October 2024 Issue
Focus on Fitness: Overtraining Syndrome
By Carrie Dennett, MPH, RDN
Today’s Dietitian
Vol. 26 No. 8 P. 44
Why “more is better” has a tipping point for physical activity.
There’s no escaping the message that physical activity is good for health and that many Americans need to exercise more. People who go from sedentary to meeting the guidelines of 150 minutes of moderate activity per week reap the greatest benefits,1 and while there are additional benefits from higher levels of activity, the law of diminishing returns applies—despite the common ethos that “more is better.” In fact, excessive exercise has the potential to cause lasting harm, especially in the absence of adequate nutrition, rest, and recovery.
A hallmark example is overtraining syndrome (OTS)—a persistent imbalance between training and/or nontraining stress and recovery—which causes decreased performance and fatigue.2 Chronic low energy availability and depletion of the body’s repair mechanisms can impair multiple metabolic pathways, including those impacting endocrine and immune function, so athletes or others with OTS become deconditioned despite their high level of activity. This can last for several months or even years.3
From Overreaching to OTS
Functional overreaching is a short-term training overload that causes decreased performance for up to two weeks, followed by supercompensation—neurological, structural, and hormonal adaptation and subsequent improvement in performance. It’s a common strategy, but when the decreased performance lasts longer and isn’t followed by supercompensation, the overreaching becomes nonfunctional. If this persists, the individual may develop OTS.4
Arizona-based dietitian and strength coach Abby Chan, MS, RDN, RYT, co-owner of EVOLVE Flagstaff, says she sees cases of overtraining weekly. If they’re overreaching, the intervention is easier. “You may want that effect as long as you can come back down from that stress and be able to recover.” However, if someone has progressed to OTS, that involves a more nuanced intervention and a much longer road to recovery, she says. If someone has developed relative energy deficiency in sport (RED-S), which shares some of the same triggers and pathways,5 there may be major long-term, even lifelong, health implications.
Prevalence and Diagnosis
OTS was first recognized more than 90 years ago.2 Its estimated prevalence is 15% to 60%6 and appears to be highest in endurance sports such as swimming, triathlon, road cycling, and rowing.2 Clinical manifestations include general fatigue, insomnia, changes in digestive function, irritability, depression, apathy, and lack of concentration, but with no gold standard diagnostic test, OTS is a diagnosis of exclusion4 and generally isn’t diagnosed unless an athlete hasn’t fully recovered after a few weeks or months of rest.
Recent research from the Endocrine and Metabolic Responses on Overtraining Study (EROS) identified multiple biomarkers that could help with diagnosis,3 although the study authors said it appears that OTS results from “synergistic combinations and interactions of negative factors” that are unique to each athlete.6
Risk Factors
The classic risk factors for OTS are excessive training or an excessive increase in training intensity or volume—nonfunctional overreaching—but EROS identified several additional triggers3:
• unrefreshing sleep and/or lack of good sleep hygiene;
• high cognitive demands from working or studying more than seven hours per day during intense training periods;
• carbohydrate intake below 5 g/kg/day, protein intake of less than 1.6 g/kg/day, and/or calorie intake of less than 35 kcal/kg/day for more than eight weeks; and
• skipping more than one meal per week when carbohydrate, protein, or calorie intake is low.
“I see low energy availability in a lot of athletes stuck in ‘The lighter I am, the better I’ll perform’ mode. And part of their quest for lightness is a lot of exercise,” says Nancy Clark, MS, RD, CSSD, a Boston-area private practice sports dietitian and author of Nancy Clark’s Sports Nutrition Guidebook. “You try to tease out, ‘Do you have a coach?’ If yes, ‘Do you follow your coach’s program?’ Some athletes do more than their coach recommends. Some of them don’t have a coach, and they’re just self-coaching.”
Chan says her most at-risk athlete isn’t an elite athlete—probably because they’ve had enough team support that they understand the basics of nutrition and recovery—it’s a recreational athlete who wants to lose weight, change their body shape, or improve their health. For example, they might want to train for a 5K, enjoy it, and then decide to train for a 10K or a marathon without understanding the impact of increasing their training volume. “They’re still coming from a ‘change my body, lose weight’ standpoint when I’m like, ‘No, now we have to really think of you as an athlete, whether your brain sees it that way or not.’”
Periodization of training sessions hasn’t reduced OTS prevalence, partly because other OTS triggers,3 such as improper nutritional intake7 and nontraining stressors, are still present. Chan points out that stress is stress, whether it’s training, work, or life stress. “The body is having some level of a hormonal response to that stressor, which is going to reduce recovery and shift how the body is using energy.” Excessive stress can also provoke a chronic inflammatory response, affecting training and sleep. She says when she’s working with athletes, she asks them about sleep, home life, relationships, and jobs. “Are you traveling all the time? Are you in med school? Are you on your feet all day? I think that’s something that people don’t understand. They think, ‘I’m not training, so it’s not stressful,’ and I’m like, well, that’s where the wheels fall off.”
OTS and Glucose Tolerance
Research has found that athletes with OTS develop biomarkers resembling those of sedentary individuals rather than those of healthy athletes.3 A 2021 study8 looked at the short-term effects on physiological adaptation to exercise, mitochondrial function, and glucose metabolism in 11 healthy subjects. The four-week intervention gradually increased the volume of high-intensity interval training to identify the point where exercise no longer resulted in positive metabolic outcomes. Performance stagnated in week three—152 minutes of high-intensity interval training—then peaked during week four recovery. However, mitochondrial function and glucose tolerance decreased in week three and only partially recovered during week four. An additional “real world” comparison between 15 healthy free-living endurance athletes and 12 matched controls who exercised less than seven hours per week found that only the athletes had impaired glucose tolerance.
“If an athlete is training and you start to see their A1c or their cholesterol elevated—or you start to see a low A1c but there’s evidence of insulin resistance—the answer isn’t to eat less and move more or decrease fat or carb intake or whatever,” Chan says. “These are all ramifications of too much stress on the body and not having enough rest, recovery, and nutrition.”
OTS and Eating Disorders
Chan says she sees two primary pathways to OTS. The first starts with an eating disorder. The second starts with a lack of knowledge about nutrition and appropriate training. Both can involve exercise dependence or addiction. If the athlete’s identity—or their sport, coaching, or community culture—is performance-based, regardless of the original pathway, “that has physiological and mental health outcomes, and they land in the same place.”
Clark explains it’s often unclear if overtraining is part of an eating disorder or if undernutrition is part of overtraining. “Which came first? It varies from person to person.” She says athletes who are struggling with eating disorder behaviors may not get help because they’re ashamed. “So many of my clients know that their eating is off, but it takes them years to ask for help.”
Tips for RDs
Chan says it’s important to remember that at least one in 10 patients is likely to have a history of an eating disorder or disordered eating. “People move their bodies for a variety of different reasons, and they’re going to be looking to us as experts. If they’re training, are they eating at least three meals and maybe one to two snacks? Are they meeting their carb needs and eating enough calories? If someone’s training for more than an hour, we need to get some fuel on board, and that fuel needs to be carbohydrates.”
Clark says nonsports dietitians may miss some nutritional red flags. “The dietitian will look at their diet and they’re only eating healthful foods, but maybe there’s not enough calories, and that’s why they’re tired,” she says. “If a person has been doing more exercise and getting fewer and fewer benefits, it’s important that they sit back and assess, ‘Why am I doing this?’” If they’re getting enough calories, carbs, protein, and fat, and they’re still not improving, are they getting enough rest days? “Maybe their body needs more rest than another person’s body.”
— Carrie Dennett, MPH, RDN, is the nutrition columnist for The Seattle Times, owner of Nutrition By Carrie, and author of Healthy for Your Life: A Non-Diet Approach to Optimal Well-Being.
References
1. US Department of Health and Human Services. Physical Activity Guidelines for Americans, 2nd edition. Washington, DC: US Department of Health and Human Services; 2018.
2. Armstrong LE, Bergeron MF, Lee EC, Mershon JE, Armstrong EM. Overtraining syndrome as a complex systems phenomenon. Front Netw Physiol. 2022;1:794392.
3. Cadegiani FA, da Silva PHL, Abrao TCP, Kater CE. Diagnosis of overtraining syndrome: results of the endocrine and metabolic responses on overtraining syndrome study: EROS-DIAGNOSIS. J Sports Med (Hindawi Publ Corp). 2020;2020:3937819.
4. Carrard J, Rigort AC, Appenzeller-Herzog C, et al. Diagnosing overtraining syndrome: a scoping review. Sports Health. 2022;14(5):665-673.
5. Stellingwerff T, Heikura IA, Meeusen R, et al. Overtraining syndrome (OTS) and relative energy deficiency in sport (RED-S): shared pathways, symptoms and complexities. Sports Med. 2021;51(11):2251-2280.
6. Cadegiani FA, Kater CE. Novel insights of overtraining syndrome discovered from the EROS study. BMJ Open Sport Exerc Med. 2019;5(1):e000542.
7. la Torre ME, Monda A, Messina A, et al. The potential role of nutrition in overtraining syndrome: a narrative review. Nutrients. 2023;15(23):4916.
8. Flockhart M, Nilsson LC, Tais S, Ekblom B, Apró W, Larsen FJ. Excessive exercise training causes mitochondrial functional impairment and decreases glucose tolerance in healthy volunteers. Cell Metab. 2021;33(5):957-970.e6.