It's just doing the math as other have stated. All the advice is good. I'll try to add some.
For a 3 hour ride at 75 to 80% HR I really don't do much different except replace what I've used.
Know your BMR, What is your height, weight, age, sex. I have a spreadsheet. Then I would pick a macro nutrient ratio, Carbs, Protein, fat and each body will have a different requirement. My body is good with 40, 30, 30. Sparks it too high in Carbs for me. I do increase carbs to 50 or 55 day before a long effort like a metric century or century. I need about 3500 calories a day to maintain my weight at my activity level. I'm carbo sensitive and try to eat foods lower in the glycimex index. That is for me and my body type.
Hydrate, now I only drink water. In the past I have used energy drinks.
I don't know your fitness level. For me at eating 1500 to 1800 cals would be a huge calorie deficit and I would not last too long with out a bonk. That is when your muscles start to be burned for energy and all you stored glycogen is gone. This causes loss of lean body mass. I don't cut when doing a hard effort. I cut calories when the demands are not too great.
If I'm doing a 50 -60 mile easy ride I don't need to eat any different. What kills me is the hard 2 hour efforts where you HR is in the 90% zone a lot. I'll do a few more carbs 50 - 55 % and then crank up the protein to 35% for a few days after.
Do it by math. Learn your body and always test your eating while training not on the day of the event. You will learn what you need to eat from history and logging.
Send me a message and I'll email you my BMR/Macro nutrient spreadsheet.
| current weight: 192.0