I agree it’s not possible to count exactly how many calories you burn. The basic idea is you guess how many you burn and consume that amount of calories each day. If over weeks/months you are gaining weight then you are eating too many calories, and you adjust, until your weight is stable. Now you know roughly how many your burn in a day. It’s literally that simple.
1000 calories of pizza and 1000 calories of broccoli is the exact same from a weight gain point of view. If your maintenance calories are 2000, and you eat exactly 2000 calories of pizza, and only pizza, you will not gain weight. You’ll be extremely unhealthy in other ways due lack of proper vitamins.
Also 2000 calories of pizza is doable in one sitting, and you won’t feel very full so it would be easy to eat more, but good luck eating 2000 calories of broccoli in a day, the volume of food is much higher.
Do you have a link to the mice study? That sounds interesting.
How am I admitting it’s more than CICO? What I said aligns directly with CICO. If you eat junk, you are eating high calorie dense foods, and people tend to eat more because it’s not as filling. That’s literally CICO. You eat more calories, and you gain weight.
The reason dieticians recommend not actually counting calories is because people suck at it, as was mentioned before. By telling them to eat healthy, low calorie foods, it makes it basically impossible to eat too many calories due to the giant volume of food you would need to eat.
In the end it all boils down to calories. You cannot escape the laws of physics. You can’t gain mass without adding mass.