As a gym rat and bicyclist i was having health issues. No drugs or alcohol. Lots of supplements.

I went oxalate free on a zero carb diet for several years and it fixed my auto immune disorder. I lost 30 pounds of muscle in the process because of a loss in appetite. I slowly readded foods into my diet. Turned out that I couldn't handle salicylates in large amounts. It's in most plants as well. 3% of the population shares my intolerance. We can't eat spices or herbs.

All humans have individual variances in our ability to process plant toxins. There's a reason why some people are more prone to kidney stones than others. It doesn't mean someone is unhealthy.

"A pound or two each week"

Thats your problem right there. The next step up from peanut butter, in terms of calories (particularly fats) per kg is actual butter or lard. Its about 50% fat.

I imagine the rest is second hand regurgitation of info they dont really understand.