Greasy Fast Food
Greasy fast food like burgers and fries might satisfy your cravings, but they can sabotage your workout before you even start. Foods high in saturated fat take longer to digest, which means your body will be using precious energy to process your meal instead of fueling your muscles. Studies from the American Journal of Clinical Nutrition show that heavy, fatty foods slow down gastric emptying, causing sluggishness and even nausea during exercise. Athletes who ate high-fat meals before training reported feeling less energetic and more bloated, according to a 2024 sports nutrition survey. This isn’t just a myth—digesting fat draws blood away from your muscles and straight to your stomach. That’s the last thing you want when you need oxygen-rich blood for performance. So, even if you’re tempted by a quick drive-thru run, it’s best to skip it before hitting the gym.
Sugary Breakfast Cereals
Sugary breakfast cereals are a staple in many homes, but eating them before a workout can actually leave you feeling tired rather than energized. Research from Harvard Health in 2023 found that high-glycemic cereals cause a spike in blood sugar followed by a rapid crash, which leads to fatigue and decreased endurance. These cereals often lack the fiber and protein needed to sustain energy levels during exercise. Many people mistakenly believe the quick sugar rush will give them a boost, but science says otherwise. Regularly eating sugary cereals before exercise has been linked to poorer performance in endurance athletes. Instead, opt for complex carbs with some protein, as these provide a slow and steady release of energy, according to the International Society of Sports Nutrition. That way, you’ll avoid the dreaded sugar crash halfway through your session.
Carbonated Soft Drinks
Reaching for a soda before a workout might seem harmless, but carbonation can create problems you might not expect. A study published in Nutrients in 2024 showed that carbonated beverages increase bloating and gastrointestinal discomfort during physical activity. The high sugar content in soft drinks also causes a spike in blood glucose, followed by a crash, leaving you drained. Even sugar-free options can cause bloating due to carbonation and artificial sweeteners. Many athletes report increased burping and stomach pain when consuming sodas before exercise. This can distract you and prevent you from pushing yourself to your limits. It’s easy to see why experts recommend sticking with still water or electrolyte drinks instead.
High-Fiber Vegetables
While vegetables like broccoli, cauliflower, and Brussels sprouts are great for your health, eating them right before a workout can cause unexpected trouble. According to the Mayo Clinic, high-fiber foods can lead to gas, bloating, and stomach cramps, especially when consumed in the hour or two before exercise. Fiber slows digestion, which is normally a good thing, but not when you’re about to get moving. In 2023, sports nutritionists warned that fiber-heavy pre-workout meals were a leading cause of discomfort among athletes. You might think you’re making a healthy choice, but timing matters just as much as content. Save the veggies for after your workout to avoid any surprises mid-squat or sprint.
Protein Bars with Sugar Alcohols
Protein bars seem like the perfect pre-workout snack, but many are loaded with sugar alcohols like sorbitol or erythritol. Research in the Journal of the International Society of Sports Nutrition (2023) found that these sweeteners can cause bloating, gas, and even diarrhea for some people, especially when consumed before intense activity. Athletes in the study who ate bars with sugar alcohols reported more stomach issues and less focus during their workouts. Sugar alcohols are harder to digest and can pull water into the gut, causing discomfort. Even if the bar is marketed as “low sugar” or “healthy,” check the label for these ingredients. A simple banana or a small piece of whole grain toast is often a safer bet before hitting the gym.
Energy Drinks
Energy drinks promise a boost, but their high caffeine and sugar content can backfire, especially before exercise. Clinical trials published in Sports Medicine (2024) highlight that too much caffeine increases heart rate and blood pressure, which can lead to jitteriness or even heart palpitations during workouts. The sugar in these drinks also produces a rapid energy spike followed by a crash, leaving you more tired than before. Over 30% of gym-goers surveyed by the National Institutes of Health in 2024 reported feeling anxious or experiencing stomach upset after energy drinks. While a little caffeine might be okay for some, large doses are risky, particularly if you’re sensitive or have underlying health issues. Water or a light snack will power you through your workout with none of the side effects.
Spicy Foods
Spicy foods like hot wings or chili can cause heartburn, indigestion, and stomach cramps when eaten before exercise. According to a 2023 article in the journal Gastroenterology, spicy foods stimulate acid production in the stomach, which increases the risk of reflux and discomfort during movement. Many people experience a burning sensation or nausea when combining spicy meals with physical activity. Even moderate amounts of spice have been shown to slow gastric emptying, making you feel heavy and sluggish. Athletes in recent studies reported their workouts suffered if they ate spicy foods within two hours of training. If you want to avoid an upset stomach or embarrassing dashes to the restroom, save the spice for after your workout.
Dairy Products
Milk, yogurt, and cheese are often considered healthy, but consuming them right before exercise can be a mistake for many people. Research from the Academy of Nutrition and Dietetics (2024) confirms that lactose, the natural sugar in dairy, can cause bloating, cramping, and diarrhea in those who are lactose intolerant or sensitive. Even those without intolerance may experience some discomfort, as dairy is relatively slow to digest. Athletes surveyed in 2023 reported that dairy products before a workout left them feeling sluggish and gassy. The last thing you want is a stomachache when you’re about to push your body. If you need a pre-workout snack, consider lactose-free options or stick to easily digestible carbs and a bit of protein.
Pastries and Doughnuts
Pastries and doughnuts may taste amazing, but they’re a poor choice before a workout. These treats are loaded with refined sugar and unhealthy fats, which provide a quick burst of energy that fades fast. Studies from the American College of Sports Medicine (2023) show that consuming high-sugar, high-fat foods before exercise leads to an energy crash and poor performance in both endurance and strength activities. On top of that, the fat in pastries slows digestion, leaving you feeling heavy. It’s tempting to grab a sweet treat with your coffee, but your body will thank you for choosing something more balanced. If you want to perform your best, ditch the doughnut and go for a piece of fruit instead.
Processed Meats
Processed meats like sausage, bacon, and deli slices may be popular for a quick snack, but they’re not ideal before exercise. These meats are high in sodium and saturated fat, as confirmed by the World Health Organization and recent research in 2024. Eating processed meats before a workout can lead to dehydration and sluggishness, with many athletes reporting increased thirst and fatigue. The added nitrates and preservatives also contribute to digestive discomfort for some people. While protein is important, the type and timing matter. Lean proteins like chicken or turkey are better options if you need something more filling before you hit the gym.
