Protein's Hidden Benefit: Stopping Energy Crashes Mid-Workout

According to a 2023 study in the Journal of the International Society of Sports Nutrition (PMID: 37430345), 68% of endurance athletes experience exercise-induced hypoglycemia during training sessions lasting over 90 minutes. But here's what those numbers miss—most of those athletes were consuming carbohydrates alone before training, completely overlooking protein's role in glucose regulation.

I've had marathoners collapse at mile 18, CrossFit athletes hit "the wall" during Murph, and soccer players who couldn't finish a second half. Every time, we traced it back to blood sugar instability. Your body doesn't read studies—it just knows when glucose drops below 70 mg/dL, you're going to feel like garbage.

Quick Facts Box

What Research Actually Shows

Look, the research is one thing, but in the weight room—or on the track—you need practical applications. Here's what matters:

A 2022 randomized crossover study (doi: 10.1136/bmjsem-2022-001423) had 48 cyclists complete 2-hour rides with either carb-only or carb+protein (25g whey) pre-fueling. The protein group maintained blood glucose within 15% of baseline, while the carb-only group dropped 34% by the 90-minute mark. That's the difference between finishing strong and bonking completely.

Dr. Louise Burke's team at the Australian Institute of Sport published work in the International Journal of Sport Nutrition and Exercise Metabolism (2021;31(4):291-301) showing protein stimulates glucagon secretion—that's your body's "raise blood sugar" hormone—while slowing gastric emptying. Translation: you get a steadier glucose release instead of that sugar spike and crash.

Here's a case from last season: I worked with a triathlete who kept hitting energy walls during the run leg. We switched her from gels-only to adding 20g of whey isolate 30 minutes before the bike. Her glucose variability dropped from ±28 mg/dL to ±12 mg/dL. She didn't get faster overnight, but she stopped collapsing at aid stations.

Dosing & Recommendations That Actually Work

I'll admit—five years ago I would've told you protein timing didn't matter much for endurance. But the data since then... well, I was wrong.

For sessions under 90 minutes: 15-20g protein with your pre-workout meal (2-3 hours before). I usually recommend Thorne Research's Whey Protein Isolate—it's NSF Certified for Sport, and their third-party testing actually means something.

For sessions over 90 minutes or high-intensity intervals: 20-30g protein 30-60 minutes before, plus 10-15g per hour during training. A 2024 meta-analysis (PMID: 38523467) pooling 18 studies (n=1,247 total participants) found this protocol reduced hypoglycemia incidents by 47% (95% CI: 38-56%).

Forms that matter: Whey isolate absorbs fastest. Casein or plant proteins work if you're 2+ hours out. Avoid "mass gainers" with 80g of sugar—that's asking for a crash.

One of my weightlifters—a 220-pound strongman competitor—was getting dizzy during event training. We added 25g of NOW Sports Whey Protein Isolate to his pre-training oatmeal. His glucose stayed stable through 2-hour sessions that previously left him needing to sit down between events.

Who Should Be Careful

Honestly, most athletes benefit from this approach, but there are exceptions:

Kidney issues: If you have pre-existing kidney disease, high protein loads can be problematic. I'm not a nephrologist—get clearance first.

Diabetes on insulin: Protein does affect blood sugar, just more slowly. If you're insulin-dependent, you need to monitor and adjust. I always refer these cases to an endocrinologist who understands sports.

Gut sensitivity: Some athletes get GI distress with protein close to training. Start with 10g and work up, or try hydrolyzed whey (though it's pricier).

FAQs

Does the type of protein matter for blood sugar control?
Whey works fastest—30-60 minutes pre-training. Casein and plant proteins need 2+ hours. For during-training sipping, hydrolyzed whey or essential amino acids avoid gut issues.

Can I just eat more carbs instead?
More carbs often mean bigger crashes. Protein modulates the insulin response. A 2023 study (n=89) found carb+protein maintained glucose 42% better than double the carbs alone.

What about intermittent fasting athletes?
If you train fasted, you're relying on liver glycogen. Add 10-15g EAA during training to prevent muscle breakdown without spiking insulin much.

How do I know if I'm having blood sugar crashes?
Shakiness, dizziness, sudden fatigue, irritability mid-training. If you "hit the wall," that's often hypoglycemia. Continuous glucose monitors help but aren't essential.

Bottom Line

• Add 20-30g protein to pre-workout nutrition for sessions >90 minutes—reduces hypoglycemia risk by nearly half
• Whey isolate works fastest; casein or plant proteins need more lead time
• During training, 10-15g protein per hour maintains glucose better than carbs alone
• Monitor response—some athletes need less, some need more. Your body will tell you.

This isn't medical advice—just what I've seen work with hundreds of athletes. If you have health conditions, talk to your doctor.