What’s a calorie, when it comes to your body? The official answer is the amount of heat needed to raise a gram of water one degree Celsius. That’s true, and it’s the whole problem. You’ll notice the definition never mentions you.
A calorie is a fact about the food, not about you
Here’s how the number on the wrapper gets made. A sample of the food goes into a sealed steel chamber called a bomb calorimeter. It’s surrounded by water. Somebody ignites it, the food burns completely, the water warms up, and the temperature rise tells you how much energy was in there. That’s it. That’s the number.
Now think about what your body actually does with that same food. It doesn’t ignite it. It digests part of it and passes the rest. How much it pulls out depends on what the food is, what you ate with it, how long you slept, what your hormones are doing this week, and a gut population that isn’t the same as anyone else’s. Two people eat the same sandwich and get two different results, and neither of them gets the number on the label.
So the entire practice of counting calories asks you to do arithmetic on a measurement that was never taken on you. You estimate the input, the app pretends the estimate is real, and then it does the maths with total confidence. Of course it stops working. It never started.
What is actually about you: your mass
Your scale is a measurement of you. Not of the sandwich, not of an average person in a nutrition study, you. Stand on it twice a day at the same two points and you have two real numbers and a real gap between them. Nothing estimated.
That gap is what I call your delta: your weight right after your last meal, minus your weight the next morning before breakfast. Log it for 14 days and the average is a number that’s yours. The whole method is one screen, and the only lever you ever touch after that is tomorrow’s ceiling.
Where the weight actually goes
This is the part that changed how I think, and it’s the one piece of physics I’d ask you to actually sit with. When you lose 10 kg of fat, where does it go?
Most people say heat, or energy, or muscle. Most doctors say the same, which is why two researchers at UNSW published the answer in the BMJ in 2014 after surveying their colleagues. The fat leaves through your lungs. 8.4 kg of every 10 kg of fat you lose is exhaled as carbon dioxide. The other 1.6 kg leaves as water.
It’s a mass balance: the fat molecule is carbon, hydrogen and oxygen, you breathe in oxygen, and the carbon has exactly one exit. Once you’ve read that paper you can’t look at a scale the same way, because the scale is now measuring the one thing that actually moves: mass in, mass out.
Why the mystery feels like a mystery
You’ve probably been told to weigh yourself once, in the morning, and interpret the number. So you step on, see 183.6 after a day you were “good,” and 181.9 after a day you weren’t, and conclude your body is arbitrary. It isn’t. You’re being handed the last frame of a movie and asked what the plot was.
Two readings fix that. The reading after your last meal is your ceiling, the morning reading is your floor, and the gap between them, once you’ve seen it fourteen times, stops being noise and starts being a rate. From there the physics is boring, which is the point: eat and drink until you approach the ceiling, stop, and the delta carries you down overnight.
What this doesn’t claim
It doesn’t claim the overnight drop is fat. Most of it is water and breath, and I say so on the science page. It doesn’t claim your metabolism speeds up. It doesn’t claim you’ll lose what I lost. I lost 40 lbs in a year doing this, and the entire premise is that your body isn’t my body, so your number will be different. It’s yours to find.
Here’s the question I’d leave you with. If a calorie was never a measurement of you, what exactly have you been counting? Find your delta and see what a measurement of you actually looks like.