'Old' in the sense that low carbohydrate, high fat diets have been known about for a century or more as a way to treat autism, and in the sense that there are studies from the middle of last century which replaced saturated fat in peoples' diets with seed oils which showed no benefit or even increased mortality. Some of these studies were botched or cherry picked their data to support a conclusion that saturated fat is bad for our health, but upon re-analysis have shown no such effect. See for example the Sydney [1] or Minnesota [2] heart studies. The confusing aspect with these studies is that frequently they show a decrease in cholesterol when switching to seed oils, and conclude that seed oils must be healthier than saturated fats, but it turns out that cholesterol levels have very little to do with overall health (sorry for the unsubstantiated claim - I don't have a good reference to hand, but I can look it up if you ask - usual caveats apply: I am not a doctor etc. etc.).

[1] https://www.fasebj.org/doi/abs/10.1096/fasebj.27.1_supplemen...

[2] https://www.bmj.com/content/353/bmj.i1246

If being a vegan/vegetarian is highly correlated with "cares about health," the types of carbs they consume would likely be different, they may be more likely to exercise, and they may be more likely to eat in moderation.

Lots of people say this to me but I've never seen evidence that it's true. In my experience most vegans don't do it for health reasons.

That being said I do agree that there are huge differences in types of carbs consumed....but that only goes to say that the problem isn't simply 'carbs', it's processed sugars.

I have never seen a vegan who is what I would consider "fit" - and my standard is not necessarily an elite athlete, but, let's say, "able to handle themselves in a bar fight". Frankly a lot of them look rather sickly.

I have however met a lot of people who are Paleo or Carnivore who are in incredible shape.

I'm inclined to believe that at least some of this is cultural - Paleo/Carnivore folks tend to be more strict and disciplined about their fitness anyway, and do different workouts - and some of it is indeed due to diet.

It is tempting to think that your diet is what makes you fit, but that's just an excuse. I'm fit because I exercise intensely every day. Whether I'm eating beans or steak doesn't change that.

I've only heard this idea from people who aren't in shape obsessing over all the details of the body except for the one that matters: having the discipline to exercise.

It's like debating whether you should have celery or its close cousin, rhubarb, while skipping your daily run.

Sorry this just made me lol, lookup "gamechangers" and watch the trailer.

I’ll pass, thanks. I have enough evidence, anecdotal and from my physician and from experience, that a plant-only diet would be extremely unhealthy for me. I’ll stick to my steaks.

neat. good argument. anecdotal evidence is not evidence btw.