RED-S: Accidental Under Fueling and the Male Cyclist

RED-S or relative energy deficiency in sport (RED-S) while not a new phenomenon, is still not always easy to diagnose, especially among male cyclists.

Low energy availability (LEA) basically means a mismatch between calories burned and calories consumed. LEA causes adverse health and performance outcomes including poor bone health and higher risk of bone stress injuries including fractures in both female and male athletes.

Originally called the Female Athlete Triad, for a long-time research focused just on the effects of energy deficiency in female athletes. Today, there is a better understanding of how it affects the male athlete as well, but athletes and their doctors do not always have it on their radar.

Cyclists are a particularly high-risk group for RED-S because they are not aware they are under fueling, and for them the signs of poor bone health are not as obvious given that cycling is a non-weight-bearing sport. Often, they don’t know there is a problem until they experience a traumatic fracture.

A Cycling Weekly survey of 868 riders from earlier this year found that one in five amateur riders are under fueling, putting them at risk for RED-S. And 30% of female and 15% of male respondents reported symptoms of RED-S. That increased to 40 and 36%, respectively, in semi-professionals.

A British cyclist, Doug Bentall, recently wrote about his experience with RED-S in “RED_S: not just a female phenomenon” for the British Journal of Sports Medicine.

Bentall was a runner when he was in school but was forced to give it up after a knee injury at university. Afterwards he took up cycling for leisure, and rode for fun through most of his 30s and 40s. Then at 48 he started working with a cycle trainer so he could pursue it more competitively.

During training, he noticed that he was losing weight but wasn’t really concerned at first, explaining that he wasn’t being vigilant about the nutritional needs of being a competitive cyclist. It wasn’t until he turned 50 and was training for his first duathlon that he became concerned about his health.

He wrote, “At the end of the year, I qualified for the European Age Group Duathlon in Spain in April 2017. I entered a local cross-country event and I won the 50 years+ race, but afterwards, I had difficulty walking. In my opinion, I thought I had just pulled a hamstring as that was what my symptoms felt like. I took some painkillers and ran the Masters’ event the next week, but the problem was still there. With the European Age Group Duathlon only a month away. I stopped running completely and stuck to the bike.”

Bentall was eventually referred to a sports injury specialist who diagnosed him with a stress fracture in the hip and low vitamin D levels. He wasn’t given a bone scan though. It wasn’t until later when he enrolled in a study on male cyclists that he was able to get one done, and it showed he had low bone mineral density in his spine, a classic symptom of RED-S in male cyclists.

Challenges of Diagnosis

On why warning signs are often missed, Dr. Nicky Keay, a sports and dance endocrinologist and member of British Association Sport and Exercise Medicine, told OTW, “The obvious clinical sign of RED-S in female athletes/dancers is often amenorrhoea. In men the equivalent will be loss of libido and decreased early morning erections. Furthermore, unlike running, cyclists will not present with stress fractures. So suboptimal bone health may not be recognized.”

“Therefore, early identification of athletes at risk of developing health and performance adverse consequences is an important strategy,” she said.

Bentall noted in British Journal of Sports Medicine that he, like probably a lot of other male athletes, had thought that RED-S was a female phenomenon and was associated more with eating disorders. When they have a healthy relationship with food, they don’t even consider that they might possibly at risk for RED-S.

It is not always related to an eating disorder or weight loss, however. The under fueling can happen accidentally and in some cases it is more about timing of meals than how much you eat in a given day. Not properly fueling up before exercise is enough to cause energy deficiency.

Another challenge in diagnosing RED-S is identifying the cause of low testosterone, because while it can be a symptom of LEA it can also be a symptom of a too high training load.

Getting an accurate diagnosis of LEA in male cyclists is further complicated by the fact that unlike in runners a stress fracture is not always an early warning sign of poor bone health caused by low EA. In addition, cyclists are already at risk of poor bone health because of the non-weight bearing nature of the sport.

What the Research Says

Dr. Keay has a particular interest in how RED-S affects the cycling community.

In “Low energy availability assessed by a sport-specific questionnaire and clinical interview indicative of bone health, endocrine profile and cycling performance in competitive male cyclists,” published in British Medical Journal Open Sport & Exercise Medicine, she and her co-authors used a combination of a sport-specific questionnaire and clinical interview (SEAQ-I) and dual energy X-ray absorptiometry (DXA) bone mineral density and body composition scans and blood tests for endocrine markers to evaluate 50 competitive male road cyclists.

According to the data collected, those cyclists identified as having LEA from the SEAQ-I had lower lumbar spine bone mineral density (BMD) than those with adequate EA. Low EA was observed in 28% of the cyclists. Low lumbar spine BMD was found in 44% of cyclists. EA was the biggest determinant of lumbar spine BMD Z-score (p < 0.001). Among those cyclists with the low EA, lack of previous load-bearing sport was associated with the lowest BMD (p = 0.013).

Low vitamin D and testosterone levels were also associated with chronic low EA. LEA was also found to affect cycling performance. In the study, cyclists with chronic LEA were underperforming.

Dr. Keay said their findings reinforce the importance of a detailed history. “Questionnaire alone can lead to athletes giving ‘correct’ answers on nutrition and training load. Clinical interview gave details on the temporal aspects of EA in the context of cycle training schedule: whether riders were experiencing acute intermittent LEA, as with multiple weekly fasted rides, or chronic sustained LEA with prolonged periods of suppressed body weight. Additionally the SEAQ-I provided insights on attitudes to training and nutrition practices,” she wrote in a blog for the British Journal of Sports Medicine.

She warned against the used of periodized carbohydrate intake for low intensity sessions in athletes with chronic LEA, saying “increasing training load improves performance, but this training is only effective if fueling is tailored accordingly.”

Another study, “Alternate-Day Low Energy Availability During Spring Classics in Professional Cyclists”, published in the Human Kinetics Journal also found that weight loss isn’t always the best indicator of RED-S. In an analysis of cyclists on the Mitchelton-Scott men’s team, the researchers found that while the men stayed consistent in weight, those with reduced caloric intake experienced hormonal change.

Tips for Sports Medicine Doctors

So how should sports medicine doctors handle diagnostic challenges of RED-S when trying to protect the health of their athletes? Bentall suggests three learning points for clinicians dealing with RED-S:

• Coaches, physiotherapists and medical professionals all need to be aware of this risk in amateur cyclists, both women and men.
• When training seriously, cyclists may be under fueling without realizing it.
• There needs to be more education for cyclists about RED-S and the importance of matching nutrition to training levels.

He wrote, “I appreciate that many people may benefit greatly from losing weight, but there is not enough information available warning the lightweight middle-aged men in lycra to take care.”

Sports medicine experts agree that when an athlete presents with a bone stress injury, under fueling should be considered as a possible underlying cause of poor bone health.

Dr. Keay, when asked how she would advise sports medicine doctors, said, “Ask questions relating to morning erections, nutritional practices etc. As RED-S is a diagnosis of exclusion run some baseline tests and consider DXA as indicated. Addressing behavioural change is key.”