A good primer on this topic is the Maintenance Phase podcast episode ‘The Trouble with Calories’: https://maintenancephase.buzzsprout.com/1411126/10671811
Prefer reading? The sources list for that episode is full of goodies:
History of the Calorie in Nutrition
Caloric Equivalents of Gained or Lost Weight
The Foreign Policy of the Calorie
Why the most popular rule of weight loss is completely wrong
The energy balance model of obesity: beyond calories in, calories out
“Calories in, calories out” and macronutrient intake
Calories on food packets are wrong—it’s time to change that
Why Does the FDA Recommend 2,000 Calories Per Day?
Who Actually Needs a 2,000 Calorie a Day Diet?
The Nutrition Facts Label: Its History and Updates
It doesn’t stop there though, almost everything we think we know about nutrition is kind of bullshit.
You need 2000-2500 calories a day? There’s no evidence to support that claim. It’s fully a made up number.
Calories in - calories out = weight gain or loss’? Absolute bullshit. No credible scientist believes this anymore. Your body compensates for dieting in like a billion ways to the point where reducing calorie intake often results in long term weight gain.
2 liters of water per day? Again: a made up number. ZERO evidence.
The BMI? Not remotely based on science. Absolute bullshit.
Being ‘overweight’ or ‘obese’ is bad for you? Heavily disputed for all but the highest weight categories.
And of course: there is no evidence based way to lose weight and keep it off. The idea that people can decide to be thinner if not supported by evidence. Almost every study shows that almost all humans just keep returning to their set weight again and again.
Vitamin supplements? We still don’t really know why they sometimes work and sometimes don’t. Your body seems to decide whether to absorb them pretty much on a whim.
It all falls apart the moment you go looking for evidence. It’s such a sham.