Detecting and preventing low energy availability in male tactical athletes

By Brandon Lee, MS, RD, CCRP

Energy availability (EA) is a crucial aspect of nutrition that often gets overlooked. It represents the amount of energy (calories) left to support normal bodily functions after exercise or physical training. Athletes who don’t consume enough calories to support their activity levels and their normal body functions can end up hurting their health and athletic performance. This state is known as low energy availability (LEA).

Historically, LEA was considered a problem only women had, yet growing evidence shows it can be just as harmful to men’s health and performance. Understanding the signs and risks associated with LEA can help male tactical athletes—including Service Members—improve their health and perform at their best.

Causes of low energy availability

LEA occurs when there isn’t enough energy to meet the physical demands placed on the body, including daily activity, planned exercise, and the physical demands of active occupations such as infantry, divers, and special operations forces. The root cause of LEA is getting too few calories, burning too many calories or for a long period of time, or both. Common reasons for LEA include disordered eating or eating disorders, intentionally decreasing calories to change body mass or composition (weight cutting), or high levels of energy output from physical activity without getting enough to eat or drink (calories). LEA is particularly common among people who participate in high-intensity, long-duration, high-frequency training programs such as ruck marches or selection training. When you don’t get enough calories with the physical stress of high-intensity training, your health, performance, and wellness can all suffer.

LEA can affect a Service Member or any other type of tactical athlete who’s physically active and not getting enough to eat or drink. Some research has found LEA to be common among athletic communities who emphasize low body weight, such as swimmers, gymnasts, wrestlers, martial artists, and even bodybuilders. But there's little to no research on LEA in military personnel. Service Members who may be at risk for LEA include those at basic military training, when recruits must do physically demanding tasks and total energy output can exceed ~4,400 kcal/day. Tactical athletes whose jobs require high physical demands may also be at risk, particularly when taking specialist military training courses and doing field exercises where access or the ability to eat and drink is limited.

Risks associated with low energy availability

If it’s not managed, LEA can lead to other health conditions, such as relative energy deficiency in sport (RED-S). RED-S is a fairly new condition, identified by the International Olympic Committee, which refers to normal body processes shutting down because there aren’t enough calories to sustain life. A subsection of RED-S, the male athlete triad, was introduced in 2017. It’s a new concept compared to the established history, research, and societal awareness of the female athlete triad. Both the male and female athlete triad focus on LEA, impaired bone health, and reduced reproductive function.

Male tactical athletes who don’t get enough calories to support their activity levels are at risk for LEA, RED-S, and the male athlete triad. RED-S can hurt multiple biological systems, including reproductive, bone health, endocrine, immune, metabolic, psychological, cardiovascular, and gastrointestinal. Also, RED-S reduces athletic performance. It decreases endurance performance, training response, judgment, coordination, concentration, and muscle strength, and it increases irritability, depression, and the risk for other injuries.

Although there isn’t much data on energy availability in the tactical community, research on men and women in athletic communities can apply. For example, researchers have found that as energy availability decreased, so did testosterone levels. There’s also evidence showing LEA can hurt bone health.

Bone mineral density is the primary measurement method to evaluate overall bone health and the risk for osteoporosis. Some of the risk factors for low bone mineral density include LEA, low body weight (<85% of ideal body weight), decreased testosterone, running more than 30 miles per week, and a history of stress fractures. Getting enough calories and doing weight training are vital to help you maintain healthy bone mineral density. It’s unclear whether low bone mineral density can be reversed, unlike testosterone levels and LEA, which can be reversed.

Signs and symptoms of low energy availability

Service Members should monitor for signs and symptoms of LEA, including low energy levels, fatigue or feeling tired all the time, recurring bone stress injuries, lower sex drive, loss of appetite, unintentional weight loss, and reductions in muscle mass or strength. LEA is diagnosed when one of the following is present: reduced resting metabolic rate (RMR) compared to body weight or muscle mass, unintentional weight loss resulting in a new low set point, low body mass index (BMI), and reduced metabolic hormones and related biomarkers that your doctor might look for. Men with LEA can have low sperm count or reduced sex drive. They can also develop bone stress injuries, osteopenia, or osteoporosis. If you’re concerned you have LEA, consult with a registered dietitian or other trusted health care provider before making any dietary changes.

How to prevent LEA

All military personnel must maintain their physical health and be mission-ready at all times. Physical training in an LEA state can put your body and career at risk. Also, LEA can impact home life due to low energy (and sex drive), affecting family engagement and planning. The energy needs of a tactical athlete can vary greatly depending on the frequency, intensity, duration, type, amount, and progression of training.

The first and most important line of defense to prevent LEA is to make sure you get enough calories to meet both the energy needs of normal bodily functioning and the energy needs of your individual activity level.

Consider meeting with a registered dietitian to discuss a nutrition plan that fits your lifestyle, training demands, fitness goals, and personal preferences. Nutrition counseling sessions typically cover improving food availability, correcting food misconceptions, changing mealtime schedules, resolving food insecurities, and supplementing your diet. Nutrition interventions focus on eating and drinking more to increase your calories, decreasing how much you exercise, or both.

Many people with LEA also find it helpful to meet with a certified strength and conditioning specialist. Strength and conditioning specialists evaluate your current lifestyle and goals and then develop a comprehensive, individualized training program to help you meet those goals. You might also consider working with a mental performance coach to help you develop self-mastery, refine your career and performance goals, improve your emotional intelligence, and ensure your daily actions take you one step closer to reaching your goals.

Bottom line

Energy availability is essential for recreational and professional athletes to support normal body functions and the demands of military duty and physical training. Low energy availability can hurt health and performance. To prevent LEA, tactical athletes must get enough calories (energy) to support their physical activity from exercise and occupational demands. Human performance optimization teams, such as Holistic Health and Fitness (H2F), are available to support you in reaching and maintaining your athletic performance, health, and fitness goals.

Disclosure: The opinions and assertions expressed herein are those of the authors and do not reflect the official policy or position of USU or DoD. The contents of this publication are the sole responsibility of the authors and do not necessarily reflect the views, opinions, or policies of The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc. Mention of trade names, commercial products, or organizations does not imply endorsement by the U.S. Government. The authors have no financial interests or relationships to disclose.