79: Does Steady Blood Sugar Mean Better Fueling? CGMs, Sports Gels, and Carbs Per Hour
9 min
Have you ever looked at your blood sugar during a long run and wondered if those spikes and dips mean you're fueling incorrectly? What if that perfectly steady glucose line isn't actually telling you what you think it is? In this Mid-Season Fuel episode of the Endurance Eats Podcast, I'm answering a question from a marathon runner and diabetes dietitian who experimented with two different sports fuels while wearing a continuous glucose monitor (CGM). One fuel, a slow-release cornstarch gel, kept her blood sugar steady around 130–140 mg/dL. The other, a traditional maltodextrin and fructose gel, created much bigger fluctuations, ranging from approximately 70–140 mg/dL. But here's the interesting part: Her energy felt fine with both.So does steadier blood sugar actually mean better endurance fueling? We're breaking down what your CGM can and can't tell you during exercise, why glucose and fructose combinations matter for performance, and whether you still need 60–90+ grams of carbohydrates per hour during long workouts. I'm also answering her follow-up question about digestive issues after long runs, including why certain sports fuels might leave you feeling gassy hours after your workout. Resources MentionedUCAN: Slow-release cornstarch-based sports fuelCarbs Fuel: Maltodextrin and fructose-based sports fuel Barney DE, et al. Exogenous carbohydrate oxidation is higher when consumingglucose + fructose compared with glucose alone during endurance exercise regardless of energy status. The Journal of Nutrition. 2026. https://pubmed.ncbi.nlm.nih.gov/42134413/- Ravikanti S, et al. 13C-labelled glucose-fructose show greater exogenous and whole-body CHO oxidation and lower O2 cost of running at 120 versus 60 and 90 g/h in elite male marathoners. Journal of Applied Physiology. 2025. https://pubmed.ncbi.nlm.nih.gov/41191077/- Morton JP, et al. From metabolism to medals: contemporary perspectives and revisiting carbohydrate guidelines for fueling endurance athletes during exe...