How do you burn fat?
- PAIRFS
- 3 days ago
- 3 min read
The real impact of breathing on your metabolism
Why talk about fat burning?
“Burning fat” is one of the most misunderstood topics in sports and health. Many people think that:
It depends solely on the heart rate.
or solely the intensity of the effort,
or that the combustion zone is the same for everyone.
In reality, breathing is the best indicator of the fuel used by your body .
Your breath reveals precisely whether you are burning fat, carbohydrates… or a mixture of both .
1. What exactly is fat burning?
To produce energy, the body can use two main types of fuel:
🔹 Lipids (fats)
very large energy reserve
ideal for long efforts
slow but efficient combustion
requires a lot of oxygen
🔹 Carbohydrates (sugars)
quicker to mobilize
Limited stock (≈ 90 min effort)
combustion that produces more CO₂
majority when intensity increases
👉 Breathing allows us to know in what proportion these two fuels are used.
2. How does breathing reveal your fat burning?
Every time you breathe, you expel CO₂. The amount of CO₂ exhaled depends on the fuel you burn.
✔ Burning fat → low CO₂
The chemical reaction of lipids produces relatively little CO₂.
✔ Burning carbohydrates → lots of CO₂
Carbohydrates generate more CO₂ for the same amount of energy.
By measuring:
ventilation ,
the concentration of exhaled CO₂ ,
the evolution of breathing during exertion,
…we can determine:
➡️ if you are in lipid mode,
➡️ in carbohydrate mode,
➡️ or in a mixed zone.
3. Where is the “fat-burning zone”?
It is below the ventilatory threshold 1 (VT1) .
🔹 Below VT1
Stable breathing
low CO₂ production
combustion primarily of lipids
very economical sector👉 This is the real fat-burning zone .
🔹 Between VT1 and VT2
deeper breathing
mixed combustion of fats and carbohydrates
good area for active endurance
🔹 Above VT2
breathing very rapidly
CO₂ explosion
almost 100% carbohydrates 👉 You are no longer burning fat, but sugar.
4. Why doesn't everyone burn fat at the same rate?
Because the “tipping point” depends on:
your training level,
your ability to use lipids,
your respiratory economy,
your metabolic balance,
your usual training intensity.
Two people of the same age, weight, and heart rate can have:
a very different VT1 ,
a lipid zone of varying size,
much more efficient breathing.
👉 Hence the importance of measuring your thresholds individually , and not using a standard formula.
5. How to improve your ability to burn fat?
✔ 1. Do long sessions below VT1
→ improves lipid oxidation
✔ 2. Increase outings in zone 2 “moderate”
→ enlarges the mixed lipid/carbohydrate zone
✔ 3. Avoid respiratory problems
→ maintain stable ventilation
✔ 4. Monitor your breathing on the ascent
→ avoid drifting too quickly towards carbohydrates
✔ 5. Regularly measure your body fat percentage
→ to track progress
6. How does ZoneX identify your fat-burning zone?
ZoneX real-time measurement:
your ventilation (VE),
your CO₂ production,
your ventilatory transitions (VT1 and VT2).
It then automatically detects:
🔸 the area where you primarily burn fat
→ below VT1
🔸 Your mixed fat/carbohydrate zone
→ between VT1 and VT2
🔸 the moment you switch to carbohydrates
→ above VT2
With ZoneX, you know:
if your session targets the right pathway,
If you are drifting too high,
How to optimize your metabolic endurance.
👉 This is the simplest and most reliable way to actually train your metabolism , and not just your legs.
Conclusion: your breath tells you exactly what your body is burning.
Your breathing is not a simple mechanical movement. It is a direct metabolic indicator , which reveals:
if you burn fat,
when you switch to carbohydrates,
How is your fatigue progressing?
if your pacing is good,
and at what point you are likely to explode.
👉 Understanding your breathing means understanding your metabolism.
👉 And with ZoneX, this understanding becomes simple, precise and immediately actionable.
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