Are You Underfueling?
Are You Underfueling?
By Holley Samuel MEd, RD, LD, CSSD, CPT
Underfueling has been discussed more and more lately in any online nutrition space for athletes, and for a good reason. Endurance athletes of all levels may feel the need to hit a certain number on the scale in order to achieve a level of performance and may associate “lighter” with “faster” or “healthier.” In an effort to achieve this, they may reduce their calories, increase their training load (eat less and move more, right?) in order to get the job done. Or maybe an athlete doesn’t even have a goal weight on their radar, but gets too busy at work and forgets to eat enough to fuel their training day to day.
While occasionally missing the mark on your nutrition doesn’t necessarily cause long term harm, consistently underfueling- whether intentional or unintentional- can have detrimental long term effects on performance, health, and body composition. While many athletes do experience the result they desire when they first implement the “eat less move more” strategy, the long term effects of chronic underfueling during training cause this method to backfire.
Underfueling consistently can lead to low energy availability (LEA) and in chronic situations relative energy deficiency in sport (REDs). REDs was formerly referred to as the Female Athlete Triad, but has since been renamed since this condition affects all genders and not only menstruating athletes.
Energy availability refers to the amount of energy your body requires to function properly and the amount of energy you consume as food. It can be described mathematically as:
EA (energy availability)= EI (energy intake in calories)- EEE (exercise energy expenditure in calories) / FFM (fat free mass in kg)
To assess if you are eating enough to support your training and avoid low energy availability, you can start by calculating if your current intake equates to at least 45 calories/kg of fat free mass, as this is the starting point of energy intake required to fuel an active individual.
For example, if you weigh 145 lbs and have 25% body fat (75% fat free mass):
145x0.75=108.75 lbs fat free mass
108.75/2.2= 49.4 kg fat free mass
49.4x45= 2,224 calories per day required to prevent low energy availability (more may be required to enhance performance and varies individual to individual. Energy needs are highly individual)
Once an athlete is chronically experiencing LEA for a longer period of time, they may develop REDs, which affects all body systems. REDs needs to be taken seriously and treated with a team based approach including a physician, dietitian, mental health professional, and coach.
Symptoms of LEA:
Poor performance
Low libido
Poor ability to concentrate
Fatigue
Feeling flat in general
Erratic appetite (feeling very hungry or even experiencing low appetite)
Symptoms of REDs
Recurring injuries or poor healing injuries
Irregular periods or missing periods
Fertility concerns
Low libido and sexual dysfunction
Poor immunity/increase in sickness
Nutrient deficiencies
Delayed growth and development (especially in young populations)
Disordered eating and eating disorders
Image: IOC RED-S consensus 2023, BJSM
Whether an athlete is underfueling intentionally or unintentionally, it is important to identify if this is happening, preferably before these complications occur, especially since REDs is prominent in athletic communities. One study conducted on Australian athletes showed that 80% of participants presented with at least one symptom of REDs with 37% having 2-3 symptoms. Despite the prevalence of REDs and LEA in athletics, there is a discrepancy in confidence and ability of coaches and physicians to identify athletes with symptoms of REDs and the Female Athlete Triad.
One study shows that less than 50% of healthcare professionals and coaches who work with athletes can identify the Female Athlete Triad components, and in another study involving physicians, only 37% were comfortable identifying and treating the triad. This discrepancy in prevalence and confidence in identifying if an athlete presents with the condition should be addressed by improving education on REDs and LEA in both athletic and medical settings.
Common characteristics in competitive athletes include perfectionism, compulsive behavior with exercise, the ability to push their bodies to the limit, and often in runners there is pressure to be lean or have a certain appearance in order to produce perceived optimal performance. These factors combined together can make runners at risk for obsessive compulsive disorder, eating disorders and disordered eating, and as a result REDs. Runners should look to treat their REDs, but treatment may also include treatment for potential root causes of why REDs occurred. This is why it can be important to approach treatment with a multi-facet health care team.
From a nutritional standpoint, treating REDs often includes eating enough (and plus some, in some cases) to meet daily energy needs. Some treatment plans also include a temporary period of reduction in physical activity in order to allow the athlete to improve their energy availability. Excess physical activity can sometimes blunt the appetite, so reducing physical activity when a period of increasing energy intake is necessary can allow the appetite to return and make the necessary increase in food consumption more feasible. Some studies show that eating more frequently throughout the day through incorporating more meals or snacks, and focusing on calorie dense foods are the most potentially successful strategies to implement when treating REDs. Athletes should also work with a physician and registered dietitian to assess if supplementation of certain nutrients is necessary based on the individual’s unique lab work and past history of potential nutrient deficiencies.
Need support with this? Check out this masterclass that goes over how to understand if you’re eating enough including sample meal plans & troubleshooting common challenges.
References
Logue DM, Madigan SM, Melin A, et al. Low Energy Availability in Athletes 2020: An Updated Narrative Review of Prevalence, Risk, Within-Day Energy Balance, Knowledge, and Impact on Sports Performance. Nutrients. 2020;12(3):835. Published 2020 Mar 20. doi:10.3390/nu12030835
Mountjoy M, Sundgot-Borgen JK, Burke LM, et alIOC consensus statement on relative energy deficiency in sport (RED-S): 2018 updateBritish Journal of Sports Medicine 2018;52:687-697.
Rogers MA, Appaneal RN, Hughes D, Vlahovich N, Waddington G, Burke LM, Drew M. Prevalence of impaired physiological function consistent with Relative Energy Deficiency in Sport (RED-S): an Australian elite and pre-elite cohort. Br J Sports Med. 2021 Jan;55(1):38-45. doi: 10.1136/bjsports-2019-101517. Epub 2020 Nov 16. PMID: 33199358.