February 22, 2022

10 Symptoms of Not Eating Enough: The Dangers of Malnutrition

Table of Contents

Are you eating enough?

You may not be if you are experiencing any of the following symptoms. Not getting enough calories and nutrients consistently can lead to malnutrition. Malnutrition can have serious consequences for your health, including significant chronic fatigue, hair loss, and a weakened immune system. In this blog post, we will discuss the 10 most common symptoms of not eating enough. If any of these symptoms seem familiar to you, it might be a signal that you are not eating enough to meet your nutritional needs. 


Common Symptoms of Not Eating Enough

   1. Chronic Fatigue:

Chronic fatigue is one of the most common physical signs you’re not eating enough. When you don’t get sufficient nutrients, your body doesn’t have the energy to function properly. This can cause you to feel tired all the time, no matter how much sleep you get.


According to the (1) Dietary Guidelines for Americans 2020-2025, an average American adult needs to consume approximately ~2000 calories a day in order to meet estimated nutritional needs. The amount of calories needed for each person varies, depending on age, gender and activity level. Also, this is a guideline and not an outright caloric prescription. 


Calories are important because they provide energy for your body’s daily functions such as breathing, thinking and moving around. Symptoms of not eating enough can start with a general feeling of low energy and fatigue.


The constant pressure people feel to reduce their caloric intake may lead them to blindly restricting vital nutrients we need to function properly. Consistent under consumption of these nutrients may result in malnutrition, something we take very seriously here at Nutriving.

   2. Irritability: 

Feeling irritable and moody is another common symptom of poor caloric intake. Low blood sugar can definitely lead to irritability. We have some pretty killer episodes on sugary treats, snacking, and fruit sugar on our podcast, Dietitians Uncorked. We get into the “hangrys” and how to avoid them. 


When you’re feeling low on energy, you might easily become frustrated or angered. You might also find that you’re more emotional than usual. There have been (2,3) several studies that link mood disorders to restrictive dieting patterns. 


Symptoms of not eating enough, like irritability, may be the more obvious one when interacting with others. If you find yourself feeling consistently more irritable, this may be related to your nutrient intake. 


   3. Brain Fog: 

Suffering from brain fog is another sign that you may not be eating enough. Brain fog refers to feelings of confusion, forgetfulness, and difficulty concentrating.

You know those times that you feel like it’s really hard to concentrate? You seem to forget literally everything? Being productive becomes very hard? This is brain fog. 

When the body doesn’t have enough energy, it can’t function properly. This includes the brain, which can’t function at its full capacity when it’s not getting enough energy. 


It’s SO important to make sure you’re eating enough food every day so that your body has the energy it needs to function well. If you feel like you might be experiencing brain fog, ask yourself when was the last time you ate? Do you need a snack? 


The (4) MIND diet, one of the dietary patterns that supports brain function and the prevention of dementia, recommends regularly eating dark leafy greens, berries, beans, seafood, whole grains, and nuts. Snacks for brain fog anyone?


Ps: We talk about this during our 1:1 sessions via our Personalized Nutrition Analysis.


   4. Depression: 

Depression and malnutrition have been shown to be correlated. These two give “chicken-and-egg” vibes. Regardless of which one comes first, it is fair to say that a malnourished individuals will not have optimal cognitive function. 


As it is common among elderly patients, changes in appetite or swallowing ability may affect their overall nutrient intake. In a (5) study that focused on elderly rural patients, researchers concluded that depression was a major  risk of malnutrition. Another study (6) with a similar patient population concluded that malnutrition was significantly correlated with the diagnosis of depression. 


It is no surprise to us that malnutrition plays a role in depression. The proper function of our brain, hormones, and cognitive ability depend on a nutritionally sound diet. 


   5. Weakened Immune System: 

A weakened immune system is one of the physical signs you’re not eating enough. When the body doesn’t have enough nutrients, it can’t fight off infections and diseases as well as it should. This can make you more susceptible to illness and infection (7).


 Additionally, if malnutrition is present, it can slow down the healing process. This often relates to inadequate protein-energy intake as protein aids in the repair of muscle mass and skin tissue (8). 

Are you constantly fighting a cold you can’t seem to shake off? Do you have a minor wound that simply won’t heal? These are clear symptoms of not eating enough protein, vitamins, and minerals!


Another very important reason why consuming adequate amounts of calories is the fact that we are still fighting a global pandemic. A viral global pandemic! We, collectively, need everyone’s immune system to be at the top of their game. Let’s not forget the role that nutrition plays here. 



   6. Hair Loss: 

As you can already tell, eating a balanced diet is imperative for our bodies to function well. It’s hard to underestimate the importance of eating enough. When you don’t get the nutrients, vitamins and minerals your body needs, it can lead to an array of unpleasant symptoms.


Another physical sign you’re not eating enough is hair loss. Hair loss is one of many symptoms that can be caused by changes in caloric intake and malnutrition. Hair loss, particularly, can be associated with inadequate protein intake, biotin deficiency, iron deficiency, and/or zinc deficiency (9,10,11) .

Hair can also get coarse and “corkscrew-like” when there is a deficiency in vitamin C (12). 


I have spoken about this in other blogs and in our podcast. Our culture puts an overt emphasis on aesthetics and nutrition. Nutrition assessments have everything to do with overall health status and health outcomes, not aesthetics. 


However, if the way we convince people to eat vegetables and fruits is via the aesthetics appeal, then hair is something to pay attention to. Inadequate caloric intake can lead to hair loss. 

   7. Dizziness:

Dizziness is a sensation of unsteadiness or lightheadedness. It can be caused by a variety of factors, including low blood sugar, dehydration, and medication side effects. Dizziness can also be one of the symptoms of not eating enough. 


Besides low blood sugar, we must take note that dizziness is also a common sign of dehydration. All of our clients know that hydration is a part of a healthy balanced diet. We think it’s SO important that we added it to our curriculum of our Group Program


We also created a quiz on dehydration because not everyone knows the tell-tell signs of dehydration. Give it a try if you suspect you might be dehydrated. 

   8. Amenorrhea:

Amenorrhea is the absence of a menstrual period. It can be caused by a variety of factors, including hormonal imbalance, stress, and malnutrition. Not consuming enough food can lead to amenorrhea, usually referred as secondary amenorrhea (13).


When the body doesn’t have enough nutrients, it can’t produce the hormones it needs to regulate the menstrual cycle. This can lead to a lack of periods or irregular periods. Overtime, this calorie deficit may lead to an underweight status causing amenorrhea to occur.

If you are curious if you meet the criteria for underweight classification, check out this Woman’s Health link for more information.  


   9. Sleeping Problems:

Sleep disorders can seem like one of the odd symptoms of not eating enough, however, it totally makes sense! 

In a research study, young participants reported poor sleep quality while following a restrictive eating pattern (14). In a different study, women who followed a caloric deficit meal pattern reported poor quality sleep (15).


Tryptophan, a naturally occurring amino acid found primarily in protein, plays an important role as a neurotransmitter that helps sleep cycles. If we are limiting our protein intake, we are also affecting the function of this important neurotransmitter. 


   10. Constipation: 


Constipation can also be one of the physical signs you’re not eating enough. When I worked in an in-patient hospital, the dietitians and I used to say, “everything that goes in, has to come out.” Some of our patients who had poor nutritional intake would complain of constipation due to these changes in eating patterns. 

Constipation, or infrequent bowel movements, makes complete sense since we are not consuming enough food in the frequency we used to. 

In a large study involving college women, individuals who followed the strictest diets with the lowest caloric intake, experienced GI related issues, including constipation (16). 



Consuming adequate calories and nutrients is essential for our overall health and the proper functioning of our body. We can’t expect to function perfectly well when basic nutrients are not being consumed. These symptoms of not eating enough can prompt us to take a deeper look into our dietary patterns. 

Continued inadequate nutritional intake puts us at risk of malnutrition- a condition that affects our entire body!

As a dietitian, I care that you eat enough so that you don’t suffer some of these physical symptoms that can really disrupt your health. Malnutrition is no joke. 


If you’re not sure whether you are meeting your nutritional needs, make an appointment with a dietitian! Your health is important. 




    1. U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition. December 2020. Available at DietaryGuidelines.gov.
    2. Hagan MM, Tomaka J, Moss DE. Relation of Dieting in College and High School Students to Symptoms Associated with Semi-starvation. J Health Psychol. 2000 Jan;5(1):7-15. doi: 10.1177/135910530000500105. PMID: 22048819.
    3. Kalm LM, Semba RD. They starved so that others be better fed: remembering Ancel Keys and the Minnesota experiment. J Nutr. 2005 Jun;135(6):1347-52. doi: 10.1093/jn/135.6.1347. PMID: 15930436.
    4. Morris, MC, Tangney, CC, Wang, Y, Sacks, FM, Barnes, LL, Bennett, DA, Aggarwal, NT. MIND diet slows cognitive decline with aging. Alzheimers Dement. 2015 September; 11(9): 1015-1022. Doi: 10.1016/j.jalz.2015.04.011.
    5. Vafaei Z, Mokhtari H, Sadooghi Z, Meamar R, Chitsaz A, Moeini M. Malnutrition is associated with depression in rural elderly population. J Res Med Sci. 2013;18(Suppl 1):S15-S19.
    6. Islam, M. Z., Disu, T. R., Farjana, S., & Rahman, M. M. (2021). Malnutrition and other risk factors of geriatric depression: a community-based comparative cross-sectional study in older adults in rural Bangladesh. BMC geriatrics, 21(1), 572. https://doi.org/10.1186/s12877-021-02535-w
    7. Bourke, C. D., Berkley, J. A., & Prendergast, A. J. (2016). Immune Dysfunction as a Cause and Consequence of Malnutrition. Trends in immunology, 37(6), 386–398. https://doi.org/10.1016/j.it.2016.04.003
    8. Collins, Nancy PhD, RD, LD/N Protein and Wound Healing, Advances in Skin & Wound Care: November 2001 – Volume 14 – Issue 6 – p 288-289
    9. Mutevelić-Arslanagić N. Utjecaj nutritivne deficitarnosti na status korjena dlake (trihogram) [The effect of nutritional deficiency on hair roots (trichogram)]. Med Arh. 1994;48(2):57-9. Croatian. PMID: 7967790.
    10. Zempleni J, Hassan YI, Wijeratne SS. Biotin and biotinidase deficiency. Expert Rev Endocrinol Metab. 2008 Nov 1;3(6):715-724. doi: 10.1586/17446651.3.6.715. PMID: 19727438; PMCID: PMC2726758.
    11. Deloche C, Bastien P, Chadoutaud S, Galan P, Bertrais S, Hercberg S, de Lacharrière O. Low iron stores: a risk factor for excessive hair loss in non-menopausal women. Eur J Dermatol. 2007 Nov-Dec;17(6):507-12. doi: 10.1684/ejd.2007.0265. Epub 2007 Oct 19. PMID: 17951130.
    12. Esper DH. Utilization of nutrition-focused physical assessment in identifying micronutrient deficiencies. Nutr Clin Pract. 2015 Apr;30(2):194-202. doi: 10.1177/0884533615573054. PMID: 25829342.
    13. (Ame) American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), American Psychiatric Association, Arlington, VA 2013.
    14. Evans L, Kennedy GA, Wertheim EH. An examination of the association between eating problems, negative mood, weight and sleeping quality in young women and men. Eat Weight Disord. 2005 Dec;10(4):245-50. doi: 10.1007/BF03327491. PMID: 16755168.
    15. Karklin A, Driver HS, Buffenstein R. Restricted energy intake affects nocturnal body temperature and sleep patterns. Am J Clin Nutr. 1994 Feb;59(2):346-9. doi: 10.1093/ajcn/59.2.346. PMID: 8310984.
    16. Krahn D, Kurth C, Nairn K, Redmond L, Drewnowski A, Gomberg E. Dieting severity and gastrointestinal symptoms in college women. J Am Coll Health. 1996 Sep;45(2):67-71. doi: 10.1080/07448481.1996.9936864. PMID: 8908880.




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I am a Registered Dietitian (RD) based in Chicago, IL. I have worked in various clinical settings including dialysis, ICU, and NICU. I am bilingual and love my Spanglish speaking peeps!


  1. Lisa Bell March 22, 2022 at 12:51 pm - Reply

    Great article, Cat!

    • Catalina Ruz Gatica, MS, RDN, LDN March 28, 2022 at 12:12 pm - Reply

      Thanks! Glad you enjoyed it!

  2. https://israel-lady.co.il/ August 28, 2022 at 7:34 pm - Reply

    5 stars
    An intriguing discussion is definitely worth comment. I think that you should publish more about this topic, it might not be a taboo subject but generally people do not speak about these subjects. To the next! All the best!!

    • Kelly Wagner, MS, RD, LDN August 31, 2022 at 10:08 pm - Reply

      Thanks for reading!

  3. Warren January 12, 2023 at 12:33 pm - Reply

    Great Information! Thank you such detailed explaination. The most ignored symptom is being moody or Irritability. Many people does not consider it as a problem or may think that will get over it, or hear many things “you will get over it/ overcome it” etc. Not consuming the proper intake can also lead to many other problems like not gaining muscles, feeling lonely, etc.

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