A common misconception many young women and girls hear is that in order to be a better runner, you need to be leaner. If your athlete is training hard, in football, running, gymnastics, swimming, or anything in between, there is a good chance they are underestimating how much fuel their body may need. 

This article will discuss why nutrition is crucial for female athletes and how it can impact performance.

Two jobs for the growing body 

Most nutrition information is written for adults whose bodies have already finished growing, but very little is written for young athletes, about young athletes. As a teen, your bones, muscles, heart, and overall body structure are still developing, but as an athlete, you also need time and energy to recover from training. This is a significant amount of energy demand occurring in the background, compounded by even more energy demand [1,2].

It’s frequently recommended that people should eat until full. This may sometimes work for adults, but can leave young athletes under-fuelled as appetite may not always keep pace with the energy expenditure of training volume and adolescent growth [2].

Why under-eating isn’t as simple as just ‘not eating’

To many, the popular conception of under-fuelling looks like skipping meals entirely. In actuality, it's often much sneakier than that. Maybe your teen opts for a smaller breakfast so they don't feel sick during training; perhaps some toast with jam instead of lunch; maybe the post-training snack gets skipped because they're not that hungry. It may not seem like a lot, but this difference between how much energy the body takes in and how much it uses, sometimes called low energy availability [3], is one of the most common yet often overlooked issues among young athletes, especially girls.

An overlooked consequence of underfueling in female athletes

When the body consistently doesn't get enough energy to support both training and normal bodily functions, it starts prioritising survival, and for girls, this often leads to an irregular, or sometimes complete loss of a menstrual cycle. The brain switches off the hormonal signals that regulate the menstrual cycle to conserve energy, a condition called hypothalamic amenorrhea [3], which can cause periods to become irregular or stop altogether [4].

It may be easy to think of a missed period as just an inconvenience, or maybe even a relief. But it's actually a warning sign from the body telling you that it doesn't have enough energy to do everything it's being asked to do. Left unaddressed, this can affect bone density, growth, and long-term hormonal health. Sports medicine defines this as part of a broader condition called Relative Energy Deficiency in Sport (RED-S), in which under-fuelling affects other factors, including the immune system, mood, and injury risk [3,4].

The important thing to know is that this is preventable and, in most cases, reversible. And the fix is almost always the same: eating enough, consistently [3]. The goal is not to eat to the point of feeling sick every meal. It's about consistency across the day. This can look like: 

• Not skipping or having snack-like breakfasts

• Not leaving huge gaps between meals when you're training (or not training) 

• Treating pre- and post-training food as a mandatory part of training

• Letting yourself eat when you're hungry (even if it's more than you think you need)

Final thoughts 

Under-fuelling doesn't just risk long-term health; it risks affecting performance right now. Athletes with low energy availability often experience slower recovery, more injuries, disrupted sleep, mood changes, and greater difficulty improving in their training despite training hard [3,4]. Being a young female athlete means your body is working extra hard as it grows, runs a marathon, develops, and recovers from training, all at once. A missed period isn't something to just accept as part of being ‘serious’ about sport, and certainly is not a relief. It's a sign worth taking seriously and discussing with a parent, coach, doctor, or registered dietitian/nutritionist.

Eating more isn't the enemy of hindered performance. For young athletes, it's most often the missing piece.

Practical tips 

• Don't skip breakfast, even on busy mornings

• Eat something within an hour after training

• Notice if periods become irregular, lighter, or stop altogether

• Treat hunger as useful information, not something to shrug off

• Talk to a parent, coach, or health professional if something feels off; you don't have to figure it out alone

Food is not a reward for training or something to be earned back afterwards. It's what makes the training possible, and better, in the first place.

To learn more, read more of our resources, book a free conversation with a nutritionist, or explore the products Youth Sport Nutrition create for youth athletes, such as Supergreens, Oat Energy Bars, Multivitamin Gummies, or YSN Food Powders.

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Disclaimer: This article is intended to provide general information about nutrition for youth athletes and is not meant to replace professional dietary advice or individual nutritional counselling. Every child's nutritional needs can vary due to factors such as age, size, physical activity level, and medical conditions. We strongly recommend consulting with a registered dietitian or a healthcare provider before making changes to your child's diet, such as adding food powders. YSN and the author of this article do not take responsibility for any possible consequences from any treatment, procedure, dietary modification, action, or application of medication which results from reading or following the information contained in this article.

References

[1] Desbrow B. Youth athlete development and nutrition. Sports Medicine. 2021;51:1–16. https://doi.org/10.1007/s40279-021-01534-6

[2] Noll M, de Mendonça CR, Rosa LPS, et al. Determinants of eating patterns and nutrient intake among adolescent athletes: a systematic review. Nutrition Journal. 2017;16:46. https://doi.org/10.1186/s12937-017-0267-0

[3] Mountjoy M, Sundgot-Borgen J, Burke L, et al. International Olympic Committee consensus statement on Relative Energy Deficiency in Sport (RED-S). British Journal of Sports Medicine. 2018;52(11):687–697. https://doi.org/10.1136/bjsports-2018-099193

[4] Gordon CM, Ackerman KE, Berga SL, et al. Functional Hypothalamic Amenorrhea: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism. 2017;102(5):1413–1439. https://doi.org/10.1210/jc.2017-00131