We’ve come to worship the cult of hustling in modern America. We see this on social media, in the corporate world and also with exercise. With pursuits like Spartan races, triathlons and other endurance races gaining popularity, doctors are seeing more patients with ailments and injuries resulting from overtraining combined with underfueling. People pursuing challenging athletic endeavors should understand that if they work out hard, they need to eat hard, too. 

There’s no denying that physical activity is an essential element for overall health and wellbeing. It may even help reduce risk for cognitive decline during aging. But as is true even for water and oxygen, just because something is required doesn’t mean more is always better. When training for a specific event or even just incorporating exercise into everyday life for the purpose of fat loss, building muscle, or supporting mental health, it’s easy for patients (and their doctors!) to get caught up in the mentality of hitting things harder, faster and more frequently. In and of itself, training hard isn’t a problem. Combined with inadequate rest and nutritional replenishment, however, it’s a recipe for illness and injury.

A powerful example of overtraining and underfueling is the female athlete triad, which is characterized by low energy intake and availability, menstrual dysfunction (typically amenorrhea), and low bone mineral density. Women who develop female athlete triad in younger years may continue to have problems later in life owing to the long-term influence of the hormonal imbalances and skeletal changes when they were younger. 

Another consequence of hitting things too hard without sufficient attention to nourishing the body and getting adequate rest is what has been dubbed “famine response hypothyroidism.” This is a downregulation of metabolism secondary to someone asking their body to do too much while providing it with too little—that is, overtraining and underfueling. This has been observed in patients who combine exercise with perhaps overzealous calorie restriction and it manifests as hypothyroidism owing to decreased production of T3 and increased production of reverse T3 (rT3) – often with a normal TSH. (This is just one example of why TSH and T4 are often not sufficient for identifying and diagnosing thyroid dysfunction.) A patient dealing with this may experience the unpleasant signs and symptoms of hypothyroidism and ask, “Why me?” but the truth is, this slowing of metabolism is a protective mechanism. Elevated rT3 combined with depressed T3 is the body’s way of putting the brakes on the metabolic rate so the individual doesn’t jettison lean tissue in lieu of the food/fuel they’re not receiving.

It’s possible this is what happened to participants in the TV show The Biggest Loser, many of whom regained much of the weight they lost—and some even more. It was noted that six years after appearing on the show, their metabolic rates were still significantly depressed as their bodies were working to defend their energy stores.

Another consequence of overtraining and underfueling includes the well-known depression of immune system function athletes experience from overtraining. This often manifests as chronic upper respiratory tract infections and other recurring or recalcitrant illnesses, as well as GI symptoms, possibly owing to compromised gut function. It can also result in insomnia or restless sleep, moodiness or agitation, fatigue, anemia and depression.

So what to do about it? Athletes need not abandon activities that bring them joy and instill a sense of purpose. But they do need to be sure to get adequate calories, with a focus on specific nutrients that support muscle and bone tissue structure, function and recovery. The first and most obvious is protein. A position statement on protein and exercise from the International Society of Sports Nutrition (ISSN) recommends that athletes consume 1.4-3.1 g/kg/d, depending on the individual situation, sport and goals. (This is substantially higher than the oft-cited 0.8 g/kg/d protein intake recommendation for the general public, although some experts believe this is too low for most people.) Whey protein may be especially beneficial for hard-training athletes, but in lieu of whey, supplemental branched chain amino acids (BCAAs) may be helpful. Collagen peptides may also be beneficial because they provide the unique modified amino acids needed as structural components of muscle, bone and connective tissue.

Other supportive nutrients include glutathione, vitamin K2, B vitamins to combat fatigue (some of the symptoms of overtraining mimic those of low B vitamin status), glutamine (especially for supporting gut integrity and the immune system), and vitamin R: rest!

With regard to the sources of these nutrients, athletes can typically tolerate a higher carbohydrate intake than individuals who are more sedentary, but even for athletes, getting proper nutrition no longer means carb-loading and pre-race pasta parties. Many athletes—including record-breaking professional ultra-runners—have embraced low-carb diets. Muscle glycogen replenishment can be accomplished even in the absence of significant dietary carbohydrate.

When it comes to general exercise or training for a specific event, more is not always better. For individuals who live to train and can’t imagine life without engaging in their chosen activity at a high level, more can be okay when it’s accompanied by more food, more nutrients, and more rest and recovery.