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AUTHORS: Kathryn Adel, MS, RD, CSSD, LD and Janet Carter, MS, RD, LDN, CLS, CPT

Insufficient caloric intake can have serious consequences on the health of triathletes (both men and women) including an increased risk of injuries and infections, a decrease in bone mineral density and subsequently an increased risk of stress fractures, micronutrient deficiencies such as iron and calcium and decreased sports performance. It should be noted that the prevalence of eating disorders is higher among athletes than non-athletes and has been on the rise for the past two decades.

The absence of menstruation is a common condition among women athletes but is often ignored and considered to be a normal result of intensive training. It is, however, often caused by an insufficient energy intake that can have serious health consequences. The female athlete triad is first defined by three criteria: an insufficient energy intake, a decrease in bone mineral density, and the absence of menstruation for 3 months or more. On the other hand, it is not only female athletes who are affected. In fact, insufficient caloric intake can increase the risk of fractures and affect the hormones (a decrease in testosterone level) in male athletes as well. This is why the Relative Energy Deficiency in Sports (RED-S) is a new terminology that encompasses the female athlete triad as well as the recognition of this problem in male athletes.

A study of 59 elite athletes (16 of whom participated in the Rio Olympics) revealed that athletes with RED-S have a 4.5 times higher risk of developing a stress fracture. Even a caloric deficit of only 300 calories a day can have a big impact on long-term health. Thus, if your training volume is high and you want to lose weight, it is important to aim for slow weight loss with a low caloric deficit per day, and only over a short period of time. Ideally, one should avoid aiming for weight loss by creating an energy deficiency during competition and intensive training phases. It should be noted that even if your weight is stable, it is still possible that you are not eating enough calories and that your risk of injuries, infections, and nutritional deficiencies is increased. Indeed, by being energy deficient, the body adapts and decreases its resting metabolism, which means that you will expend fewer calories at rest. In the long run, this can negatively affect your ability to control your body weight.

RED-S can be detected in women when they stop menstruating. In men, a good indicator is a low testosterone level, which can be detected via a blood test. A normal testosterone level in men is between 10 and 30 nmol/L. Another sign of RED-S is a decrease in sexual desire.

If you suspect that you have RED-S, here are some tips for increasing your caloric intake:

  • Add snacks between your meals that contain both carbohydrate and protein such as a fruit with nuts, rice cakes with nut butter, crackers with cheese, or yogurt with fruit.

  • Add a smoothie to your daily diet that contains protein (protein powder, yogurt, tofu or cow or soy milk) and fruits.

  • Add good fats to your diet such as ground flaxseeds or chia seeds, nuts, olive oil and avocados.

  • Don’t hesitate to get help from a Sports Dietitian who can help you determine your caloric needs, analyze your diet, advise and build a personalized meal plan for you.



Kathryn Adel, MS, RD, CSSD, LD

Kathryn is a Registered Dietitian Nutritionist, a gut health specialist and a Certified Specialist in Sports Dietetics (CSSD). She holds degrees in both Kinesiology and Nutrition, as well as a Master's degree in Sports Nutrition from Laval University in Canada. She is also an accomplished athlete, having ran track and cross-country at a national level. She also completed numerous triathlons and running events ranging from 5 km to marathon. She works extensively with athletes of all levels, helping them achieve optimal performance through personalized approaches. Kathryn is also trained to help endurance athletes who suffer from gastrointestinal symptoms during exercise. She is experienced with the Low FODMAP Diet for Irritable Bowel Syndrome (IBS) and is certified by Monash University in Australia. Her extensive training and experience in Sports Nutrition along with her personal experience as an endurance athlete allows her to help athletes achieve peak performance. Outside of her work, Kathryn is an avid runner, surfer and traveler. For more information and to contact Kathryn, you can visit her website at or email her at

Janet Carter, MS, RD, LDN, CLS, CPT

Janet Carter is a registered dietitian with a Master’s degree in nutrition science from Boston University and over 15 years of experience. She’s also a clinical lipid specialist (heart disease expert) and a certified personal trainer, in addition to being an avid runner and triathlete. She has completed 11 marathons, including Boston, and over 70 triathlons, including 2 Ironman finishes. Her knowledge of performance nutrition, coupled with her practical experience allows her to help athletes achieve peak performance.

For more information & to contact Janet, email

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