Dr. Robert Atkins. Was he a genius, a quack, both?
I strongly agree with him that the high-carb, low-fat diet promoted by mainstream nutritionists is actually unhealthy and fattening (And IMO is all about maximizing the profits of Agribusiness). In my experience when I eat carb-rich foods I'll feel hungry again in a couple hours, but when I eat a meal with lots of protein and fat I actually feel full for as long as 10 hours afterwards, and therefore I eat less.
On the other hand, he seems to have went off the deep end in his later years into the nutritional supplement woo. Thinking, for example, that high doses of Vitamin B12 cures Autism.