Performance Nutrition Is Not Health Nutrition
When it comes to nutrition, hopefully it is becoming more common that it should look different depending on your goals. If you have performance goals, it will look different than someone who has aesthetic goals. You can read more on that here and here.
While the quantity of food will look different for someone training 3-6 hours/day vs someone training ~60min/day, the quality may also look different.
Why? The goals of each individual are different. Someone training 3-6 hours/day is in a higher recovery demand than the latter individual. Someone training 3-6 hours/day to be the best at their sport, such as functional fitness, may not prioritize living to be 100 years old at that point in time. I can guarantee you that an NFL lineman probably does not care about his fasting blood glucose level. Sometimes doing whatever it takes to train and recover to be the best at their craft means eating lower quality food sources just to get calories in so the recovery process can start quicker.
Have you ever done multiple training sessions in a day and grabbed some raw broccoli to munch on immediately post workout to refuel? Heck no, because 1) there's hardly any calories in that, and 2) it takes way longer to digest.
When an athlete is training multiple hours a day, multiple times per day, the caloric expenditure is going to be through the roof. Calories and carbohydrates need to be at an adequate amount not only to fuel that training but to recover from the nervous system demands of it. It is pretty common to see athletes eat lower quality food sources such as gummy candy, breads, pizza, etc. just to get calories in---but NOTE, that may not be OPTIMAL for all athletes. At that point, recovery is most important to them, not their health blood markers, therefore the importance of food quality and micronutrients sometimes takes second place on the priority list.
An athlete that does not have a desire to beat their body into the ground and be the best in the world probably cares a little more about their health markers than someone training to be the best. Food quality and getting micronutrient rich foods is going to be higher on the priority list, or at least it should be. The carbohydrate intake of these people will be lower than someone training 6x the amount because their recovery demands are different.
From a health and longevity standpoint, the extremely high amount of carbohydrates that performance athletes need to consume could show effects on insulin, lipid metabolism, glucose tolerance, body adiposity, and is associated with cardiovascular disease risk (Polacow, V. O.). Different priorities come with different actions and different consequences. One person might be fitter than the other, but the other person is likely more healthy from an internal/blood marker perspective.
Just remember that when you are focusing on one thing, something else is going to fall behind on the spectrum. When you focus only on body composition, health is probably not going to be as great as it should be. When focusing solely on performance, health will not be as great as it could be. When focusing mainly on health and longevity, performance is going to take a backseat. If you are a genetic freak, you might have a great body composition as well, but it is not all the way to the end of that spectrum as an extreme.
Know your priorities and make sure your actions align with them.
Polacow, V. O., & Lancha, A. H. (2007, April). [High-carbohydrate diets: Effects on lipid metabolism, body adiposity and its association with physical activity and cardiovascular disease risk]. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/17546237
Hughes, V. A., Fiatarone, M. A., Fielding, R. A., Ferrara, C. M., Elahi, D., & Evans, W. J. (1995, August). Long-term effects of a high-carbohydrate diet and exercise on insulin action in older subjects with impaired glucose tolerance. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/7625352