Consumer access to advanced diagnostics has expanded faster than most people's ability to interpret them. DEXA scans, continuous glucose monitors, and VO2 max testing each have a real role — and each gets stretched into claims they cannot quite support. Worth understanding what each one is genuinely good for, and where to stay skeptical.
The appeal of advanced diagnostics
These tests promise precision: a number, a picture, a curve. Precision is genuinely useful when it changes a decision. It is less useful — and sometimes counter-productive — when it produces a dashboard that you stare at without acting on.
DEXA: body composition and bone context
DEXA is most commonly known as a bone density assessment and is also used to estimate body composition (fat mass, lean mass, regional distribution). For bone health it is well-established as a clinical tool. For body composition, it offers a more granular view than a scale or impedance device, but the results still need interpretation — and the most useful version is usually trend over time, not a single scan.
CGM: glucose response and pattern awareness
Continuous glucose monitors were developed for people with diabetes. In non-diabetic use, they can offer awareness — how a particular meal, workout, or night of poor sleep shifts your glucose curve. That awareness can change behavior, especially around ultra-processed foods and late-night eating.
What CGM is not: a diagnostic. Non-diabetic glucose excursions vary widely and do not, on their own, establish a metabolic condition. Short, intentional CGM experiments are a more honest framing than 'continuous monitoring forever.'
VO2 max: cardiorespiratory fitness
Cardiorespiratory fitness is one of the most consistently meaningful health signals across the literature, and the AHA has called for clinicians to assess it routinely. A laboratory VO2 max test gives the most accurate snapshot; wearable estimates are less precise but useful for tracking trend if you train consistently.
Improvement comes from training, not testing.
What these tests do not solve
None of these tests replace the behavioral basics: activity, sleep, nutrition pattern, strength, blood pressure, lipids. They can sharpen the picture. They cannot substitute for the work.
How to decide what is worth doing first
A useful order of operations for most adults:
- Confirm the basics: routine bloodwork and blood pressure with a clinician.
- Build the behaviors: consistent activity, sleep, and nutrition pattern.
- Add a diagnostic when it will answer a specific question — bone density concern, training plateau, persistent fatigue, family history.
- •DEXA, CGM, and VO2 max each have legitimate uses — and each can be over-marketed.
- •The best diagnostic is one whose result you can act on with a qualified clinician or coach.
- •Interpreting non-diabetic CGM data as evidence of disease.
- •Treating a single DEXA reading as a verdict on body composition.
- •Buying repeat testing before changing the underlying behavior.
- •What question is this test answering for me?
- •Who will help me interpret the result?
- •What would I do differently based on the outcome?
This Field Note is for educational purposes only and is not medical advice, diagnosis, treatment recommendation, or individualized health guidance. Always consult a qualified healthcare professional before making health decisions.