Well really, not so much a diet as a fundemental change in eating habits. For those who are not aware, there is a growing body of research that shows that almost all mammals when kept to a restricted degree of caloric intake tend to live longer and be healthier. This is not simply starving one's self or just cutting back, it is instead eating foods that have the highest nutritional bang for the buck. Mostly fish and dark/colorful veggies. Only now is the understanding as to why this works the way it does starting to emerge (assuming the line of investigation pans out), however most labratory animals that have lived on diets roughly over 2/3's the average intake tend to live significantly longer.

Has anybody been on such a regimen?

I have been slowly paring back my own daily intake with an eventual goal average of about 1200/day