.

You can book a discovery call at attunedirectcare.com if interested in working one-on-one with me through this journey. 

General wellness education only. Not medical advice. Does not establish a physician-patient relationship.