There is a huge amount of scientific literature (see summaries by Gary taubes, for example) that show that calorie counting is not the whole picture when it comes to health or obesity. It's also definitely not a golden rule.
Not to say it's not a useful diet method. Just that there are a lot of factors that go into "calories out"-- what calories are being used for energy and what are stored as fat. How fast are you burning calories? Hormones are a big part of that. You can see this very clearly in hyper/hypo thyroid patients.
Hormones only can not explain the percentage of overweight people in western countries. 50% of the population does not have hormones fucked up enough to not lose weight.
Also, famine makes you passive, tired and well, less bright. There is a reason why famine prone areas dont produce tech hubs and nobel prize winners.
There are other health problems due to this "extreme diet" but being overweight is not one. So if you want to lose weight do like them and eat less than what your body needs.
You don't see a lot of overweight people in famine prone areas. Calories out - calories in = your weight curve. That's the easy part for losing weight.
Sport does not burn a lot of calories. So it is better to cut on the intake. Which is the hard part: food can be a comfort drug which is easily available. Worse when your entourage is full of overweight people as crab mentality can set-in and they'll try to sabotage your weight loss.