Not evidence, but it makes sense if you think about it. Eggs are nutritious, easy to eat (especially for people whose teeth have fallen off) and quite filling.

The most critical element for survival with any diet - particularly with low calorie intake - is protein. Eggs just happen to be the easiest form factor. Personally when I'm on a weight loss regimen, I take in more canned Wild Pacific Salmon than eggs. Salmon, containing less mercury than many other fish, is a fairly safe bet for frequent consumption.

I'm curious how someone with a constant diet of something like eggs and biscuits for 5+ years fares regarding severe deficiencies in truly necessary vitamins and minerals. I do think the body is a miraculous machine that will successfully adapt to many diets that experts would otherwise claim as being dangerously deficient.