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.

Yes. Sugar (and all of its downstream phenomena - diabetes, insulin resistance, the ease in which sugar adds calories without satiation signals) is well established to contribute to CVD. Long-chain (animal based) sat fat and trans fat is also well established to contribute to CVD. The high calorie density of fatty foods plays a big role, as does the overall palatability and "eatability" of low fiber, high fat, high sugar, delicious foods, making portion control challenging. That should be uncontroversial at this point.

The jury is unclear on:

- How the chain length of sat fats impact things (medium-chain triglycerides seem to be protective, but the boundary between medium and long is fuzzy)

- How the ratio of the various omega-N (3/6/9) unsat fats impacts health, particularly inflammation

- The whole "seed oil" thing is probably MAHA/conspiracy style false signal at the end of the day, but it hasn't been fully debunked and there are almost certainly facets of truth to it (seed oils are a form of ultra-processed food, and all UPFs are problematic)

Confounders, confounders everywhere. This whole field is just extremely challenging and noisy.