Where Does Fat Go When We Lose Weight?

Where Does Fat Go When We Lose Weight?

I bet that 90% of personal trainers, doctors, and nutritionists won't know the answer to this question. You'll be surprised by the answer...

Let's start with the process:

When you put yourself into a calorie deficit, your body starts to use up stored energy reserves, primarily in the form of fat. Since fat is essentially stored energy, our bodies are designed to tap into it when they need extra fuel.

The fat in our bodies is stored as triglycerides inside fat cells (or adipocytes). These triglycerides are like dense energy packets composed of carbon, hydrogen, and oxygen molecules. When your body needs energy but isn't getting enough from food, hormones trigger the breakdown of these triglycerides, starting a process called lipolysis. This is where the fat actually starts to “burn".

When triglycerides are broken down during lipolysis, they split into two main components: fatty acids and glycerol. These fatty acids are then transported to your muscles and other tissues that need energy. But burning these fatty acids for energy doesn’t just make them “disappear”. Instead, they’re metabolised through chemical reactions that transform them into carbon dioxide (CO₂) and water (H₂O) as byproducts.

Here’s where it gets interesting:

• Carbon Dioxide (CO₂):

  About 84% of the fat you lose leaves your body as CO₂ through exhalation. Yep, most of your fat loss actually happens when you breathe out.

• Water (H₂O):

  The remaining 16% of the fat leaves your body as water. This water exits through urine, sweat, and other fluids.

Putting this into perspective, 10 kg (or 22 pounds) of fat loss results in about 8.4 kg of CO₂ being exhaled, with 1.6 kg lost as water [1].

If you’re huffing and puffing during a workout, it’s a good sign that you’re literally breathing away your fat. But just because fat leaves the body through breathing doesn't mean that breathing harder means you lose more fat. It only occurs when your body is in a caloric deficit and the triglycerides in your fat cells are broken down.

Exercise, however, can accelerate this process because working out increases your breathing rate and oxygen consumption. Cardiovascular exercises like running, cycling, or swimming require more oxygen and more exhalation, which can speed up fat oxidation. This is why cardio is often recommended for fat loss.

Cardio does help, but strength training is just as important, if not more. Strength training builds muscle, which increases your resting metabolic rate (the number of calories you burn at rest). A higher metabolic rate helps you maintain a caloric deficit, even when you’re not actively working out.

If you’re looking to maximise fat loss, make sure you’re combining a balanced workout routine with a healthy nutrition plan, adequate hydration, and rest. It’s a journey, but every breath (literally) gets you closer to your goal. Reach out to me to start Personal Training or Online Coaching.

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