How we humans know exact (very close) amount calories in different foods? Is there a machine in the very start of humans learning calories?

The BIGGEST problem is that now there's lots of calories of Junk Food around - like sugar - that mankind never had before. It makes people sick and fat - but sugar also makes you want to eat MORE.

If you ate real food - like cabbage and beans and a little meat, you normally just stop when you're "full"....... but when you eat Sugar this and Sugar that for dinner, there's just no end. You don't get "full" - the Sugar just tells you to eat more.

This is great for corporate profits - as you might imagine. And it's being translated into a tidal wave of obesity and diabetes headed our way.

There is a myth that a "calorie is a calorie"...... but it ain't true. A calorie of real food feeds you - a calorie of Sugar makes you sick and fat and a burden on the medical establishment.

Expanding on the previous answer, one Calorie is defined as the amount of energy (or heat) required to raise one liter of water by one degree Celsius. By testing this, Calorie counts can be determined.

Calories are calculated by burning the food and seeing how much energy it releases.