The Effects of Underfueling
Underfueling, or not providing adequate energy for the body, can lead to a variety of health problems long-term. Side effects that may occur include the reduction of reproductive hormones, bone density loss, and poor heart health (1). These effects can in turn lead to decreased athletic performance and higher risk of injury. This blog post will discuss the various effects underfueling on health to emphasize the importance of getting enough food throughout the day is for optimal performance and health.
How does Underfueling Occur?
Underfueling can occur unintentionally or intentionally (3).
- Unintentional underfueling can be due to hunger signals being absent soon after exercise and due to external stressors of life. When stressors arise, your body’s main priority is to focus on addressing the source of stress and signals to eat or digest food will diminish. This causes your hunger cues to go on the back burner until the stressors are dealt with. In these instances, individuals may not recognize that their body needs nourishment.
- Underfueling can be caused intentionally as a result of disordered eating and eating disorders. There are red flags to watch for that signal disordered eating is present. These red flags are discussed in a previous blog post titled “Identifying Disordered Eating Patterns.” Some of the red flags include:
- Labeling foods as “good” or “bad”
- Labeling foods as “good” or “bad” can lead to underfueling by not allowing all foods to be permissible. The “bad” foods category may consist of foods that actually promote recovery or pre-workout fuel (such as bagels, granola, protein bars, or milk). Restricting the diet to avoid these foods can lead to underconsumption of essential nutrients, which can then lead to lowers levels of endurance, excessive soreness, and increased risk of illness or injury.
- Obsession with food, exercise, and/or body image that negatively impacts an individual’s quality of life
- Similar to the previous red flag of disordered eating, this can lead to underfueling because an individual may restrict the foods they eat to maintain a certain body size, which can lead to eating less than the body needs.
- Being anxious around food in social environments
- Being anxious around food in social situations can lead to an individual carefully selecting amounts and types of foods that appear to be “acceptable” by the people at the social event. This can lead the individual to underfueling if the individual eats less than their body needs.
- Labeling foods as “good” or “bad”
What Areas of Health are Affected by Underfueling?
Bones are critical to performance and overall health. Bones support many functions and abilities in your body, such as storing calcium. By not providing your bones with enough nourishment, the following can occur:
- Decreased bone density
- Impaired performance
- Increased risk of stress fractures and injuries (1,2)
Estrogen is an important hormone for bone health (1). Estrogen levels are low when undernourished, which leads to a reduction in the creation of new bone. More bone is reabsorbed than created, further reducing bone density (1). Unfortunately, bone density cannot be completely reversed at a certain point (1). For this reason, it is crucial to consume adequate nourishment for your bone health, such as calcium and protein.
- Not getting enough fuel can greatly impact bone health, and put an athlete at a higher risk for injury.
Loss of Menstrual Cycle
In addition to bone health, estrogen plays an important role in menstrual cycle regularity for female athletes. Although not always the case, the complete loss of the menstrual cycle can occur with underfueling. Low estrogen levels can lead to amenorrhea (1). Amenorrhea is defined as the loss of menstrual cycles for 3 months, having less than 9 cycles a year, or not having a menstrual cycle start by age 15 (1,4).
- Loss of estrogen contributes to the loss of menstrual cycle, and bone health.
Underfueling also reduces testosterone levels in the body (1). Testosterone, like estrogen, can impair bone health and may do so faster than estrogen can (1).
- Poor bone health can lead to increased instances of injury.
Metabolism is the process of converting food into energy to support all daily activities. When you are not giving your body enough nourishment, your metabolism decreases to preserve energy (1). This leads to less energy availability for the function of some organs and biological processes, such as digestion, heart rate, blood flow to hands and feet, and overall energy levels (1). This also means that our body does not have the fuel it needs for optimal athletic performance because our organs and biological processes don’t occur at their normal rate.
- Low metabolism leads to biological processes not occurring at their normal rate, so an individual is unable to perform at their best.
As a result of a reduced metabolism, digestive symptoms can occur, such as bloating, cramping, or constipation. The digestive system slows down because the body already has to keep many other systems of the body operating at a normal rate (1). This can in turn alter your bowel movements and stool consistency (1).
- Constipation can make it harder to perform and concentrate.
The cardiovascular system includes your heart and blood vessels. Because athletes exert a lot of energy while exercising, when an athlete gets up and takes a short walk their heart rate does not typically increase drastically (1). In prolonged underfueling, cardiac muscle may be degraded, which causes the heart to have to beat faster to deliver the same amount of blood to various tissues. This can lead to irreguluar heart rythems and, in extreme cases, a heart attack (1).
- The cardiovascular system has to work harder, reducing optimal performance.
Skin, Hair, and Nails
Our skin, hair, and nails do a wonderful job of informing us when our body isn’t fueled. When undernourished:
- The skin will become dry and lose its youthful appearance (1)
- Nails become brittle and stop growing at their normal rate (1)
- Hair loss and hair thinning can occur (1)
There are several nutrients important for skin, hair, nail health. Some of these nutrients include protein, iron, biotin (one of the B vitamins), omega-3 fatty acids, and Vitamins A, D, and E (5).
- Inadequate intake of protein and other nutrients has an impact on hair, skin, and nails. Changes to these tissues is a way for your body to signal that you are not receiving enough of one or more of these nutrients, many of which are vital for optimal performance and immune function.
Underfueling negatively impacts mental health (2). Food has an important role in fueling our physical body, which also includes the systems that affect mental health. Our gut and brain are connected, so if the body isn’t fueled enough, mood and stress levels can be affected. For example, 90% of the neurotransmitter serotonin is found in the gut. Serotonin helps to regulate our mood, appetite, and sleep cycle (6).
Carbohydrates are critical to brain health as well, as they are the body’s main source of fuel! If you ever experienced feeling “hangry”, part of this feeling is a result of blood glucose levels getting too low as a result of inadequate carbohydrate intake.
Finally, and individual’s relationship with food can affect mental health as well. If you find yourself constantly thinking about food and judging your self-worth based on your food choices, you may experience higher rates of anxiety or depressive symptoms. Learning to feel comfortable with eating a wide variety of foods in a variety of different social situations will help to create a healthy relationship with food and improve mental health.
- Underfueling can be caused intentionally (disordered eating) and unintentionally (not eating after working out because of not feeling hungry).
- Underfueling can lead to many negative effects on the body, which can, in turn, lead to poor athletic performance and overall health.
- It is important to make sure you have a healthy relationship with food to help optimize performance and find enjoyment in food.
To learn more about underfueling, check out these resources:
- Gaudiani JL. Sick Enough. A Guide to the Medical Complications of Eating Disorders. Taylor & Francis; 2019.
- Ackerman KE, Holtzman B, Cooper KM, et al. Low energy availability surrogates correlate with health and performance consequences of relative energy deficiency in sport. Br J Sports Med. 2019;53(10):628-634. doi: http://dx.doi.org/10.1136/bjsports-2017-098958.
- Gaitley, J. Identifying Low Energy Availability in Female Athletes. Phoenix Children’s. Published August 5, 2020. Accessed April 21, 2021. https://www.phoenixchildrens.org/blog/2020/08/identifying-low-energy-availability-female-athletes
- The Practice Committee of the American Society for Reproductive Medicine. Current evaluation of amenorrhea. The Practice Committee of the American Society for Reproductive Medicine. Published November 2008. Accessed April 22, 2021. https://www.asrm.org/globalassets/asrm/asrm-content/news-and-publications/practice-guidelines/for-non-members/current_evaluation_of_amenorrhea.pdf
- Wright, KC. The Growing Field of Nutritional Psychiatry. Today’s Dietitian. Published July 2019. Accessed April 22, 2021. https://www.todaysdietitian.com/newarchives/0916p56.shtml
- Reisdorf, AG.CPE Monthly: Beauty and Nutrition — Evidence-Based Dietary Practices Can Help Patients Look and Feel Their Best. Today’s Dietitian. Published September 2016. Accessed April 22, 2021. https://www.todaysdietitian.com/newarchives/0719p10.shtml
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