When did you have surgery?
You may want to check with your dietician and hire a sports medicine dietician. Trust the professionals over my two cents 😉
What works for me, may not work for you. I carb load (seven days) and do a pre race and taper. I eat low glycemic carbohydrates. Sweet potatoes, fruits, veggies, oatmeal, whole wheat with my protein. Hydration NUUN tabs/electrolytes added to my water in my hydration vest. I add powdered carbs to my water for calories. I run fasted race day. (I don’t eat products with sugar - example running gels/Gatorade)
these links will give you an idea of how athletes fuel.
https://www.foodcoach.me/eat-runningbiking-weight-loss-surgery/
https://keepmovingweekly.com/2015/06/11/nutrition-for-the-bariatric-athlete-endurance-events/
Running taper:
https://www.teamhotshot.com/blog/tips-taper-race-day/
https://www.runnersworld.com/training/a20072822/marathon-taper/
runners stomach
https://www.bucketlisttummy.com/5-nutrition-tips-to-help-runners-stomach/