[gumby]

There's more to digestion and metabolism than basic thermo. I mean sure, supply your body with inadequate calories and it will make up the difference by pulling by storage. But that's like saying the steam train and diesel turbine train work the same way: just heat up a fluid to move some metal to turn a crankshaft.

The food labels on your food packages are determined by calorimetry. But your body digests some food more readily than other foods, also affected by what else you eat with it, how you prepare it, etc. Also your body encourages you to eat certain things to get various nutrients: you rarely eat those nutrients alone; typically they come along with a bunch of other stuff. Then peoples' feedback systems are heavily influenced by all sorts of things: signals from your gut biome, your emotions and response to social signals and learning, various kinds of signalling reflecting what you eat (and those signals are empirically hacked by food engineers), and random brain bugs, among others.

Exercise is hardly scientifically measurable either. It's not like that "calories burned" reading on your bike, is comparable to a bike from a different manufacturer, much less a different kind of exercise.

[bostonsre]

It's hard to be precise about it, but that doesn't mean it's impossible. If you are gaining weight on your current caloric intake and exercise regiment, lower the amount of calories you are eating. Being an advanced sniper that takes into account all the various impacts of physics is great and can work, or you can use tracer bullets and walk in your shot with a simple ooda loop.