Bone Density Loss in Lean Male Runners Parallels Similar Issue in Women

Theodore Bosworth

June 22, 2022

Similar to a phenomenon already well documented in women, inadequate nutrition appears to be linked to hormonal abnormalities and potentially preventable tibial cortical bone density loss in athletic men, according to results of a small, prospective study.

Based on these findings, "we suspect that a subset of male runners might not be fueling their bodies with enough nutrition and calories for their physical activity," reported Melanie S. Haines, MD, at the annual meeting of the Endocrine Society.

This is not the first study to suggest male athletes are at risk of a condition equivalent to what has been commonly referred to as the female athlete triad, but it enlarges the objective data that the phenomenon is real, and it makes insufficient availability of energy the likely cause.

In women, the triad is described as a lack of adequate stored energy, irregular menses, and bone density loss. In men, menstrual cycles are not relevant, of course, but this study like others suggests a link between the failure to maintain adequate stores of energy, disturbances in hormone function, and decreased bone density in both men and women, Haines explained.

RED-S vs. Male or Female Athlete Triad

"There is now a move away from the term female athlete triad or male athlete triad," Haines reported. Rather the factors of failing to maintain adequate energy for metabolic demands, hormonal disturbances, and bone density loss appear to be relevant to both sexes, according to Haines, an endocrinologist at Massachusetts General Hospital and assistant professor of medicine at Harvard Medical School, both in Boston. She said several groups, including the International Olympic Committee (IOC), have transitioned to the term RED-S to apply to both sexes.

"RED-S is an acronym for relative energy deficiency in sport, and it appears to be gaining traction," Haines said in an interview.

According to her study and others, excessive lean body mass from failure to supply sufficient energy for physiological needs "negatively affects hormones and bone," Haines explained. In men and women, endocrine disturbances are triggered when insufficient calories lead to inadequate macro- and micronutrients.

In this study, 31 men aged 16-30 years were evaluated. Fifteen were in the athlete group, defined by running at least 30 miles per week for at least the previous 6 months. There were 16 control subjects; all exercised less than 2 hours per week and did not participate in team sports, but they were not permitted in the study if their body mass index exceeded 27.5 kg/m2.

Athletes vs. Otherwise Healthy Controls

Conditions that affect bone health were exclusion criteria in both groups, and neither group was permitted to take medications affecting bone health other than dietary calcium or vitamin D supplements for 2 months prior to the study.

Tibial cortical porosity was significantly greater – signaling deterioration in microarchitecture – in athletes, compared with control subjects (= .003), according to quantitative computed tomography measurements. There was also significantly lower tibial cortical bone mineral density (= .008) among athletes relative to controls.

Conversely, tibial trabecular measures of bone density and architecture were better among athletes than controls, but this was expected and did not contradict the hypothesis of the study.

"Trabecular bone refers to the inner part of the bone, which increases with weight-bearing exercise, but cortical bone is the outer shell, and the source of stress fractures," Haines explained.

The median age of both the athletes and the controls was 24 years. Baseline measurements were similar. Body mass index, fat mass, estradiol, and leptin were all numerically lower in the athletes than controls, but none were significant, although there was a trend for the difference in leptin (= .085).

Hormones Correlated With Tibial Failure Load

When these characteristics were evaluated in the context of mean tibial failure load, a metric related to strength, there was a strongly significant positive association with lean body mass (R = 0.85; < 0.001) and estradiol level (R = 0.66; = .007). The relationship with leptin also reached significance (R = 0.59; = .046).

Unexpectedly, there was no relationship between testosterone and tibial failure load. The reason is unclear, but Haines's interpretation is that the relationship between specific hormonal disturbances and bone density loss "might not be as simple" as once hypothesized.

The next step is a longitudinal evaluation of the same group of athletes to follow changes in the relationship between these variables over time, according to Haines.

Eventually, with evidence that there is a causal relationship between nutrition, hormonal changes, and bone loss, the research in this area will focus on better detection of risk and prophylactic strategies.

"Intervention trials to show that we can prevent stress factors will be difficult to perform," Haines acknowledged, but she said that preventing adverse changes in bone at relatively young ages could have implications for long-term bone health, including protection from osteoporosis later in life.

The research presented by Haines is consistent with an area of research that is several decades old, at least in females, according to Siobhan M. Statuta, MD, a sports medicine primary care specialist at the University of Virginia, Charlottesville. The evidence that the same phenomenon occurs in men is more recent, but she said that it is now well accepted that there is a parallel hormonal issue in men and women.

"It is not a question of not eating enough. Often, athletes continue to consume the same diet, but their activity increases," Statuta explained. "The problem is that they are not supplying enough of the calories they need to sustain the energy they are expending. You might say they are not fueling their engines appropriately."

In 2014, the International Olympic Committee published a consensus statement on RED-S. They described this as a condition in which a state of energy deficiency leads to numerous complications in athletes, not just osteoporosis. Rather, a host of physiological systems, ranging from gastrointestinal complaints to cardiovascular events, were described.

RED-S Addresses Health Beyond Bones

"The RED-S theory is better described as a spoke-and-wheel concept rather than a triad. While inadequate energy availability is important to both, RED-S places this at the center of the wheel with spokes leading to all the possible complications rather than as a first event in a limited triad," Statuta said in an interview.

However, she noted that the term RED-S is not yet appropriate to replace that of the male and female athlete triad.

"More research is required to hash out the relationship of a body in a state of energy deficiency and how it affects the entire body, which is the principle of RED-S," Statuta said. "There likely are scientific effects, and we are currently investigating these relationships more."

"These are really quite similar entities but have different foci," she added. Based on data collected over several decades, "the triad narrows in on two body systems affected by low energy – the reproductive system and bones. RED-S incorporates these same systems yet adds on many more organ systems.

The original group of researchers has remained loyal to the concept of the triad that involves inadequate availability of energy followed by hormonal irregularities and osteoporosis. This group, the Female and Male Athlete Triad Coalition, has issued publications on this topic several times. Consensus statements were updated last year.

"The premise is that the triad leading to bone loss is shared by both men and women, even if the clinical manifestations differ," said Statuta. The most notable difference is that men do not experience menstrual irregularities, but Statuta suggested that the clinical consequences are not necessarily any less.

"Males do not have menstrual cycles as an outward marker of an endocrine disturbance, so it is harder to recognize clinically, but I think there is agreement that not having enough energy available is the trigger of endocrine changes and then bone loss is relevant to both sexes," she said. She said this is supported by a growing body of evidence, including the data presented by Haines at the Endocrine Society meeting.

Haines and Statuta report no potential conflicts of interest.

This article originally appeared on, part of the Medscape Professional Network.


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