The Impact of Under-Eating: What Happens When You Eat Less Than Your Body Needs
In today’s era, “eat less” is often taken as the fast track to weight loss for a healthy body. This statement is partially true, while the risks of under-eating often go overlooked. Overeating is not a good idea, nor does undereating. Let’s dive deep into the mystery of understanding what our body needs and why is it important to obtain that.
Undereating
Everyone’s energy requirement is different depending on height, weight, physical activity, metabolism and the list goes on. When you are getting energy less than your body’s requirement, you are considered undereating. Calorie restriction can sometimes be beneficial, but chronically eating too little can be harmful and detrimental on health. In severe case, it can cause life-threatening consequences that is extremely dangerous.
1. Short-term Effects of Undereating
When you first start eating less than your body needs, the effects may seem manageable. However, over time, serious issues can arise. Here’s what can happen when your energy requirements aren’t met:
Fatigue and low in energy
Food is the body’s primary fuel source. When you don’t eat enough, your energy levels drop, making daily tasks and especially physical activity—challenging. Without sufficient calories, even simple activities can feel exhausting [1].
Mood Change
The word “hangry” is the combination of “hungry” and “angry”, and it is not invented without a reason. Studies show that restricting calories by 60% or more could lead to mood problems such as irritability and anxiety. [2] The emotional imbalance is your body’s way of signalling distress and experiencing stress.
Difficulty in Concentrating
Concentration may be impaired while the energy intake is low. Although a lot of under-eaters describe themselves to be more focus and alert in fulfilling their task, it is always unsustainable. The brain is an energy-consuming organ, which takes up about 20% of the body’s energy. When the primary source of energy (glucose) is absent, the function of brain may become sluggish and have impaired memory.
2. Long-Term Effects of Undereating
Chronic undereating can do significant harm to your body’s system. Below show the most common long-term effects of undereating.
Slowed Metabolism
Weight loss is a complicated process which involved a lot of scientific mechanism underneath. Undereating is only beneficial for a calculated amount, which is specific for every individual. When calorie intake is consistently too low, your metabolism slows as the body adapts to conserve energy. This can hinder weight loss efforts and lead to unintended weight gain. [3]
Muscle Loss
Human body is an intellectual creation. When there is negative energy balance, our body will find ways to get their energy to fulfil the energy required, and that’s when muscle loss may be induced. The body will enter the starvation mode and the muscle tissue may be broken down for energy usage. Without adequate protein intake, muscle maintenance becomes even harder. [4]
Nutrient Deficiencies
Calorie is important for energy, so does the other nutrients such as vitamins and minerals. The common deficiencies associated with undereating included but not restricted to:
- Iron
- Iodine
- Calcium
- Vitamin D
- Vitamin B12
Human body does not have the ability to produce minerals and vitamins and have to obtain them from diet. Hence, people with nutrient deficiency can be often seen to have anaemia, weakened bones, hair loss and poor immunity.
3. Disrupted Metabolism
Calorie deficit affects your hormones significantly, impacting everything from metabolism to reproductive health.
Thyroid Dysfunction
Thyroid gland is responsible to produce hormones that regulate your metabolism. Low-calorie intake reduces thyroid hormone production, slowing metabolism. This condition, known as subclinical hypothyroidism. The symptoms include brain fog, depression and anxiety, dry skin and hair, fatigue and unexplained weight gain. [5]
Elevated cortisol
Undereating induces stress, which increases cortisol (stress hormone) production. The ripple effect of raised cortisol may lead to increased fat storage, poor sleep and increased anxiety. [6]
Impaired Insulin Sensitivity
When body is in distressed, blood glucose will be raised in a “fight or flight” reaction. However, in prolonged stress, it will cause the body to adapt and become insensitive to insulin. It significantly increases the risk of developing diabetes. [7]
4. Reproductive Health
Undereating, which leads to undernutrition, can cause major issue in reproductive system, women in particular. Reproductive hormones, particularly estrogen, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), are responsible for regulating menstrual cycle, ovulation and fertility.
Menstrual Irregularity
When calorie intake is too low, gonadotropin-releasing hormone (GnRH) production by hypothalamus will reduce. The reduction of GnRH disrupts the production of Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH), which are responsible for regulating menstrual cycle, ovulation and fertility. Hence, it may lead to irregular or absent periods (amenorrhea) [8].
Reduced Fertility
Low body mass index (BMI) resulted by inadequate fat intake can disrupt the physiological reproductive function and increase the risk of infertility. Low body fat levels can further impact ovulation and conception. [9]
5. Mental Health Consequences
Impact on Stress and Mood
The hormone disruption due to undereating can cause chain reaction to stress and emotional health. Studies have shown that undereating may lower leptin, a hormone that signals satiety, which in turn increases appetite. This can create a vicious cycle of emotional eating and guilt. [10]
Increased Risk of Disordered Eating
Undereating can sometime develop into an eating pattern if it is overdone. When focusing excessively on restricting calories or achieving a “perfect” weight, food and body image may easily become the sources of stress, creating a toxic relationship with food.
Bottom Line:
Striving for health and weight goal is commendable, but undereating without proper and accurate knowledge can backfire. It may lead to unwanted health consequences and concerns. A sustainable health and weight goal should come from balanced, nutrient-rich diet without sacrificing your desire to have some nice food. Your health is about balance, not extremes.
Are you wondering if you are doing the right way to achieve your health and weight goal? Let not keep things ambiguous and assumed. Contact your dietitian at Diet Ideas for personalized advises and meal plans! Discover health, discover life.
Reference:
- Osilla, E.V., Safadi, A.O. and Sharma, S., 2022. Calories. StatPearls, Available at: <https://www.ncbi.nlm.nih.gov/books/NBK499909/> [Accessed 15 November 2024]
- Prvulovic, M., Todorovic, S., Milanovic, D., Jovic, M., Vujovic, P., Kanazir, S. and Mladenovic, A., 2022. Calorie restriction changes the anxiety-like behaviour of ageing male Wistar rats in an onset- and duration-dependent manner. Mechanisms of ageing and development, 204, 111666. https://doi.org/10.1016/j.mad.2022.111666.
- Katzeff, H. L., O’Connell, M., Horton, E. S., Danforth Jr, E., Young, J. B. and Landsberg, L., 1986. Metabolic studies in human obesity during overnutrition and undernutrition: thermogenic and hormonal responses to norepinephrine. Metabolism, 35(2), pp.166-175.
- Janssen, T. A. H., Van Every, D. W., & Phillips and S. M., 2023. The impact and utility of very low-calorie diets: the role of exercise and protein in preserving skeletal muscle mass. Current opinion in clinical nutrition and metabolic care, 26(6), pp.521–527. https://doi.org/10.1097/.
- Peeters, R. P. (2017). Subclinical hypothyroidism. New England Journal of Medicine, 376(26), pp.2556-2565.
- Radahmadi, M., Shadan, F., Karimian, S. M. and Nasimi, A., 2006. Effects of stress on exacerbation of diabetes mellitus, serum glucose and cortisol levels and body weight in rats. Pathophysiology, 13(1), pp.51-55.
- Yaribeygi, H., Maleki, M., Butler, A. E., Jamialahmadi, T. and Sahebkar, A. 2022. Molecular mechanisms linking stress and insulin resistance. EXCLI journal, 21, pp.317–334. https://doi.org/10.17179/excli2021-4382
- Gordon, C.M., Ackerman, K.E., Berga, S.L., Kaplan, J.R., Mastorakos, G., Misra, M., Murad, M.H., Santoro, N.F. and Warren, M.P, 2017. Functional Hypothalamic Amenorrhea: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab, 102(5), pp.1413-1439.
- Łakoma, K., Kukharuk, O. and Śliż, D., 2023. The Influence of Metabolic Factors and Diet on Fertility. Nutrients, 15(5), 1180. https://doi.org/10.3390/nu15051180.
- Mamo, H. I., Louka, P. and Pilafas, G., 2024. The Effect of Attachment Dimensions, Perceived Stress and Specific Perfectionism Dimensions on Emotional Overeating and Emotional Undereating. International Journal of Research and Review, 11(5), pp.456-474.
