How Do I Fuel Rides if I’m Pre-Diabetic and Off Sugar?

QUESTION: For a pre-diabetic person (really diabetic since you are or you are not) what are suggested nutrition before/after cycling rides? Considering the person has eliminated sugar including flour, bread, etc., and the person is not taking insulin nor has the desire to do that. I don’t know if you’ve covered this topic before, but I have an interest in how other riders have handled it. Thank you kindly. — RBR reader SC

RBR REPLIES: Pre-diabetes and metabolic syndrome now affect roughly a third of US adults, which means plenty of cyclists deal with it. The conventional cycling-nutrition playbook (carb-load the night before, oatmeal-and-banana breakfast, gels every 45 minutes, rebound carbs after) is built for someone with a normal insulin response. If you’ve taken yourself off sugar and flour to manage blood sugar with diet alone, that playbook doesn’t fit your kitchen. Here’s a framework that might.

A disclaimer up front: we’re not physicians, none of this is medical advice, and you should talk with a doctor, ideally one familiar with low-carb metabolic management, before changing what you eat.

The big idea: fat adaptation

Start with what your body is already doing. When you cut sugar and refined carbs and your blood sugar normalizes, your metabolism slowly retools to burn fat as its primary fuel during low- and moderate-intensity work. Tim Noakes (https://nutritionnetwork.org) calls this being “fat-adapted.” Volek and Phinney’s FASTER study (2016) (https://pubmed.ncbi.nlm.nih.gov/26892521/) showed elite ultra-endurance athletes on low-carb diets oxidizing fat at roughly 2.3 times the rate of their carb-fueled counterparts, doing it without depleting muscle glycogen. A fat-adapted rider has access to a much larger fuel tank and doesn’t need a constant carb drip to keep moving.

Getting there isn’t instant. Most riders feel weak, sluggish, or generally “off” in the first two to six weeks of low-carb riding. That passes. Once you’re through it, the steady-state aerobic ride that used to require a gel or two is something you easily finish on water.

For racing and very hard rides, no carbs are not going to give you the best results. Sugar helps. I don’t avoid carbs if I race or do gravel events. (I also do not have any blood sugar issues.)

Before the ride

For most rides under about two hours at a conversational, zone-2 pace, a fat-adapted rider can go fasted. That’s what I do: a regular 33-mile morning ride, fasted, finishing feeling fine. If a fasted ride leaves you wrecked, you’re not fat-adapted yet. Back off the intensity, give the adaptation a few more weeks, and try again.

If you do want something in the tank (for a longer ride, a harder ride, or just because you’d rather eat) keep it protein-and-fat dominant. A couple of eggs. A spoonful of unsweetened nut butter. Plain Greek yogurt. Half an avocado with salt. None of those will spike your glucose, and all of them carry over into the ride better than a quick-burn carb breakfast.

During the ride

For rides under two hours at moderate effort, water plus electrolytes is plenty.

For longer or harder rides, the on-bike toolkit looks different from the gel and energy drink default. Nut butter packets, hard cheese, jerky, and hard-boiled eggs all work. If you want a structured carb fuel that doesn’t spike glucose meaningfully, the product most associated with this approach is UCAN SuperStarch (https://ucan.co), a slow-release carbohydrate originally developed for kids with glycogen storage disease. The UCAN drink mix gave me stomach troubles when I tried it years ago, but others have had good luck with it. I have not tried their gel, because it wasn’t yet an option when I last looked at the brand.

It’s worth noting, as Dr. Mirkin has written previously on RBR, that contracting muscle pulls glucose out of the bloodstream through a non-insulin pathway during exercise and for roughly 30 minutes afterward. A small amount of carbohydrate during a hard effort is metabolically very different from the same carbohydrate eaten on the couch. Worth knowing, even if you choose not to use it.

Personally, on hard rides where I am afraid I’ll bonk if I ride them fasted, or if I think the ride might go longer than two hours, I like to carry a bottle filled with the endurance drink Spiz (https://spiz.net), which I’ll drink if the ride starts to get hard. I also often carry a That’s It fruit bar (https://thatsitfruit.com) (just two fruits smashed up so there’s also fiber, no added sugar) in a jersey pocket as bonk insurance. Both rarely come out. The point for me is to have a backup plan and not to fuel preemptively.

After the ride

This is where conventional advice goes loudest in the wrong direction for you. The standard “rebound carb window” doesn’t apply when carbs are exactly what you’re managing away from. Your post-ride priorities are protein for muscle repair, fluids, and electrolytes. Eggs, fish, meat, plain Greek yogurt, Skyr (no sugar added), cottage cheese, or other low carb foods all do the job. A few blueberries are fine if you want some sweetness.

Personalize it

The single highest-leverage thing you can do is measure. A glucometer is cheap. An over-the-counter continuous glucose monitor like Stelo (https://www.dexcom.com/en-us/stelo), Lingo (https://www.hellolingo.com), or Levels (https://www.levelshealth.com) runs around $90 for a two-week sensor and tells you exactly how your body responds to specific foods, ride durations, and intensities. Wear one through several rides and you’ll personalize this faster than any article can. You might find that while riding, gels or energy drinks don’t spike your blood sugar that much at all.

Readers, if you’re managing diabetes or pre-diabetes through diet alone and you’ve worked out what fuels your rides, let us know how you’re doing it in the comments.