The Impacts of Chronic Undereating

Sep 8, 2022


Would you be surprised to hear that the #1 problem we frequently identify with nutrition clients is under-eating?

Most individuals are aware of the risks of over-eating for extended periods of time (weight gain, chronic disease, reduced lifespan, etc.). The diet industry ensures that we are constantly reminded of these risks, while social media reinforces the message to eat less by promoting weight loss supplements and the latest fad diets using images of people and their "transformations" that are so far from reality.

These social and environmental influences can have lasting health impacts, from both a physical and mental standpoint. When attempting to change how you eat, whether that be for weight loss, training or health purposes, it is important to understand the potential impacts of everything you may be implementing, so you can then develop a well-rounded and balanced plan of action that best fits every aspect of your life. Sustainability is the key to making lasting and beneficial changes to your nutrition.

While the exact impacts of under-eating depend on the degree and extent of the diet, as well as many other biological factors, there are frequent commonalities experienced among those who don't eat enough for long periods of time (>1 year). Low energy, mood, and brain fog may be the most common symptoms, as the brain sends signals to the body to slow down when it detects that you are not eating enough. 


It's usually pretty obvious that you'll have low energy levels if you don't eat enough, but are you aware of the other impacts it can have on your health?

  • Digestion
    • When the brain tells the body to slow down, that includes digestion
    • When digestion is slowed, food remains in the G.I. tract longer
    • This leads to a heightened sense of fullness or bloating, which is not only uncomfortable and at times painful, but can also mislead some to believe they have food allergies or intolerances
    • Due to this misconception, some individuals may find themselves unnecessarily cutting out certain foods and eating even less as a result
  • Metabolism
    • Our bodies are always working towards homeostasis, or the condition in which all our internal processes are stable and functioning at their pre-set limits (ex: body temperature)
    • In an attempt to preserve energy when under-eating, the brain sends signals to the thyroid to slow down its production of the hormones that assist in regulating our metabolism
    • As a result, metabolic rate decreases
  • Stress & Sleep
    • Our bodies perceive under-eating as a form of stress
    • Our adrenals then respond to this stress by ramping up cortisol production
    • When cortisol levels are high, we tend to experience a general feeling of restlessness and sometimes anxiousness
    • Sleep is disrupted as a result, and various other health risks then come into play such as high blood sugar, diabetes, heart disease, cancer, memory loss, etc.
    • Learn more about the impacts of chronic stress here
  • Reproduction 
    • Sex hormone production is impaired when we don't eat enough
    • When the production of our sex hormones is inadequate, we experience a reduced sex drive 
    • Our bodies also determine that it's not safe to procreate, as a result we then experience infertility


So, how much should you be eating to avoid these potential risks? This body weight planner provided by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) is a great tool to establish a base understanding of your energy and calorie needs based on your activity levels. If you're in need of additional guidance, book a free intro session to consult with one of our registered dietitians on what your next steps should be.