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Longevity University / Lesson 6

Metabolic health hub: insulin resistance, prediabetes and type 2 diabetes

How blood sugar control breaks down, how it is measured (HbA1c, CGMs), what lifestyle trials show, and where GLP-1 drugs fit. Education only.

Published Sources checked 6 sourcesEverstack research teamHow we work

A runner mid-stride on a sand dune, legs only
A runner mid-stride on a sand dune, legs only. Photo: Mitchell Orr, CC0 1.0

Education only, not medical advice. Talk to your clinician before changing medication or if you have a condition.

HbA1c ranges (ADA) and a glucose curveNormal below 5.7%, prediabetes 5.7 to 6.4%, diabetes 6.5% or higher. Glucose rises after meals are normal in healthy people.< 5.7% normal5.7-6.4% prediabetes≥ 6.5% diabetes140mealmealContinuous glucose (illustrative), mg/dL
HbA1c ranges (ADA) and a glucose curve. Normal below 5.7%, prediabetes 5.7 to 6.4%, diabetes 6.5% or higher. Glucose rises after meals are normal in healthy people.

Insulin resistance

In insulin resistance, muscle, liver and fat respond less to insulin, so the pancreas makes more. Type 2 diabetes develops when beta cells can no longer keep up; many organs contribute [1].

The numbers

The American Diabetes Association defines prediabetes as HbA1c 5.7 to 6.4% or fasting glucose 100 to 125 mg/dL, and diabetes as HbA1c 6.5% or higher or fasting glucose 126 mg/dL or higher, confirmed by testing [2]. Only a clinician can diagnose.

CGMs in people without diabetes

In 153 healthy people without diabetes, average CGM glucose was about 98 to 99 mg/dL and time between 70 and 140 mg/dL was 96% [3]. Spikes after meals are normal; one study found even healthy people sometimes reach prediabetic or diabetic ranges [4]. Whether acting on CGM data improves outcomes in people without diabetes is not established.

What works: lifestyle first

In the Diabetes Prevention Program (3,234 adults with elevated glucose), lifestyle change cut diabetes incidence by 58% and metformin by 31% versus placebo [5]. Exercise, weight loss, sleep and fiber-rich whole foods are the foundation.

GLP-1 context

GLP-1 drugs such as semaglutide are prescription medicines. In SELECT, semaglutide reduced major cardiovascular events in people with obesity and heart disease without diabetes [6]. They are not supplements, and nothing Everstack sells is a substitute.

Check your understanding

1. Which HbA1c range does the ADA call prediabetes?
  1. Below 5.7%
  2. 5.7 to 6.4%
  3. 6.5% or higher
Tap to reveal the answer

Answer: b. See [2].

2. In the DPP, which reduced diabetes incidence more?
  1. Metformin
  2. Lifestyle
Tap to reveal the answer

Answer: b. 58% vs 31% [5].

Sources

  1. DeFronzo 2009, Diabetes. doi.org/10.2337/db09-9028
  2. ADA Standards of Care 2025, Section 2. doi.org/10.2337/dc25-S002
  3. Shah et al. 2019, J Clin Endocrinol Metab. doi.org/10.1210/jc.2018-02763
  4. Hall et al. 2018, PLOS Biol. doi.org/10.1371/journal.pbio.2005143
  5. Diabetes Prevention Program 2002, NEJM. doi.org/10.1056/NEJMoa012512
  6. Lincoff et al. 2023, NEJM (SELECT). doi.org/10.1056/NEJMoa2307563

DOIs verified against Crossref on 2026-10-15.

Next: Berberine: a deep dive