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How Much Do You Know About the Male Athlete Triad?

Low sex drive, low sperm count, and a greater rate of injury - the combo of underfueling and overtraining has major consequences for men in endurance sports.


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It’s the dietary trap just about every triathlete falls into at some point: The latest app, book, or diet program swears to help you become lean and mean (or your money back, guaranteed). You quickly pull out your credit card, start reading, and follow the plan diligently. And for many, these get-lean-quick fixes work. Sure, you’re cutting out food groups and feeling a little tired when working out on an empty stomach, but hey, you can almost see the outline of an ab muscle! 

The problem with these quick fixes is that even if they work in the short-term, when kept up for weeks and months you may be asking your body to make more long-term adjustments to cope with a chronic energy deficit from not eating enough for your activity. Ultimately, this can result in dysfunction with the hormones that control your resting metabolic rate and reproductive processes.

It’s likely you’ve heard of this before in descriptions of Relative Energy Deficiency in Sport (RED-S) and the Female Athlete Triad, a condition that is defined by low energy availability (LEA), menstrual dysfunction, and low bone mineral density. There’s a large body of research on how the combination of overtraining and underfueling affects women, but that doesn’t mean the condition is exclusive to those born without a Y chromosome. Emerging data has also identified males as being impacted by low energy availability, and with it, greater awareness of the Male Athlete Triad.

What is the Male Athlete Triad?

While research on the Female Athlete Triad spans three decades, the scientific data on how males are impacted by lower energy availability is a relatively new concept. In 2021, the American College of Sports Medicine (ACSM) released a two-part consensus paper (which you can read here and here) discussing the Male Athlete Triad and calling for more research to better understand this condition.

Still, there are some things we already know about the Male Athlete Triad. Similar to females, low energy levels are the driving force behind the Triad in males. Energy availability is defined as the energy remaining for normal bodily processes after the energy cost of training. This is often expressed as the value of a calorie per fat-free mass (FFM). When the body is asked to function without adequate calories, regardless of the reason, it is forced to adjust other systems. This forms the three corners of the Male Athlete Triad:

  • Low energy availability (LEA)
  • Changes to reproduction function
  • Osteoporosis or low bone mineral density

Low Energy Availability

The body is one smart piece of machinery.  If you don’t provide it with enough energy (food) to support both living and exercise activity, then it will adapt.  Once energy demands are not met, compensatory adaptations take place that include the suppression of resting metabolic rate, loss of body weight, and suppression of metabolic hormones such as T3 and leptin (both of which help control hunger and metabolism). The exact definition of low EA and what threshold will produce these changes has yet to be determined in males. In addition, no standard protocol exists for identifying low EA among male athletes. However, the prevalence of exercising men reporting EA values below 30 kcal/kg fat-free mass per day is similar to what has been reported in women, which is around 56% versus 51% in adolescent male and female athletes in a variety of sports.  

RELATED: Your “Good” Diet Could Be Ruining Your Life

Changes to reproductive function

LEA can cause a condition known as hypogonadism, where the sex glands (or “gonads”) produce little, if any, sex hormones. In men, this can manifest in several ways:

  • Alterations in hormones, such as testosterone
  • Irregular and/or low sperm count
  • Reduced sex drive

To date, research has not identified a clear line where calories/FFM level reproductive function is impaired. However, there is strong evidence to support a greater energy deficit (around 1100 kcal per day) is required in men than in women to cause alterations to these hormones. The amount of variation in certain metabolic hormones, such as T3 and leptin, varies greatly between studies, and much more research is needed to gain a clear understanding of how caloric deficits play out in the male athlete’s body.

Bone mineral density

Most concerning to triathletes is the long-term influence that hypogonadism, combined with low energy availability, has on bone mineral density. In addition, there is a correlation between the prevalence of impaired bone health and higher bone stress injuries in sports that emphasize leanness or lower body weights/body compositions. Just as in females, bone mineral density/bone stress injuries can be a result of long-term adaptations to chronic energy deficit. For men, the most common bone stress injuries take place in the lumbar-spine region in distance runners, cyclists, swimmers, and jockeys. While data is limited to cross-sectional studies, some, but not all, studies have indicated lower femoral neck and/or spine bone mineral density in cyclists when compared to recreational active individuals or sedentary controls. Regardless, low bone mineral density is more common in those competing in leanness or low-impact/non-impact load sports when compared with men in nonleaness sports.  

Who is at risk for the Male Athlete Triad?

All male athletes are at risk for the Male Athlete Triad. However, sports that emphasize leanness or muscularity, weight-class sports, aesthetic sports (sports where the athletes are judged according to how they look), and endurance sports are at the greatest risk. Triathletes check the boxes in multiple categories in this case: leanness, endurance, and aesthetics are all core elements of the sport. (If the underwear run in Kona during the Ironman World Championships isn’t an example of these elements on parade, I don’t know what is!)

Competition level matters very little in the Male Athlete Triad. Whether a back-of-the-pack amateur or an elite high-performance athlete, it is possible for any active male to develop one or all three of the triad’s components if they are shorting their body’s energy needs. Warning signs for inadequate energy include:

  • A loss of more than 10% of normal body weight in six months
  • Disordered eating (restrictive, irregular, or inflexible eating patterns)
  • Extremely high training volumes
  • An emphasis on perfection
  • Weight-cycling (not maintaining weight)
  • Body dissatisfaction
  • Recurrent stress fractures
  • Low libido

Fuel for health and performance

Athletes training several hours (or more) per day should aim for eating every three to four hours. This should include three meals per day and at least two snacks. Maintaining a consistent eating pattern, tailored to your individual caloric needs and training plan, should allow for adequate fueling and recovery from exercise. 

Is it possible to lose weight safely and in a way that won’t negatively impact your health? Absolutely! Each person has to find their own balance to support training and recovery with a diet filled with plenty of fruits, vegetables, whole grains, dairy, lean meats, fish and healthy fats. A healthy diet includes all macronutrients, including carbohydrates, proteins and fats and focuses on the quality of those areas not just the quality. With that said, creating a calorie deficit of 300-500 calories fewer than your established calorie needs should be appropriate to help jump start weight loss in a sustainable fashion. Another important aspect is to maintain protein at a higher level (up to 30% of total calories), while maintaining a deficit to minimize muscle loss and help with hunger. The off-season is the best time to accomplish this, but if you’re in-season pay close attention to your overall energy, hunger, recovery, and training and don’t ever skip pre-workout snacks or post-workout recovery carbohydrates and protein in any workout with intensity lasting over an hour. 

More information can be found by visiting the nonprofit, evidence-based website The Female and Male Athlete Triad Coalition, which provides free educational materials, snack ideas, infographics, and personal athlete stories concerning the Triad. 

RELATED: 5 Signs You’re Not Eating Enough

Male Athlete Triad: the bottom line

While the Female Athlete Triad is more well-known, the Male Athlete Triad is a syndrome of three interrelated conditions characterized by low energy availability (“under-fueling”), suppression of metabolic and reproductive hormones, and impaired bone health. Male endurance athletes, including triathletes, are at greater risk of alterations in the body’s processes and subsequent bone stress injuries due to the emphasis on lean physique and energy demands of the sport. 

Working with a registered dietitian (use the Academy of Nutrition and Dietetics expert finder to search for a credentialed professional near you) can help ensure you are meeting your energy requirement. They can also help you tailor your intake to optimize adaptations and recovery from workouts. By fueling with the critical calories and nutrients your body needs to maintain bone health and overall health, male athletes can set themselves up for a long, happy triathlon career.

Kim Schwabenbauer, PhD, RD, CSSD, LDN, is a former professional triathlete turned registered dietitian, professor, consultant, speaker and triathlon coach with an emphasis in overall health, wellness and sports nutrition.