Study Reveals What NOT to Eat Before Exercise

Picture this: you’re gearing up for tomorrow’s workout and wondering, “What should I eat today?” Most of us assume loading up on carbs is the golden rule. Carbs are energy, right? Well, buckle up, because a recent systematic review has thrown a wrench into this widely accepted belief. It turns out that when it comes to boosting performance in tomorrow’s gym session, eating extra carbs the day before might not be as crucial as we think.

Let’s break it all down. From the surprising science of glycogen storage to the psychology of eating before a workout, here’s everything you need to know about pre-exercise nutrition, and yes, what NOT to eat before you hit the gym.

But it wasn’t anyone of us from BOXROX who dug through new studies to find out what not to eat before exercise. That would be the work of one Thomas DeLauer. Thomas DeLauer is a celebrity trainer and health author. His YouTube Channel has 3 million subscribers and he has been on the cover of numerous international magazines.

The study in question can be viewed in the link below:

The Effect of Carbohydrate Intake on Strength and Resistance Training Performance: A Systematic Review

The Role of Carbs in Exercise

• Carbohydrates are your body’s primary energy source during high-intensity workouts.
• They’re stored as glycogen in your muscles and liver, fueling activities like lifting weights or sprinting.
• The common assumption: more carbs today = better performance tomorrow.

Carbs Today for Tomorrow’s Workout? Not So Fast

• A review of 19 studies examined how carb consumption before workouts affected performance.
• The results were unexpected: no significant difference was found between those who loaded up on carbs the day before and those who didn’t.
• Why? Your muscles don’t burn through all their glycogen stores as easily as you’d think.

“There’s a very good chance that you’re not depleting all your glycogen during a workout, so adding extra carbs beforehand might just be overkill.”

This means most recreational athletes and gym-goers likely already have enough stored glycogen from their regular diet to perform well, especially for shorter or moderate-intensity workouts.

When Do Extra Carbs Help?

• The exception? High-volume training. Think long-distance running, back-to-back gym sessions, or endurance sports.
• In these cases, your glycogen stores might drop to levels where extra carbs make a noticeable difference.
• It’s like your car: a full tank isn’t necessary for a trip to the store, but for a cross-country drive, you’ll need to fill up.

What About Eating Right Before Exercise?

• 15-30 minutes before a workout: Studies showed slight performance improvements, particularly in exercises like squats.
• But—and here’s the twist—even placebo carbs (like sweetened water labeled as “carbs”) improved performance.

This highlights the psychological impact of believing you’ve fueled up. As one study demonstrated, the simple act of swishing a carb drink around your mouth can trick your brain into unlocking energy stores.

“Sometimes, it’s less about the carbs themselves and more about the signal they send to your brain: ‘We’ve got fuel; let’s go!’”

Calories Trump Carbs

• The review also revealed that total caloric intake mattered more than specific macronutrient breakdowns.
• Groups with higher overall calories performed better, regardless of their carb intake.

What NOT to Eat Before Exercise

If carbs aren’t always essential, what should you avoid?

1. High-Fat Meals

• Fat takes longer to digest, making you feel sluggish.
• Avoid greasy or fried foods before a workout to prevent discomfort.

2. High-Fiber Foods

• Foods like beans, broccoli, or whole grains can lead to bloating or gas, not ideal for burpees or deadlifts.

3. Excess Sugar

• While it provides a quick energy boost, the subsequent sugar crash can leave you feeling drained mid-workout.

4. Alcohol

• Dehydrating and slows recovery. Enough said.

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So, What’s the Ideal Pre-Workout Meal?

Focus on easy-to-digest carbs, a moderate amount of protein, and minimal fat. Examples include:

• A banana with peanut butter.
• Oats with a drizzle of honey.
• A small turkey sandwich on whole-grain bread.

If your workout is hours away, balance your meal with protein and some healthy fats to sustain your energy.

Final Thoughts on Pre-Exercise Nutrition

Here’s the takeaway: stop stressing about carb-loading unless you’re an endurance athlete or preparing for a high-volume session. Instead:

1. Eat enough calories overall.
2. Focus on balanced meals.
3. Trust your glycogen reserves to get you through most workouts.

The science isn’t saying carbs are bad—it’s just showing that for most of us, the timing and context matter more than piling on that extra plate of pasta. And remember, sometimes the biggest boost comes from believing you’re fueled up and ready to crush it.

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