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Under-fueling on the bike can lead to big problems off the bike if it becomes a chronic problem. 

That’s why we’re such huge fans of ensuring every ride is correctly fueled with carbohydrates, electrolytes, and water. We love Enervit’s range of nutrition options since no matter what your eating-on-the-bike style is—easy-to-eat and digest gels, sports drink mix, or bars—there’s something for you. 

But fueling enough can be tricky. Since everyone is different, knowing exactly how much you need to eat and drink is hard. In general, it’s recommended that cyclists take in anywhere from 30 to 90 g of carbohydrates per hour while on the bike. That’s a broad range that depends on the energy cost of the ride beyond the essential risk of glycogen store depletion. Duration and intensity (related to athlete thresholds) are the key factors that affect energy cost and glycogen expenditure. This is why the fatigue risk could even appear after a 60-minute ride. 

So, how can you tell if you’re under-fueling your workouts? There are a few, perhaps unexpected, signs to look out for:

Fatigue off the bike

We all know that bonking—that feeling of all of your energy draining out of your body—while on the bike is a sure sign that you need to take in more calories. But being tired in your day-to-day life is another indicator that you may be chronically under-fueling in and around rides. You may also notice disturbances in sleep, especially after longer or more challenging rides.

Mood swings

That’s right: You may be able to blame your moodiness on a lack of carbs on the bike! We all know what it’s like to feel hangry (that dreaded hunger-induced anger). When you’re chronically under-fueling workouts—or even if you are under-fueled on a single long ride—it’s normal for your mood to feel all over the place. (If you’re unsure you fall into this category, ask your spouse. He or she will likely be more aware of your changes in mood than you are!)

Try Enervit’s Sample Pack

Do you know you need to fuel more but still figure out what you will enjoy eating during sports? Enervit has a sample pack that lets you try different styles of gels.

Constant illness/injury

Suppose you’re constantly dealing with small, nagging injuries—even something as minor as lingering knee pain—or you continuously get colds that linger for weeks. In that case, that’s a sign that your body is struggling. Your immune response gets weaker when you’re not giving your body the fuel to get through a workout and start the repair and recovery process.

Decrease in performance

Suppose your power numbers are stalled out or actually going down. In that case, that can be a simple indicator that you’re not fueling enough. If your muscles don’t have the glycogen they need to perform at their best, they’re simply unable to put out the power they used to. This is often subtle initially, not a steep drop off, so look for a downward trend rather than a huge drop.

Lack of hair and nail growth

Brittle hair or nails or even stalled nail and hair growth can be indicators that you’re missing out on eating enough protein and vitamins A, C, and E. This isn’t a sign that you’re missing carbohydrates on the bike. Still, it could indicate that your post-workout recovery nutrition needs a boost. (We like Enervit’s recovery drink mix for an easy blend of carbs, protein, and branched-chain amino acids to speed muscle repair and their best-tasting protein bars!)

At its most severe and chronic under-fueling on the bike can lead to Relative Energy Deficiency in Sport (RED-S). 

RED-S is becoming more prevalent amongst men and women cyclists, and it indicates a severe long-term under-fueling issue. Suppose you’ve been noticing some of these warning signs for a while. In that case, it may be worth speaking to your doctor or a registered dietitian to ensure you’re working towards a healthy balance in your fuel intake.

Molly Hurford

Molly is the author of Fuel Your Ride, and a Precision Nutrition-certified coach. Her writing has appeared in many leading publications, including Bicycling Magazine and Outside. When she's not writing or coaching, she loves ultra-running and racing on trails, riding bikes, or hiking with her mini-dachshund DW.