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Body temperature, metabolism and the slow signals

Some signals move overnight and some take a season. Body temperature deviation, cardiovascular age estimates, weight and energy expenditure belong to the second group, and reading them on a daily timescale mostly produces noise and anxiety.

These posts cover what temperature deviation actually indicates — illness, cycle phase, a hot room, alcohol — and how to tell those apart, along with the metabolic metrics people most often ask about. Several of them exist to push back on a confident claim: that a wearable can measure cortisol, that body composition can be inferred from a ring, that a supplement changed a number when a rolling average says otherwise.

19 articles

Using a ring and a smart scale together (without picking a side)

Most health apps make you choose one ecosystem. A scale measures kilos and body fat; a ring scores recovery. They answer different questions — here is why they should sit on the same page.

6 MIN READ · 24 August 2026

Weighted vest walking: what the bone-density claim actually rests on

Weighted vests are everywhere, mostly sold on bone health. The best trial to test that idea did not find what the marketing promises — here is what it did find.

6 MIN READ · 21 August 2026

Cycle syncing your training: what the data supports and what it doesn’t

Train hard in the follicular phase, back off in the luteal — the advice is everywhere. The performance evidence is weaker than the confidence around it, but your own physiological markers do move. Here is how to tell the two apart using your Oura data.

7 MIN READ · 20 August 2026

Is Polar's SpO2 continuous or on demand? On demand — 45 seconds, when you ask

Polar's own Vantage V3 manual says SpO2 is measured “whenever you want in just 45 seconds”. It is a spot check, not an overnight reading — and Polar states it is not intended for medical use. How that compares with Oura, Garmin, Withings and the rest.

4 MIN READ · 6 August 2026

Does the Ultrahuman Ring PRO have SpO2? Ultrahuman does not say

We checked Ultrahuman's Ring PRO product page, its buy page, its ring FAQ and the field list for its Partner API. None mentions SpO2, blood oxygen or pulse oximetry. Here is what the company does state, and why the Ring AIR is not evidence for the Ring PRO.

4 MIN READ · 6 August 2026

How to run a self-experiment (and actually trust the result)

Tried a supplement, an earlier bedtime or a caffeine cut-off and can't tell if it worked? How an n-of-1 self-experiment measures a habit change against your own baseline — and the traps that fool you.

7 MIN READ · 21 July 2026

Biological age vs chronological age: how to read yours

Your chronological age is fixed; your biological age isn’t. How wearable data estimates the age your body reads at — and which single number matters most.

7 MIN READ · 11 July 2026

Am I healthy? Your Body Score, explained

Vitra's Body page answers one question — am I healthy? — with a single 0–100 Body Score, a seven-system radar, and one plain action for your weakest measure. All computed on your machine from your Oura data.

6 MIN READ · 3 July 2026

Does poor sleep cause weight gain? What the science says

Short, broken sleep nudges appetite, cravings and metabolism in the wrong direction. Here's the evidence linking sleep to weight — and how to watch the connection in your own Oura data.

7 MIN READ · 10 June 2026

On Ozempic or Mounjaro? What your data reveals about GLP-1 weight loss

What GLP-1 drugs (Ozempic, Wegovy, Mounjaro) do to your resting heart rate, HRV and sleep — and how to read those changes against your own Oura baseline so you lose fat, not muscle.

6 MIN READ · 5 June 2026

Your Oura height is rounded — here's why it skews your BMI

Oura reports height to the nearest 10 cm, so 181 cm reads as 180. Here's how that small rounding nudges your BMI and body-fat estimate — and why typing your exact height fixes it.

4 MIN READ · 4 June 2026

How to calculate your TDEE (maintenance calories)

How to calculate your TDEE — your maintenance calories. The Mifflin-St Jeor BMR formula, the activity multiplier, why two calculators disagree, and how to refine the estimate.

6 MIN READ · 4 June 2026

Can your Oura ring detect when you're getting sick?

Can Oura detect illness? Often, yes — a day or two early. Raised temperature, higher resting heart rate and breathing, and suppressed HRV give a heads-up, not a diagnosis.

6 MIN READ · 4 June 2026

BMI vs body fat: which actually matters?

BMI vs body fat — BMI is cheap and population-useful but blind to muscle and fat distribution. Why body-fat percentage and waist tracking track health risk better, and how to read your trend.

6 MIN READ · 4 June 2026

How to lose fat without losing muscle — at a safe pace

How fast should I lose weight? Roughly 0.5–1% of bodyweight a week, with enough protein, lifting and sleep — so the scale drops as fat, not muscle.

6 MIN READ · 4 June 2026

What a low body temperature reading on Oura means

Oura tracks how far your temperature drifts from your own baseline. What a dip below normal can mean — cold room, recovery, cycle phase, alcohol the night before — and when it's nothing.

5 MIN READ · 3 June 2026

Oura SpO2: what blood oxygen means and when to worry

Oura's overnight blood-oxygen reading is a screening signal, not a diagnosis. What a normal SpO2 looks like, what dips can mean (altitude, breathing disruption), and the red flags worth a doctor.

5 MIN READ · 3 June 2026

VO₂ max on Oura: what cardio capacity means and how to raise it

VO₂ max is the best single measure of cardiovascular fitness — and it's age- and sex-relative. What Oura's cardio capacity estimate means, what's good for your bracket, and the training that moves it.

6 MIN READ · 3 June 2026

Your whole body, in one honest number

Most health apps flatter you. A single Body Score that leans toward your weakest system — cardio fitness, HRV, resting heart rate, body composition, activity and sleep — tells you the truth, and where to start.

6 MIN READ · 3 June 2026

About the author

Pedro Thomaz

Pedro Thomaz builds Vitra, a desktop app that reads Oura data against your own baseline instead of a population average. He has worn a ring daily for years and reads these same numbers every morning — which is where most of what is written here comes from. Vitra is not a medical device and nothing on this blog is medical advice.

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