What is metabolic health?
Metabolic health includes glucose, blood pressure, lipids and other clinical factors. A glucose trace alone does not assess energy levels or establish overall health.
In a nationally representative analysis of US survey data (NHANES), only 6.8% of American adults had optimal cardiometabolic health in 2017–2018, down from 1999–2000 (O'Hearn et al., Journal of the American College of Cardiology, 2022). That study defined optimal cardiometabolic health by adiposity, blood glucose, blood lipids, blood pressure and absence of cardiovascular disease, which is not the same as the five markers listed below. The figure is a population estimate, not a measure of any one person's metabolic health.
Cardiometabolic risk has several dimensions and causes. A glucose trace alone cannot identify the cause of diabetes, cardiovascular disease, fatty liver disease or other conditions.
The five markers of metabolic health
The thresholds below illustrate the specific research definition used by Araújo and colleagues (NHANES 2009–2016), not one universal clinical definition. O’Hearn’s later analysis used a different definition including cardiovascular disease history. Neither study diagnoses every adult outside its optimal category.
Why glucose is central to metabolic health
CGM measures the glucose dimension only. It does not measure lipids, blood pressure, insulin, adiposity or overall metabolic health; other clinical assessments remain necessary.
Insulin resistance — the root problem
Insulin resistance can contribute to altered glucose regulation, but causes and clinical presentations vary. CGM does not directly measure insulin sensitivity or establish an individual mechanism.
CGM is not a screening or diagnostic test for insulin resistance, prediabetes or diabetes. Post-meal peaks also occur in healthy people; laboratory testing and clinical evaluation are needed.
Glucose variability — not just averages
Laboratory HbA1c reflects longer-term glucose exposure; fasting plasma glucose is a measurement at one time. Neither is identical to a CGM average. Glucose variability — the amplitude and frequency of glucose swings — is an active area of research. In controlled laboratory experiments in healthy volunteers and people with type 2 diabetes, glucose oscillating between 5 and 15 mmol/L over 24 hours produced more endothelial dysfunction and oxidative stress than a constant high glucose level (Ceriello et al., Diabetes, 2008). Those are short-term experimental markers; they do not show that ordinary post-meal swings in people with normal average glucose cause cardiovascular events.
Whether the smaller swings seen after ordinary meals affect long-term health has not been established. Many people use CGM to see which meals and habits produce larger or smaller swings in their own readings.
Understanding glucose spikes
“Spike” is a descriptive or app-specific term without a universal diagnostic rise threshold. A sensor glucose excursion alone does not diagnose disease or measure insulin secretion.
What causes glucose spikes?
Glucose responses to similar foods can vary. A post-meal sensor peak does not establish insulin secretion, overall nutritional quality or the cause of a metabolic condition.
In Shukla 2015, 11 metformin-treated adults with type 2 diabetes ate the same meal in different orders in a small crossover study. Measured post-meal glucose was lower when vegetables and protein preceded carbohydrate. This does not establish a universal percentage reduction, a weight-loss benefit or a long-term result.
Meal timing and sensor glucose may be associated. A personal trace does not measure circadian insulin sensitivity or prove that every breakfast produces a lower peak than dinner.
Stress, sleep and glucose may be related, but a personal sensor trace cannot prove cortisol or sleep caused a particular change.
In Reynolds 2016, 41 adults with type 2 diabetes completed a randomized crossover comparison: three ten-minute walks after meals versus one thirty-minute daily walk. Post-meal incremental glucose exposure was about 12% lower overall and 22% lower after the evening meal. This was not a comparison with no walking or a guarantee for everyone.
Laboratory glucose and HbA1c ranges
Prediabetes and diabetes are diagnosed with laboratory tests. The ranges below are the American Diabetes Association criteria for fasting plasma glucose and HbA1c (ADA Standards of Care 2026, Section 2). They are laboratory ranges, not CGM targets.
| Laboratory test | Below the prediabetes range | Prediabetes range | Diabetes range |
|---|---|---|---|
| Fasting plasma glucose (no calories for at least 8 hours) | <100 mg/dL | 100–125 mg/dL | ≥126 mg/dL |
| HbA1c | <5.7% | 5.7–6.4% | ≥6.5% |
These are laboratory criteria and do not apply to CGM readings. The ADA states that there is currently insufficient evidence to support the use of continuous glucose monitoring for screening or diagnosis of prediabetes or diabetes, so CGM-derived values such as post-meal peaks, rise above baseline, time in range and glucose variability have no diagnostic cut-offs. Healthy adults wearing CGM regularly reach post-meal values above 140 mg/dL: in a 2024 study of 36 participants without diabetes the median post-meal peak was 140 mg/dL and the 90th percentile was close to 180 mg/dL (Freckmann et al., 2024). Glucose targets for people with diabetes should be individualized with a healthcare provider.
How to improve metabolic health
Discuss nutrition, activity, sleep and other risk factors with a healthcare professional. CGM observations concern glucose only and do not prove an overall metabolic benefit.
Post-meal walking
In Reynolds 2016, 41 adults with type 2 diabetes completed a randomized crossover comparison: three ten-minute walks after meals versus one thirty-minute daily walk. Post-meal incremental glucose exposure was about 12% lower overall and 22% lower after the evening meal. This was not a comparison with no walking or a guarantee for everyone.
Food order at meals
In Shukla 2015, 11 metformin-treated adults with type 2 diabetes ate the same meal in different orders in a small crossover study. Measured post-meal glucose was lower when vegetables and protein preceded carbohydrate. This does not establish a universal percentage reduction, a weight-loss benefit or a long-term result.
Resistance training
Resistance training is part of standard physical-activity guidance: the American Diabetes Association recommends 2–3 sessions per week on nonconsecutive days for adults with type 1 or type 2 diabetes (ADA Standards of Care 2026, Section 5). Muscle takes up glucose after meals, so building and maintaining muscle supports glucose metabolism. How large and how long the effect of a single session is varies between people.
Sleep optimization
Sleep is one of the lifestyle factors that influence glucose regulation. In a small controlled study, nine healthy adults who were allowed only four hours of sleep for one night had lower insulin sensitivity the next day: the glucose infusion rate needed during a clamp test fell by about 25%, while fasting glucose was unchanged (Donga et al., Journal of Clinical Endocrinology & Metabolism, 2010). That is a laboratory measure of insulin sensitivity after one restricted night, not a fixed loss of meal tolerance after every poor night.
Time-restricted eating
Time-restricted eating is a separate intervention whose suitability depends on treatment and individual circumstances. A CGM trace cannot establish fat burning, an optimal eating window or a promised improvement within weeks.
Vinegar before carbohydrate-rich meals
Small trials have tested vinegar taken before a meal. In a crossover trial in 11 adults with newly diagnosed type 2 diabetes who took no glucose-lowering drugs, 30 ml of vinegar (6% acetic acid) diluted in water before a mixed meal lowered total glucose exposure over five hours by about 6% compared with water (area under the curve 2,834 vs 3,005 mmol/L·min) (Mitrou et al., Journal of Diabetes Research, 2015). The size of the effect depends on the measure used, the meal and the people studied. In a pilot study in people with type 1 diabetes and gastroparesis, apple cider vinegar slowed gastric emptying further, which the authors noted might be a disadvantage for glycaemic control (Hlebowicz et al., BMC Gastroenterology, 2007). Vinegar is not a treatment; talk to your clinician before using it if you have diabetes or take glucose-lowering medication.
Using CGM to optimize metabolic health
CGM shows interstitial glucose alongside logged events. Associations in one person’s trace do not prove a meal, activity, sleep or stress caused the change. Glucose alone does not measure insulin, fat burning, energy availability or overall metabolic health.
Dexcom Stelo is an over-the-counter device for people aged 2 years and older who do not use insulin, with caregiver supervision below 18. It is not intended for problematic hypoglycemia or dialysis and has no clinical high/low alarms. Platform enrollment may have narrower eligibility. Lingo remains an adult OTC device. These indications do not establish a benefit for every wellness user or replace clinical care.
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io Gut Health is an advertised product. No product-specific metabolic-health benefit is established by the studies described here.