1 of 20All photos
While they are great for your body (and weight loss), flaxseeds are full of fiber, which could impede your workout efforts by causing gas and/or bloating, says Stella Metsovas, a clinical nutritionist and diet expert in Los Angeles, Calif.
"You definitely want to limit the amount of fiber you take in 2 hours before and after exercising. In addition to flaxseeds, stay away from fiber supplements, bran, and high-fiber breads and opt for a mixture of protein and carbohydrates instead right before your workout."
2 of 20All photos
Think that energy gel is a great way to prep for your workout? Think again! "Unless you are very athletic (engaging in over 90 minutes of cardiovascular training per day), chances are you don't need those gel packs, Metsovas says. "Taking in all that sugar will disrupt insulin levels and lead you to a dietary-binge later on in the day."
3 of 20All photos
Don't get us wrong, we love healthy hummus just as much as you do, but you may want to stay away from it right before a workout.
"Bean-based foods (such as hummus) are high in indigestible carbohydrates that may cause uncomfortable gas and bloating," says Mary Hartley, a registered dietitian in New York City.
4 of 20All photos
While low-fat dairy may be part of a healthy diet, consuming it before a workout could slow you down. "Most athletes I work with have issues consuming dairy 2 hours before and after exercise," Metsovas says. "I'd advise limiting the use of dairy if you feel lethargic, acidic, or experience excessive burping."
5 of 20All photos
Even though most flavored waters are touted as great 'fitness' drinks, many are full of sugar, or worse, artificial sweeteners that could hinder your workout.
"I would not recommend drinking artificially sweetened beverages prior to working out. I'm against artificially sweetened anything. Artificial sweeteners have been shown to disrupt beneficial bacteria in your gut, and optimal digestion and absorption of nutrients begins in a healthy gut," Metsovas says.
High Sodium Foods (Roasted Nuts)
6 of 20All photos
Even though nuts are a great snack (and can help with weight loss) most roasted nuts are also salted, and salty foods can disrupt the delicate fluid-balance required for optimal workouts, Metsovas says.
"I'd avoid [high sodium foods] at all costs. Using a little bit of salt in your meals is OK, but stay away from the following foods: beef jerky, salted and roasted nuts, lunch meats, and processed snack foods like chips (you shouldn't be consuming these foods anyway)."
7 of 20All photos
While bananas are a great pre-workout snack, make sure you grab a ripe one! Unripe fruit isn't a good idea before you work out, as it could cause uncomfortable gas and bloating, Hartley says. Choose a banana that's completely free of any green at the stem. Brown spots on the skin indicate it’s in the ripe stage. At this stage the sugar content will be absorbed easily, otherwise, the unripe banana is in the starch stage and more difficult to digest.
8 of 20All photos
It makes a great healthy snack, but crudite is best served post-workout. Even though they are super nutritious, veggies like broccoli, cauliflower, and peppers are also high in indigestible carbs and can cause bloating or gassiness, Hartley says. Not a good feeling when you're sweating on the treadmill.
Hard Boiled Eggs
9 of 20All photos
Hard-boiled eggs are a great source of lean protein, but they don't provide carbohydrates for energy. Plus, their protein stays in the stomach and takes a long time to digest, which could weigh you down at the gym, Hartley says.
Thai or Mexican food
10 of 20All photos
Spicy foods may help you burn up more calories overall, but they won't help you burn more during your workout if you eat them right beforehand. Even if they are 'healthy' dishes, spicy leftovers (like last night's Mexican or Thai food) can cause heartburn if they backwash into the esophagus, Hartley says.
11 of 20All photos
Stopped by Starbucks on your way to the gym? Leave the muffins, croissants, and scones behind for a better sweat session, Hartley says. "They have too much butter, oil, or shortening to leave the stomach quickly."
In other words, you might feel like one of those weights made its way into your stomach.
12 of 20All photos
Don't be fooled. Many protein bars on the market are no better for you than a candy bar! If your bar has more than 200 calories and too little protein, it could be weighing down your workout, says Rania Batayneh, a certified nutritionist and eating strategist.
"If your bar has less than 10g of protein, it could cause a drop in your blood sugar, leading you to feel more tired during your workout. To stay energized, look for a bar (that's under 200 cals) with a protein to sugar ratio of 1:1."
13 of 20All photos
Need an afternoon pick me up? Skip the whipped coffee drink if its within a few hours of your workout time. While caffeine can improve your workout, the excess sugar and calories won't.
"They pack on the calories, but they won't keep you full. And many [coffee drinks] can contain the equivalent of 20 packs of sugar," Batayneh says.
14 of 20All photos
Most energy drinks are carbonated and full of sugar (or artificial sweeteners), which can cause gas, bloating, and fatigue. Not only are they not very good for you, they aren't very good at keeping you hydrated, which is key for a great workout.
Caffeine can help if you need a pre-workout boost, Batayneh says. "But think high-antioxidant green tea or black tea or even a nonfat latte (you get some protein in) which can provide an energy boost. Pair it with the right protein bar for the perfect balance."
15 of 20All photos
While the right smoothie can be a great pre-workout snack or meal, if you buy one on the go, chances are you may get weighed down by extra sugar and fat. Blending your own fruit smoothie (use real fruit, not juice) with a scoop of protein powder is your best option, Batayneh says.
16 of 20All photos
Gulping a glass of OJ might seem like a good idea before your morning sweat session, but you'll question your decision halfway through spin class, when climbing that hill seems impossible. What gives? You are better off eating the orange instead, Batayneh says. Juice (even 100-percent fresh-squeezed) has a lot of sugar, and no fiber. While it still offers some vitamins, it will go right through your system, causing a blood sugar crash later.
17 of 20All photos
Bodybuilders swear by them, so they must be good for workouts, right? Wrong! Not all, but most pre-made protein shakes contain a lot of processed ingredients, excess sugar (or sweeteners), and dairy products that can cause bloating, gas, and fatigue. Not exactly what we'd call a fitness trifecta.
18 of 20All photos
Sure, they may be low-cal, but besides containing some sugar and salt, rice cakes offer zero nutrition or protein to help you stay full or power through your workout routine.
19 of 20All photos
While it seems like the perfect portable pre-workout snack, trail mix can take a long time to digest and can be gassy for certain people, Hartley says.
20 of 20All photos
Steer clear of foods high in fat (even the good kind of monounsaturated fat) like avocados just before exercise. "Fats are very important and should be consumed at other intervals in the day, just try to limit your fat intake two hours before and after exercise," Metsovas says.
Foods with a lot of fat or fiber can be very difficult and slow to digest, and they remain in the stomach a long time. They also pull blood into the stomach to aid in digestion, which can cause cramping and discomfort.