I came across the word in this passage of an article on a medical discovery:
Part of the reason that heart disease is so prevalent and intractable is that it often requires massive changes to one’s lifestyle— changes that are not easy to make. Everything from radically altering ones diet to implementing serious exercise routines. And while it’s never too late to start, people often realize the true danger only when it’s too late to make the changes and the damage is done.
This is the definition of radical from OALD:
1 concerning the most basic and important parts of something; thorough and complete
radically altering one's diet. I understand the latter part of the definition thorough and complete when it applies to diet, but what about the former part concerning the most basic and important parts of something? When it involves diet does it mean the three main meals?