Yes, Dave Draper talks about it on his website and his book "Brother Iron, Sister Steel". It was a popular way of dieting back in the day of bodybuilding. Chicken, turkey, and other lean meats can be used in place of tuna but its basically a protein sparing modified fast (originally created by Dr Blackburn) or the stillman diet. Anyway, it is very effective for fast fat loss, only problem is long term adherance. Which is why i'm implementing a similar diet now but gradually increasing calories weekly as to turn it into a maintainable diet.
bds has some points about carbs being overrated, and some people can continue making progress w/ no carbs or carb ups. But it is not true that fat is needed in the diet to achieve ketosis. One can readily achieve ketosis just by cutting out carbs, fat does not need to be added. Ketosis can be achieved w/ a very low fat diet, just eat less than 100g carbs (the lower the deeper level of ketosis achieved), and don't overeat protein, presto, ketosis.
I actually find it amusing reading all these posts on this site and many others how people are eating super high fat diets w/ inadequate protein in order to be in deep ketosis, whereas eating protein is much more muscle sparing than ketosis is. Ketosis is irrelevent in the whole scheme of things and doesnt make fat loss any faster, once protein and efa needs are met, it all comes down to calories.