Researchers studied 60 young elite Nordic skiers (30 female, 30 male) over 24 weeks to understand how their eating habits changed as they prepared for competition season. They found that while skiers increased their food intake by 25%, their training volume jumped by 41-83%. This mismatch suggests many skiers aren’t eating enough to match their intense workouts, which can harm bone health, metabolism, and overall performance. The study identifies new warning signs that doctors and coaches can use to catch when athletes aren’t fueling their bodies properly.
The Quick Take
- What they studied: Whether young elite Nordic skiers eat enough food to match their training demands, especially during the preparation period before competition season
- Who participated: 60 young elite Norwegian Nordic skiers (30 women and 30 men) who train at the highest levels of the sport
- Key finding: Athletes increased their food intake by 25% and carbohydrates by 14.5%, but their training volume increased by 41-83%. This gap means many skiers are likely not eating enough to support their intense workouts, which can negatively affect bone strength, metabolism, and performance.
- What it means for you: If you’re a young athlete in endurance sports, eating enough is just as important as training hard. Undereating relative to your training can weaken bones and slow your metabolism. This research suggests athletes and coaches should pay attention to the balance between food intake and training volume. However, these findings apply specifically to elite Nordic skiers and may not apply to all athletes or fitness levels.
The Research Details
Researchers followed 60 elite Nordic skiers for 24 weeks (about 6 months) as they transitioned from their competitive season into their preparation period for the next season. The study was controlled, meaning researchers carefully tracked and measured specific variables throughout. Participants recorded what they ate daily, focusing on carbohydrates, protein, and calcium intake. Researchers also measured their training hours each week and collected blood samples to check vitamin D levels and bone health markers. They used special scans to measure bone density, muscle mass, and body fat, including a specific type of fat called visceral fat that surrounds organs.
This research approach is important because it captures real-world changes during a critical training period. Rather than just looking at one moment in time, the 24-week timeline shows how athletes’ eating and training patterns evolve. By measuring multiple health markers—not just weight or calories—researchers could identify early warning signs of undereating that might not show up immediately but could cause problems later. This comprehensive approach helps identify which measurements are most useful for catching athletes who aren’t eating enough.
This study has several strengths: it’s a controlled trial with a decent sample size of 60 athletes, it tracks multiple health markers over 6 months, and it focuses on a specific, well-defined group (elite Nordic skiers). The study was published in a respected sports nutrition journal. However, the study only included Norwegian skiers, so results may not apply to all populations. The paper doesn’t specify whether athletes were randomly assigned to different groups or how the study controlled for other factors that might affect results. The relatively small sample size means findings should be confirmed with larger studies before making broad recommendations.
What the Results Show
The main finding was a significant mismatch between how much athletes increased their food intake and how much their training increased. Energy intake (total calories) went up by 25%, and carbohydrate intake increased by 14.5%. However, training volume jumped much higher: 41% for female athletes and 83% for male athletes. This gap suggests that despite eating more, the athletes still weren’t consuming enough calories and carbohydrates to fully support their increased training demands.
Researchers found that athletes with higher muscle mass, stronger bones, and higher resting metabolic rates (the calories your body burns at rest) had fewer signs of undereating. Interestingly, athletes with more visceral fat (the unhealthy fat around organs) showed better bone health markers and metabolism, suggesting that some body fat may be protective when training intensely.
The study identified several promising warning signs of undereating: bone density, bone turnover markers (which show how quickly bones are breaking down and rebuilding), resting metabolic rate, and muscle mass. These measurements appear more useful than just looking at weight or body fat percentage for identifying athletes who aren’t eating enough.
Additional findings showed that muscle mass emerged as the strongest predictor of overall health across multiple measures related to undereating. Athletes with more muscle mass tended to have better bone health, metabolism, and fewer undereating symptoms. Heart rate was also correlated with energy intake, suggesting that undereating may affect cardiovascular function. Vitamin D levels and bone markers showed relationships with both energy intake and training volume, indicating that bone health is particularly vulnerable when athletes don’t eat enough for their training.
This research builds on existing knowledge that endurance athletes, particularly those in sports emphasizing leanness, are at risk for undereating relative to their training demands. Previous research has identified this problem in distance runners, gymnasts, and figure skaters. This study is novel because it focuses specifically on Nordic skiers and identifies new, measurable warning signs (bone markers, visceral fat patterns, metabolic rate changes) that could help catch undereating earlier than traditional methods. The findings support previous research showing that undereating can harm bone health and metabolism, but provide more specific guidance on what to measure.
The study only included elite Norwegian Nordic skiers, so results may not apply to recreational athletes, other sports, or different populations. The study doesn’t clearly explain how athletes were selected or whether they were randomly assigned to groups, which could affect how reliable the results are. The 24-week study period captures one specific training phase and may not represent other times of year. The study measured many variables but didn’t always explain which ones were most important or how they interact. Finally, while the study shows correlations (relationships between variables), it doesn’t prove that undereating directly causes the health changes observed—other factors could be involved.
The Bottom Line
For elite endurance athletes: Work with a sports nutritionist to ensure your food intake, especially carbohydrates, increases when your training volume increases. Don’t assume that eating 25% more is enough if your training increases by 40-80%. Monitor your energy levels, recovery, and performance as signs you may need more food. For coaches and medical staff: Consider tracking bone health markers, resting metabolic rate, and muscle mass as early warning signs of undereating, rather than relying only on weight or body fat percentage. These recommendations have moderate confidence because they’re based on one study of a specific population. Larger studies across different sports and populations would increase confidence.
This research is most relevant to: elite endurance athletes (especially Nordic skiers, distance runners, and similar sports), coaches of young athletes, sports nutritionists, and sports medicine doctors. Young female athletes may be at particularly high risk since the study found they increased training by 41% while only increasing food intake by 25%. Athletes who focus heavily on maintaining low body weight or low body fat should pay special attention. This research may be less relevant to recreational athletes, strength athletes, or team sport athletes, whose training demands and nutritional needs differ significantly.
Changes in bone health and metabolism from undereating develop gradually over weeks to months, not days. Athletes might notice performance decreases, fatigue, or difficulty recovering within 2-4 weeks of undereating. Bone density changes typically take 3-6 months to develop. Therefore, if you increase your training significantly, you should adjust your eating immediately—don’t wait to see if problems develop. Benefits from eating enough to match your training (improved recovery, better performance, stronger bones) may appear within 4-8 weeks but take several months to fully develop.
Want to Apply This Research?
- Track the ratio of training volume (hours per week) to carbohydrate intake (grams per day). Aim for at least 6-10 grams of carbohydrates per kilogram of body weight per day when training intensely. For example, a 60kg athlete doing 10 hours of training per week should aim for 360-600 grams of carbs daily. Log this weekly to ensure the ratio stays balanced.
- When you increase your training volume by more than 20%, set a reminder to increase your food intake proportionally. Use the app to plan meals and snacks that add carbohydrates and calories. For every 10% increase in training hours, aim to increase daily calorie intake by at least 10-15%. Create a simple meal plan in the app that scales with your training schedule.
- Monthly, track three key indicators: (1) how you feel during and after training (energy levels, recovery speed), (2) your resting heart rate (should stay stable or decrease with good nutrition), and (3) your body composition (muscle mass should stay stable or increase, not decrease). If you notice declining energy, slower recovery, or dropping muscle mass despite increased training, increase food intake immediately and consult a sports nutritionist. Use the app to set monthly check-ins to review these three metrics.
This research applies specifically to elite young Nordic skiers and may not apply to all athletes or fitness levels. The findings show correlations between eating patterns and health markers but do not prove direct cause-and-effect relationships. If you are an athlete concerned about your nutrition or experiencing symptoms like fatigue, poor recovery, or stress fractures, consult with a sports medicine doctor or registered sports nutritionist before making significant changes to your diet. This information is for educational purposes and should not replace professional medical or nutritional advice. Individuals with eating disorders or a history of disordered eating should seek professional help before implementing any dietary changes.