The problem is measuring calories out. Often it is recommended to use an average value for your build and call it good. But this is not a very good model imho, and involves a lot of guesswork.
Estimation of one's TDEE is pretty simple. Once you have a starting point, adjustment is common sense. If you're not losing weight at the rate you expect, lower your TDEE and thus lower your caloric budget. Now, adding cardio into the mix is where things can go off the rails. One reason cardio can be BAD for a diet is precisely because it is hard to measure how many calories you burn while exercising. Estimate too low and you end up in much too deep of a deficit to maintain the diet. Estimate too high and you're not losing as much weight as you want. These problems are easily solved over a long run if you can accurately do approximately the same amount cardio each time you do it, but this is also quite hard.
Cardio is great for heart health and overall wellness. It's crap for losing weight effectively, IMO. The absolute easiest way to lose weight is to simply estimate your TDEE requirements using a sedentary activity level, eat at a 3,500 calorie deficit each week, preferably at 500 calories per day or cycled if you are lifting weights, and adjust accordingly.
Here is another stable algorithm for losing weight, which is fully compatible with cardio.
Choose a desired rate of weight loss and a measurement period. Each period, measure your inputs and do the following:
IF (weight_loss_rate < desired_rate)
input -= 200 cals
ELSE
input += 50 cals
END
After following this algorithm, your caloric intake will converge to the region [optimal rate - 150, optimal rate + 50]. This is true even accounting for noise in the measurements - that just smears out the -150 and +50 a bit.
The nice thing about bodyweight is that it's a stable monotonic dynamical system. Noise and uncertainty don't hurt you much provided you build robust controls.
Again, my problem is not with speciality diets or finding good habits / regulating eating through macronutrient partitioning. I get it; trust me. But these diets show few benefits beyond "tricking" the person into eating fewer calories, period. There are other variables, but not when it comes to pure weight loss. Thermodynamics cannot be defeated by human biology. Otherwise we could hook up people who are not subject to these laws to treadmills with generators on them, and bam. Free power for the world.
It's not that I was disagreeing with you regarding thermodynamics, just that usually when that point is made the emphasis is on calories in (such as you are making). From what I have seen it seems that many things, including diet can have a strong effect on calories out. That is worth exploring. I just simply disagree with the fact that all diets show few benefits beyond tricking the person into eating fewer calories. How a particular diet makes you feel is an important part of the equation.
If I eat a poor diet and work out, that workout is going to be terrible (even if I ate a lot of calories for example).
