> Actually, foods with a high glycmic load seem to be what's really bad for the heart http://www.ncbi.nlm.nih.gov/pubmed/19364995

From the referenced study: "associations of harmful factors, including intake of trans–fatty acids and foods with a high glycemic index or load"

You seem to have missed the other half of that statement.

> Doubtful, http://ajcn.nutrition.org/content/early/2010/01/13/ajcn.2009...

From the study you link to:

"Of note, in intervention trials that have shown protective effects of reducing saturated fat, ie, the Veteran Affairs (19), Oslo Diet Heart (20), and Finnish Mental Hospital (21) studies, the calculated P:S ratios ranged from 1.4 to 2.4—values that are much higher than the threshold of 0.49 above which CHD risk has been reported to be reduced (44). Relatively high P:S ratios (1.25–1.5) were also observed in the Anti-Coronary Club Study, an early trial that showed beneficial effects of a lower fat diet (30–32% of total energy) (45). The presumed beneficial effects of diets with reduced saturated fat on CVD risk may therefore be dependent on a significant increase in polyunsaturated fat in the diet. Existing epidemiologic studies and clinical trials support that substituting polyunsaturated fat for saturated fat is more beneficial for CHD risk than exchanging carbohydrates for saturated fat in the diet, as described further elsewhere (46)."

Exactly as I said, favoring unsaturated fat in diets over saturated fats seems to have benefits as far as cardiovascular disease, while replacing fats with carbohydrates leads to poor results.

> Polyunsaturated and monounsaturated oils have to be balanced. Too much omega-6 rich polyunsaturated vegetable oil like from soybean or corn may actually increase risk of heart diseases

Sure. I wasn't trying to lay out every possible dietary guideline, just a few rough ones. And I really mean them as rough, and meant to be broken. I don't believe that we know enough about dietary science at the time to make strong judgements; making drastic dietary changes on the basis of poorly understood science can be a bad idea.

One rough metric for whether a diet is good to eat is whether it a similar diet has been eaten over the past few hundred years by agricultural societies; that gives at least some evidence that it works over a large population for a long period of time. It's not perfect, and modern scientific understanding can help us understand and improve it, but it gives you a good baseline.

I don't really buy the paleo idea that we evolved for the hunter gatherer diet, and then evolution stopped; after all, Europeans evolved white skin as a result of agriculture, so I find it a lot more plausible that our digestive system has likewise adapted to agriculture, though it's too quick for it to have adapted to modern industrial agriculture and food processing.

Given that we've been eating butter, olive oil, and lard for centuries, while corn and soybean oil are inventions of modern agriculture, I tend to favor the former over the latter.

> Seriously, you keep calling LCHF keto a "fad diet" and accuse people who talk about it of "selling books", calling it the "be-all cure" or eating "way too much bacon, pork rinds, and the like". Your underlying tone is really ad hominem, you seem to think all ketoers are stupid, uneducated or in it for a quick buck.

I do think that there's a LCHF/keto fad. I've seen a lot of fad diets over the years, and it has all the trappings of one. I don't think that all ketoers are stupid, uneducated or in it for a quick buck, but I do think that lots of well meaning, smart people can get caught up in fad diets, just like the low-fat fad that was popular for so long (and still has plenty of vestiges in nutrition advice and policy today).

That doesn't mean that that there aren't valid uses for a keto diet. That has been demonstrated in a variety of studies, and a classic example is in epilepsy. What I don't think has been demonstrated is the long-term efficacy of keto diets over normal calorie restricted diets. Keto tends to get results quicker (at the expense of some unpleasant side effects) but the advantage tapers off after a year.

On the other hand, low-fat diets are useful for specific therapeutic purposes as well, such as people having gallbladder problems. We've all seen the damage that over-emphasis on low-fat diets for the general population has done. Look at all the trans-fats people have consumed while avoiding saturated fats; and all the sugars that have been substituted for fats in foods to try to make bland processed food taste better.

From the evidence I've seen, I think that low-carb is likely to be a bit safer than low-fat as it's easier to wind up consuming more calories in carbs when eliminating fat than vice versa, but I do worry that too many people deciding to jump on the low-carb high-fat or low-carb high-protein bandwagon may wind up doing themselves harm; possibly from causes that we already know, and possibly from things that we don't know.

By the way, I think you've mistaken what ad-hominem is. An ad-hominem attack is one in which you attack a person rather than their ideas. That's not really what I've done; I've just been fairly dismissive about the idea. Perhaps I've been unduly dismissive, but having recently been in a thread discussing gluten free diets, I'm feeling a bit uncharitable towards the tendency for people to latch onto a dietary idea that is a very effective treatment for a very specific problem, and decide that it's the solution for everybody and must be evangelized far and wide.