It is complex, but we’ve made it so. Hi carb is very common today, exaggeratedly so. I saw a TV add the other day for a 3-layer stacked pizza - where could that ever, ever be justified, even as a “cheat”? But there’s a demand for it and looking around, clearly so.
In terms of the low carb, my experience is people flip-flop between the two in a desperate attempt to undo the effects of poor discipline. I have no medical training (an engineer), but I do wonder whether the typical person’s move to a low-carb diet is effectively an increase in calories. Possibly, but irrespective, I think the two diets represent extremes and aren’t good for the body in the longer term.
I do speak with some personal experience in regard to diets. Up to my early 20’s I had a diet rich in...whatever I wanted. I still remember dinners consisting of a full plate of pasta bolognese, followed by a steak and beans, completed with a sandwich. At my heaviest, I weighed around 102kg (1.82m), until one fine day I decided enough was enough. I altered my diet to the Body-for-life nutrient breakdown (45-45-10 or so) until I was down to about 84kg, after around 8 months. That was about 22 years ago and since then I’ve changed my lifestyle completely. Over time I returned to a less scientific and more “by feel” approach whereby I try and eat balanced meals and avoid things like triple-layered pizzas like the plague! I also exercise regularly, aiming to get to the gym at least 3 times in a bad week. It‘s not easy, but simple choices have a huge amount to do with it. (And becomes more important as we age, unless one really exercises hard: I have a seventy-year old friend that was a competition bodybuilder in his heyday - he trains as hard as I do (or harder!), eats a fair bit, but well and is in fantastic shape).
But overall, the above points are why I think it’s all over-complicated. Just look at the Italians - some years ago, I remember reading in Time magazine that they were the slimmest in Europe...the pasta-eaters?! That was some time ago and one can see that things are changing, particularly amongst the youth (I go quite often), as well as the popping up of fast-food outlets and pizza with fries as a topping! The point about the Italians is that it is a cultural thing to look good/look after oneself and not going overboard. There will be other factors, but in the end, it’s largely about choices.
So in my view, people must cut the cr*p: just eat less and move more. The rest is largely noise.