Originally Posted by
Happy Feet
At the same time, if one is adapted to only burning carbs and sugars for energy as with a steady high carb/junk food diet, the body will be less adapted to transforming body fat to energy and the bonk from not eating (when glycogen stores are used up) will be more pronounced.
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This is probably the most important takeaway, assuming you are not shredding your muscle fibers of course.
My personal experience when on junk food for a long time is that it's like shifting gears when the sugar in the blood is depleted; the effort becomes huge. However, if I'm eating sugar free and intermittent fasting, then an endurance ride is basically I'll have energy so long as I have fat or I just get bored (around five hours or 60 miles).
In practice during the summer months I don't bother eating before or during rides, as it just doesn't matter because if you have body fat then you're golden.