So the "eat less" claim in this article is again back to the old MD advice, "eat less and move more". Not going to work if you don't look at your macronutrients.
As you say, it appears to be more complex than just watching how much you take in.
"Milk production at a dairy farm was low, so a farmer wrote to the local university to ask for help. A multidisciplinary team of professors was assembled, headed by a theoretical physicist, and two weeks of intensive on-site investigation took place. The scholars then returned to the university, notebooks crammed with data, where the task of writing the report was left to the team leader. Shortly thereafter the physicist returned to the farm, and advised the farmer, “I have the solution, but it only works in the case of spherical cows in a vacuum.”
Human beings aren't black boxes, we are living, breathing organisms, and as complex organisms we can process food differently depending on what it is. For example, cows eat grass, and can survive on a diet of 100% grass, so they must get some calories out of it. Otherwise they wouldn't be able to sustain the energy expenditure necessary to power a ~2000 pound beast, and would die early. Humans, on the other hand, cannot digest cellulose, so it will land in your stomach as indigestible fiber after which you will promptly poop it out. If you were to give a human an all grass diet, he/she would die within weeks.
In a similar vein, a calorie of carbs is not digested the same way as a calorie of protein, which is also not digested in the same way as a calorie of fat. For the studies that you mention, I'm certain that the macronutrient composition made very little difference when it comes to weight loss in the short term, but I am far more skeptical about whether a high carb diet is actually sustainable after your body has adjusted to a lower metabolic rate. Most studies of this type show a bounce back in weight after the initial weight loss. Furthermore, it's not and shouldn't be all about weight loss; if a calorie is just a calorie why don't you just eat 1500 calories of pure sucrose per day? Assuming you were able to stick to it, you'll quickly get fatty liver disease, diabetes, and a ton of visceral fat. The idea that the macronutrient composition is irrelevant as long as calorie restriction is maintained is too simplistic a view, and a dangerous one to spread.
It's anecdotic but as an hobbyist bodybuilder tracking calories everyday I can confirm that my weight follows exactly my caloric input (there can be some latency but it's water retention mostly), in line with the experience of a lot of people like in /r/bodybuilding or /r/ketogains. Playing with macronutrients and insulin is interesting for muscle gain or breakdown prevention and energy and hunger management but not really for pure weight loss.
I agree with your last paragraph, macronutrients are very important for health and body composition, and sure I would recommend a low carb diet for losing weight in the long term, in part because fat and proteins are more dense and keep hunger low
The moment that you accept that macronutrient composition is very important for health and body composition, you acknowledge that in biological system a calorie is not a calorie. If I want to lose weight, I don't want someone to tell me that CICO so I can just eat whatever as long as I stay under x calories, because as you rightfully pointed out some foods are more energy dense than others, cause fewer cravings, and don't spike your blood sugar. With CICO, I can lose weight but get fatty liver disease, or I can lose weight but lose muscle while increasing visceral fat, since fat weighs less than muscle. These are terrible outcomes. People want to lose weight to be healthier and look better; what's the point of losing the weight if your risk factors for metabolic syndrome go up and you still look fat in the mirror?
For the anecdotal evidence you provided, I think it's not as simple as how you've portrayed it, because your body can be in two energy burning modes, glucose burning or fat burning. If you eat more fat while in glucose burning mode (which is what most people are in), it will just get stored as fat and yes you will gain as much weight as the amount of calories you ate. In so called 'fat burning' mode, your body will increase its metabolism to burn off the excess fat. Likewise, if you're in fat burning mode and you eat more carbs, they'll just get stored as fat. This is also anecdotal evidence (sources: https://intensivedietarymanagement.com/who-needs-to-avoid-fa..., https://intensivedietarymanagement.com/smash-the-fat-calorie...), because unfortunately we don't really have good nutritional studies about this.
There's been tons of research on diets. Low-carb high-protein diets certainly do work, but so do several other diets, including some of the traditional "eat less calories" diets (the research I've seen indicates those diets are on par with Atkins and keto in terms of long-term weight loss, and they all work when consistently/correctly applied). Reducing calories below resting metabolic rate demonstrably causes weight loss. It's almost impossible for it not to.
And, there are ways to manipulate insulin response without going to a high-protein/fat low-carb diet. I've been experimenting with intermittent fasting; where I eat mostly freely, but responsibly, for ~8 hours out of the day and fast the other ~16. This has been shown to improve insulin response, in similar ways to low-carb diets.
I've lost about 16 pounds over three months. Every few weeks, I change the diet, to see how my body responds, in terms of energy, weight, etc. And, also because I love food and really like variety (lots of weight loss programs suggest a very regimented diet of the same thing every day for months or years, but that's not for me).
I've found that when my calories are below my MR, I lose weight, no matter what I'm stuffing my face with. I did a couple of weeks of bread and pie and ice cream every day (to the point where I got tired of bread and pie and ice cream), and still lost weight during that time; calories were consistently below my MR. And, I did nothing but proteins, and healthy fats, and greens for a few weeks, too...also lost weight, but not notably more than the "bread and pie and ice cream" weeks.
I've kept logs of my weight and caloric intake for a couple of months, and it's pretty consistent. A couple days after I eat more calories than my MR, my weight either stabilizes or increases. And, a couple days after I return to below-MR, I see the weight dropping again. I will say that I've had better luck with intermittent fasting than with portion control as a means to achieve below-MR caloric intake; so maybe there's something to the insulin response theory since there's evidence fasting helps with that.
There may also be an argument to be made about cravings (sugar+fat can cause cravings; there's decent science on that), and that may lead to problems managing portions and caloric intake. And, there's certainly evidence that protein and fat calories are more satisfying than sugar or simple carb calories. It may very well be easier to lose weight on a high-protein and high-fat diet. But, when I was on the high-protein/high-fat diet, my cravings for fruit were pretty intense, and the weight loss was not measurably better than the other macronutrient mixes I've tried. I didn't find it valuable enough to continue, so I went back to eating rice, bread, and having dessert sometimes.
But, "eat less" still works, and always will. That's not really negotiable. The basic physics of the thing require it to work. It's just that a lot of folks have no idea what "eat less" really entails and don't keep track of what they eat well enough to know they're not actually doing it. When losing weight, you're going to experience hunger sometimes, which is not a thing modern people are accustomed to.
I am active but not for the sake of fitness. The only time my weight really changes is when I am sick.
My physician doesn't know, I don't know, and it is just how it is for me. I've tried to pound calories into me, but I pretty much stay at 172 pounds. Why 172? I have no idea. I can get on the scale and that's usually what it reads, within maybe two pounds.
If I eat less, I stay the same unless I really, really eat less - like go on a binge of illegal substances type of not eating. I dunno?