Are you talking about ketosis? I've read about it during the 90s when I was still a healthnut. Apparently it was discovered by scientists who studied the dietary habits of eskimos. They were puzzled by how eskimos remain lean by consuming whale meat and blubber for extended periods. It turns out the body will lose weight if you eliminate carbohydrates from your diet.
Stars like whoopi goldberg and oprah often used it in preparation for gala events. They would have steak for breakfast, bacon for lunch etc.. Apparently it is a very fast acting and effective way of losing weight.
It fell out of favour with doctors because it was damn unhealthy in the long run.