The 80/20 rule on nutrition follows The Pareto Principle. The Pareto principle states that for many outcomes, roughly 80% of consequences come from 20% of causes (the "vital few").
"The 80/20 diet approaches healthy eating with a message of moderation—80 percent healthy choices and 20 percent flexibility for less healthy options. Nutrition professionals back this approach, as it’s feasible for all, allows for a variety of foods, and avoids deprivation."
—Chrissy Carroll, RD, MPH
Yesterday was my birthday so we went out to dinner with 2 other couples. We all cut loose and enjoyed ourselves with a few adult beverages, some nice steaks and a couple of delicious desserts. While we broke our routine to enjoy a night out with friends, we allow ourselves that freedom because of the daily habits we have built.
We focus on eating foods that are in their natural form; vegetables, nuts, seeds, meats, fish, and fruits, in this order; eating a full spectrum of them at levels that support exercise but not body fat. If 80% of the time, i.e. 5 or 6 days a week, we follow these habits, we can allow ourselves some freedom on an evening out and not feel bad about it. We are the accumulation of all of our choices, and as long as we are making the right ones most of the time we will be better for it.