The problem associated with being underweight

While being overweight is widely acknowledged a being ‘unhealthy, not as much is said about being underweight. 

The body needs a certain amount of body fat to maintain normal bodily functions, particularly hormone function. Additionally, when energy intake from food is not sufficient, the body may start to break down muscle tissue as fuel for the brain, heart, and lungs. 

Immune health and fertility may be the first things that are effected once someone is underweight as the body must effectively go on ‘power saving mode’= only expending energy on the most essential bodily processes. 

The down regulation of hormones that comes with this ‘energy saving’ can mean that your bones become weaker and may lead to osteoporosis (i.e., low bone density). This greatly increase your risk of bone fracture, which is particularly worrying if you are someone who exercises a lot!

Another factor to consider is the nutrients you are not getting when you are not eating enough. A diet that is low in energy, also tends to be low in nutrients. Our body needs a wide variety of nutrients to function at its best- this is why we need a wide variety of fruits and vegetables (all the colours), along with a variety of wholegrain, lean proteins and heart healthy fats.

As our bodies down-regulate bodily processes that are deemed unnecessary, digestion may become sluggish, and our brains may not function as effectively contributing to poor mental health. Yes, undereating can contribute to mental health conditions such as anxiety and depression. 

While not a perfect measure, the standard measure of being underweight is a Body Mass Index (BMI) below 18.5. Many people though, will experience the negative side effects of being underweight above this BMI. If you are experiencing poor mental, health, sluggish digestion, low energy, low libido, getting sick often or are slow to heal from injuries, consider seeing a dietitian to discuss your diet, as these can all be signs of under fuelling or being underweight.

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About the author

Cheyenne Holman

Cheyenne Holman

Accredited Practicing Dietitian (APD)
Accredited Sports Dietitian
Certified Personal Trainer
Yoga Alliance Certified Yoga Teacher