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Nutrition Myths - Fasting

By: TrueSport  July 03, 2021

For young teenagers, diet culture is hard to avoid. Whether they hear about a new fad from friends or read about a new diet trend in a health magazine, there's often pressure to have some kind of stance on food. And while some diet trends like intermittent fasting might be safe and healthy for most adults, that is not the case for children and teen athletes who are developing at a rapid pace. Any diet that puts restrictions on how an athlete eats should be looked at critically, and fasting in particular can be a gateway to destructive eating behaviors.

Here, TrueSport Expert Kristen Ziesmer, a registered dietitian and board-certified specialist in sports dietetics, explains what parents need to know about fasting and young athletes.

Kids don't need restrictions on diet

Eating when hungry is critical for development—not just physical development, but also for athletes being able to understand their bodies and register their own hunger cues rather than relying on a clock to decide when they're "allowed" to eat. And fasting now can have consequences later: A study in 2013 found that any kind of dieting as a child or young adult increased the likelihood of developing an eating disorder in later years. Meal skipping has also been shown to lead to nutritional deficiencies in kids. Even if they're getting enough calories, it's often hard to make up all of the micronutrients that are critical to a young athlete's development. "Kids should be able to eat whenever they're hungry," Ziesmer says. "There's no good reason that a child should be fasting."

Remember that children model parent's behavior

"Often, kids get these ideas about following diets and food trends from their parents," says Ziesmer. "Remember that what works for you isn't necessarily going to be good or healthy for your growing athlete. And remember that your athlete is watching how you eat and hearing how you talk about food and your weight," says Ziesmer. "I see a lot of parents who are doing fasts or a restrictive diet like Whole30 and their children end up doing it as well."

Even if you're not suggesting that your child do a diet alongside of you, they may want to try it to lose weight, or you may be accidentally restricting their intake because you're no longer making breakfast for the whole family, or you're cooking only Whole30-approved options for dinner. If you're on a diet of any kind, ensure that your athletes still have access to the food that they need.

Fasting can be a gateway to an eating disorder or disordered eating patterns

Restricting hours where eating is "allowed" can be an athlete's way of maintaining strict control, says Ziesmer, and that can easily progress into an eating disorder or disordered eating. "Intermittent fasting is basically just a form of calorie restriction, which is not recommended for kids because they are still growing and developing,” Ziesmer explains. “Intermittent fasting can also lead to binge eating later on because your athlete is so hungry. In some cases, it can even lead to more severe disordered eating. It's better to focus on healthier eating practices overall and being active."

Fasting can cause attention issues in school and sport

For most student athletes, intermittent fasting is difficult because athletes can easily have an early morning practice, followed by a full day of school and possibly another practice, activity, or competition after school. That all requires fuel to function, but most intermittent fasting windows skip breakfast and focus on the middle part of the day—the time an athlete is typically in school and unable to eat an entire day's worth of food during a lunch period.

"There is research about kids who skip breakfast, and it shows that they wind up performing worse in school and on tests," Ziesmer says. "Skipping meals can lead to low glucose, which leads to low hormones, which can lead to agitation and irritability."

Adopt a "natural" eating schedule instead

Ideally, the body does get a break for a span of hours in order to rest and digest (this happens while we sleep). While intermittent fasting isn't a good idea or a necessary one for a young adult, if your teen wants to try it, a 12-hour window (i.e, not eating from 7 p.m. to 7 a.m.) won't be detrimental. It allows plenty of time for the body to reset and recover—getting the potential benefits of intermittent fasting—without depriving your athlete of critical calories. But always make sure your athletes can eat before, during, and after practice.


Fad diets, including fasting, are often not appropriate for developing and active young athletes. Learn why not from our expert dietitian.