I don’t know if you would consider bicycling 200-300 miles a week and averaging 19-20 MPH for 65 miles a typical athlete especially with PKU. I have classical PKU and have done bicycle events on both east and west coast. West coasts events are 100 miles of bicycling or more and I usually average 300+ miles that week just because the only transportation I use is a bicycle.
On a 100 mile ride I burn 1700-2500 calories depending on my speed. The one thing I do not do is bring PKU formula with me, but I bike 6AM-3PM. I need to consume calories. I burn so much protein even when I am not doing events that I need to have about 100g of protein from food and 40g from formula. My levels are higher as well. Sometimes my levels are 1000+ and drop when I ride because I burn the protein during the day. This drop and burning of protein makes me sick as it would anyone but I notice it more because of my PKU. I always bring lots of biker food including Power Bars with 9g protein or Cliff Bars also with about 9g of protein.
My diet is not a normal PKU diet because of all the protein I burn during the physical activity. I am vegan. My high protein dinner consists of 300+ grams of baked beans (about 10g of protein) and 2 tofu dogs (20 grams protein total) Lunch is lower usual a Camebrook Fruit Frenzy bar for kids (250 cals and 10 pro) and some fruit (1lbs grapes or apple) I don’t record how much I have because I can feel where my protein is at and I eat more or less based on that. Too low and I can’t sleep or relax. Too high and I can’t think and feel confused. I can’t get blood levels back quick enough to care about sending blood samples.
Just because my levels are 1200 (micro moles per liter) doesn’t mean their are too high. I may need that protein for a bike ride. As I tapper off the bicycling I also reduce my protein intake and I can get my levels down to 700 micro moles per liter.