Adolescent Body Weight and Athletic Performance: A Health-Oriented Approach That Discourages Weight Loss

Introduction

“To climb faster, you need to lose weight,” “Swimmers need a streamlined physique,” “Lighter long-distance runners are faster”—these concepts circulating in adult competitive sports are quietly seeping into the youth sports world, creating serious health risks. Among Taiwanese adolescent athletes, the proportion engaging in dietary restriction due to weight anxiety is no lower than that of the general adolescent population.

Puberty is a golden period for rapid bone density accumulation—approximately 90% of a person’s lifetime bone density is established before age 20. If bone development is compromised during this stage due to insufficient caloric intake, the long-term damage far outweighs any short-term “weight loss benefits.”

Special Needs During Adolescent Growth

Why Weight Loss Should Not Be the Goal?

Relative Energy Deficiency in Sport (RED-S): The Silent Killer of Athletes

Relative Energy Deficiency in Sport (RED-S) refers to a condition in which athletes’ long-term energy intake fails to meet training expenditure and basic physiological needs. This is especially prevalent among adolescent female athletes and was formerly known as the “Female Athlete Triad”:

1. Inadequate energy intake
2. Reduced bone density
3. Menstrual dysfunction

Male adolescents can also be affected by RED-S, with symptoms including stalled training progress, weakened immunity, persistent fatigue, and low mood.

The Right Attitude Toward Weight: Let the Body Grow Naturally

Weight Gain During Puberty Is Normal and Necessary

Girls gain an average of 15–20 kg during puberty (approximately ages 10–16), while boys gain 20–30 kg (approximately ages 12–18). This weight gain includes the normal development of muscle, bone, and internal organs—it is not “excess fat.”

Many parents and coaches instinctively think weight gain needs to be “controlled,” not realizing that this is precisely the physiological foundation for the rapid improvement in training capacity seen in adolescent athletes.

Evaluate by Performance, Not by Weight

Adolescent athletes and coaches are advised to assess status using the following indicators instead:

• Running pace: Is the weekly 5 km pace stable or improving?
• Strength performance: Are squat and deadlift weights progressing?
• Recovery speed: Does post-training fatigue subside normally the next day?
• Energy levels: Is there sufficient energy for daily academics and training?

If these indicators are normal, minor fluctuations in body weight can be virtually ignored.

Communication Guidelines for Coaches and Parents

Behaviors to Avoid

• Publicly discussing any athlete’s weight or body fat percentage during training
• Making comments such as “You’ve gained weight lately” or “You’d run faster if you dropped two kilos” to adolescents
• Making children overly focused on the scale at training sessions or competitions
• Using dietary restriction as part of training discipline

Concepts to Actively Promote

• “Being strong is what makes you run fast, swim far, and climb high”
• “Eat well to train well; train well to compete well”
• Encourage children to establish a consultative relationship with a sports dietitian or nutritionist
• Discuss food positively in terms of its energy-replenishing function, rather than calorie control

Reference for Reasonable Energy Intake

Adolescent athletes require 500–1,000 more calories per day than non-athletes of the same age, depending on training volume:

Note: These are only estimated ranges; individual variation is significant. Individual assessment by a nutritionist with a sports nutrition background is recommended.

Practical Recommendations

1. Regular health check-ups: An annual health assessment including bone density and routine blood work helps detect RED-S early
2. Create a safe communication environment: Let children freely express concerns about their bodies without fear of judgment
3. Introduce sports nutrition education: Many university sports science departments in Taiwan offer adolescent sports nutrition courses or lectures
4. If disordered eating behaviors are noticed: Seek help from a child psychologist or adolescent medicine specialist as early as possible

Conclusion

The primary mission of adolescent athletes is “healthy growth,” with “competitive performance” coming second. When the two conflict, health always takes priority. Helping children develop the correct understanding that “food is fuel for sport, and weight is the result of development” is one of the most important responsibilities every coach and parent has toward adolescent athletes. A strong, energetic body is the most solid foundation for future athletic achievement.

Related Reading

• The Hazards of Weight Control in Adolescents: Research on the Impact of Dietary Restriction on Growth and Development
• Nutrition for Adolescent Athletes: Caloric Deficits, Developmental Needs, and Common Dietary Mistakes
• Nutritional Needs of Adolescent Swimmers: Calories and Trace Elements During the Growth Period
• Adolescent Endurance Training: Growth Plates, Training Volume Limits, and the “Early Specialization Trap”