You want to eat less than 1/3 of the calories you ingest, Go paleo!

"A provisional conclusion, at least for Canada, is that a
healthy diet would contain less than one-third of energy
in the form of ultra-processed products. This could be
achieved only if diets are based primarily on meals and
dishes prepared with minimally processed foods and
processed culinary ingredients."
Impressive study, I would have said 1/2 in a quizz on the subject!
http://journals.cambridge.org/download.php?file=%2FPHN%2FPHN16_12%2FS1368980012005009a.pdf&code=238b3f01ec962adfe5fb4dfe7e2a40f0