High-fat high-carb diet certainly is. There is however no conclusive data that high-fat low-carb diet OR low-fat high-carb diet contribute to CVD.
The Mediterranean diet is regarded as quite healthy by many health professionals but, it is also high in carbs and fat. But these are healthy, unprocessed carbs and fats. Whole grains and olive oil.
People going for high fat, low carb / low fat, high carb are usually doing so while also sticking to real foods.
In general we really even barely have enough nutritional knowledge to say if the term 'good fats' even makes much scientific sense, but broad and vague things like "Mediterranean diet" are just total nonsense, from the standpoint of serious nutrition science.
Many people seem to disregard epidemiology, especially when it comes to nutrition (I think because it tends to support unpopular positions). But epidemiology has performed some excellent feats in the name of public health: cholera, smoking, pfao.
It is unfortunate that the large time-lines on these things make more rigor difficult, but I wouldn't throw out the epidemiology.
There are exceptions when there are rare natural experiments (e.g. I forget the country, but the European one where some issue caused all flour for the country to be only whole-wheat, which led to clear nutrient deficiencies due to the phytic acid there) but in general there are way too many confounds, and measurement is far too poor and unreliable (self-report that is not just quantitatively but qualitatively wrong, and you can't track enough people nearly long enough), there is virtually no control whatsoever (diets and available foods shift considerably over just decades), and much of the things being measured lack even face/content validity in the first place (e.g. "fat" is not a valid taxon, and even "saturated vs. unsaturated" is a matter of degree).
We are missing so much of the basics of what are required for a real science here I think it is far more reasonable to view almost all long-term nutritional claims as pseudoscience, unless the effect is clear and massive (e.g. consumption of large amounts of alcohol, or extremely unique / restrictive diets that have strong effects), or so extremely general that it catches a sort of primary factor (too much calories is generally harmful, regardless of the source of those calories).
But even setting that aside, you can't define or study "Mediterranean diet" rigorously even in RCTs, so I don't see how you can think you are going to get much of anything here from epidemiological work that is going to lead to anything practically actionable.
But all that aside, I don't actually follow a Mediterranean diet, and agree that one has to be careful here, because it is not well defined (or, it might be in some circles, but that differs from what the general population might expect).
The only reason I mentioned it was in response to
> The Mediterranean diet is regarded as quite healthy by many health professionals but, it is also high in carbs and fat.
Where I was pointing out that the fats in the Mediterranean diet (by pretty much every measure of what it means to be a Mediterranean diet), are not saturated, and it is usually saturated fats that are considered "bad".
That is, all I was trying to do was clear up the (common!) confusion about fats (they are not all the same).
I also think it is better, rhetorically, to not draw support for the badness of saturated fats / differences of different fats by referencing the Mediterranean diet, since this rather looks like drawing upon narrow / weak science to support something that is in fact much more broadly supported by a larger variety of more careful work.
But yes, it is very important that people recognize there are huge differences here!
Also, the 7 countries study didn't just compare the regions, they also did intra-regional comparisons. Not that I think this particular study is what you should base all your evidence on, but, most others back it up.
The people who run these studies actually know what they are doing. They know the limitations of their methods, and, they have thought about confounding variables. This _always_ comes up in internet debate, like, "ahh, but there are confounding variables so the study must be trash!". It's literally their job to take those confounding variables into account. They don't just grab random people of the street to run these things. And I assure you, they know about the details.
Have to be a little careful with this claim. Dietary saturated fat and cholesterol are problematic either way.
The "well, actually" point on this is that dietary saturated fat drives blood cholesterol levels more strongly than dietary cholesterol. But it is not true that dietary cholesterol has "zero impact," and it is not true that "saturated fat we don't have reliable data that points to it being harmful." High-cholesterol foods are typically high in saturated fat, so these things are kind of intertwined.