It's not the math that does or does not work. It's the psychological and mental effects of the above advice.
If person A feels physically sick and completely unable to function while in a 500 calorie daily deficit that's a very different outcome than person B who barely notices that exact same deficit.
That's what leads to this silly argument over whether the "math works" or not.
I think the rational calorie deficit/surplus calculation needs to always be accompanied with a large amount of sympathy and understanding that the psychological and mental effects of these "simple steps" can vary dramatically.
Actually, the physiological effects outside of weight loss/gain are also different.
> If person A feels physically sick and completely unable to function while in a 500 calorie daily deficit that's a very different outcome than person B who barely notices that exact same deficit.
And its probably a sign of a very different physiological response, not merely a "psychological and mental" one.
Additionally, the metabolic response to overfeeding varies greatly between individuals; some people respond to excess calories with a significant rise in body temperature and heightened energy, while others show no change in body temperature and actually get tired after eating.
I'm not saying that "slow metabolism" is a legitimate reason someone can't get fit. Only that it isn't fair to assume everyone is the same; some people DO have a much harder time losing fat and staying lean.
The best thing you can do right now is sit down and make a meal plan, then go shopping for it, today, right now. Here: chicken , frozen vegetables, water. Cook it all, then eat as much of that to feeling totally full, with your choice of sauce, and you will lose weight. Guaranteed. No exercise required, no limits on how much you can eat.
What you described is a reasonable way to get a starting point, but the math almost never works out the way you described. Instead, you must track your body's response over a week or two to a very repetitive diet, then change one or two variables at a time and repeat the tracking process until you get the desired result.