Roger Wolfson says that when people talk about fitness, they mostly talk about athletic ability, gym schedules, strength progression, amount of reps, bench press limits, and all those physical attributes associated with what a fit person can do.
However, all that physical activity and capability only make up a minority of the bigger fitness picture. Roger Wolfson mentions that it may (or may not) come as a surprise to so many people that the biggest part of fitness has very little to do with how heavy one can squat or perform pull-ups. It has mostly to do with what one has for breakfast, lunch, and dinner.
That's right, the biggest part of fitness is nutrition.
In fact, Roger Wolfson argues that nutrition makes up around 80% of a healthy and fit lifestyle. If people struggle to get their desired fitness results, it's probably because they're failing in the nutrition department. Whether it's too much sodium or sugar, or insufficient amounts of protein or maybe even water, not adhering to scientifically-backed proper nutrition will almost always keep people from reaching their fitness goals.
And Roger Wolfson firmly believes in the adage that absolutely no one can exercise their way out of a bad diet. With discipline, knowledge, and commitment to proper nutrition. However, people can do wonders with their bodies.