When I talk about fueling the body for sport, I often compare the types of fuel swimmers use to perform. For example, an athlete’s body is like a sports car or a race car. It warms up quickly, gets up to speed swiftly, can go fast, and endure for hours.

Think about it: race car drivers only allow premium fuel in the car to get the most out of the car’s performance. The same mentality should be used for the young athlete. Swimmers want to get the most and best performance from the food supplied to their body.

Premium fuel includes wholesome, nutritious foods that offer calories and nutrients. Foods such as meats and fish, milk and yogurt, fruits, vegetables and whole grains. Plant oils like olive oil, and nuts and seeds. These foods offer high-octane fuel for the athlete, not only providing nutrients for performance, but for recovery and growth, as well.

In stark contrast, there are foods that don’t help or enhance an athlete’s performance. Even though they provide energy (calories), they don’t offer much in terms of nutrients, which keep the body processing the calories that have been consumed. As such, they aren’t ideal as a fuel source for performance.

These low-octane fuel sources may negatively affect performance, impacting the strength, endurance and speed of the athlete. Through the course of a day, a week and a season, young swimmers should aim to eat mostly premium fuel sources, and limit the consumption of low octane foods.

8 Low Octane Foods to Minimize in the Swimmer’s Diet

1. Candy bars

Contrary to the commercials touting a candy bar as an energy source to save the middle of the day, the high sugar content of a candy bar can wreak havoc on an athlete’s blood sugar stability. A blood sugar spike (and subsequent plummet) may leave the swimmer feeling shakey, light-headed, hungry and sweaty. Also, candy bars generally have a higher fat content, which may slow overall digestion, leading the athlete to feel full, sluggish and may cause stomach cramps.

2. Sugary Candy

Pure sugar can boost an athlete’s blood sugar level and help him feel energized, but this feeling only lasts for a short time, especially if other nutrients such as protein or fat aren’t eaten in tandem. Eventually, blood sugar comes down and a reactive low blood sugar (described above) may follow.

3. Soda

Soda, both regular and diet, are filling, and the bubbles can cause gassiness in some athletes.  Regular soda is another high sugar, empty nutrient item.

4. Chips (potato, corn, tortilla)

Who doesn’t like a little bit of crunch with their lunch? In the context of a meal, a handful of chips is fine, but as a snack, chips sport a high fat and salt content and won’t provide the optimal nutrition to get through a grueling practice.

5. Chocolate or candy-coated granola bars

What’s so special about a candy-coating? Sure, it looks good to eat and tastes good, but there is a little surprise on the back of the package. Explore the ingredient list and the nutritional profile of a candy-coated granola bar and you’ll see it is similar to a candy bar.

6. Sweet desserts (donuts, cupcakes, cookies)

The double-whammy: sweet grain-based desserts are not only high in sugar, but in fat and calories, too. These aren’t a deal breaker at the end of a meal, but they aren’t ideal as a fuel source before a workout.

7. Ice cream, frozen dairy-based treats, milkshakes

You get the gist: foods with high sugar and fat content should be reserved for special occasions, eaten in the context of a meal (so other valuable nutrients are consumed as well), and generally avoided as a snack for the athlete in season.

8. French Fries

Who doesn’t love French fries? One fry will get you about 10 calories—mostly from fat—and it’s hard to eat just a handful. Remember, all that fat takes quite a bit of time to digest, so eat them hours before training or competing.

Jill Castle, MS, RDN is a registered dietitian, childhood nutritionist, and youth sports nutrition expert. She is the author of Eat Like a Champion: Performance Nutrition for Your Young Athlete. Learn more about Jill at www.jillcastle.com, her resources for athletes, and check out her free list of 70 Awesome Pre-Workout Snacks for Kids here. Coming soon! Eat Like a Champion class for young athletes and their parents.