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Updated: Nov 11, 2022

Under eating can happen for many reasons. Iit might be because you’re on a diet that avoids foods it deems bad, unhealthy, or too high in calories. It might be that you believe eating an adequate amount of food is overeating, so you try to cut back. It’s really common with the clients we work with to not know that they’re undereating.

This article will give you 5 signs that you’re not eating enough. We think a few of them will shock you. Let’s jump in…

  1. You’re cold

Do you constantly need to layer up because you’re cold? For some, being hungry is signalled by feeling cold. Especially in cases of extreme hunger, where your body hasn’t had enough food in a significant time (e.g. more than an hour.)

Your body can regulate its own temperature by thermoregulation. It’s what has you sweating after exercise or shivering in cold weather - an internal thermostat. And like most of our body’s functions it requires glucose, or sugar, to work. When you don’t eat enough, you don’t have enough glucose to keep this process running properly.

And when you’re not eating enough, your body goes into a little bit of starvation mode. In order to keep you running on lower energy it slows down your metabolism and lowers your body temperature. Think of it as you turning your heating down if you have less money to pay your heating bill. Studies have shown that people who under-eat through dieting actually have a lower body temperature than those who don’t.

The long term dangers of being cold:

  • If you start to experience blue hands and feet you may have long term effects on circulation or nerve functioning if you feel any pins and needles

  • You may start to grow extra fine hair on the face called lanugo, which is grown to try and keep you warm

  • Low levels of thyroid hormones which in turn cause low energy, low mood and a negative effect on your health

How to tell if you’re feeling cold because of hunger:

  • Increase your intake and see if your body temperature starts to go up

  • Note if after you eat you experience feeling warm and drowsy.

  • Notice if when you’re wearing extra layers and applying external heat if you still feel cold

2. Your period is gone or it’s irregular

You might have heard of hypothalamic amenorrhea. It’s the technical term for losing your period.

What constitutes a normal period? What constitutes a ‘normal’ period varies. Periods can be long or short, heavy or light and can last from two to eight days. Over time you may start to see what is ‘normal’ for you, and making a note of symptoms / period length etc. may help you see patterns. There are a lot of apps that can make this a little easier if you forget.

There’s a term called ‘ovarian set point’ which means different women require different amounts of energy in order to ovulate, and have a period. Periods can also be affected by stress, changes in weight, contraception methods, medication use, age, sleep and even travelling across time zones. As you can see a lot of things might be affecting it.

Why have you lost your period? When you don’t get enough overall intake, or a specific macronutrient, then your body thinks you don’t have enough food. It then decides to avoid the risk of getting pregnant if you don’t have enough fuel to make a baby. It switches off signalling that keeps your menstrual cycle running.

Some tips to get your period back:

  • Eating more - sounds simple, but this will help support all your body’s functions. If you’re currently restricting, work to stop the diet. If need be, work with someone to address your relationship with food.

  • Exercising less - frequent exercising that is quite rigorous will put stress on your body. This makes it stop producing reproductive hormones that drive your period. Exercising less, either in frequency or intensity will help signal to your body that it is no longer under stress.

  • Add more fat to your diet - one of the main roles of fat in the diet is to help with your hormones. Oestrogen and progesterone are the hormones that drive your period. Sources include olive oil, nuts, olives, cheese, dairy and eggs.

  • Manage sources of stress in your life - stress affects your hypothalamus - the part of the brain that controls your hormones. Stress reduces its signalling, meaning less ovulation. Managing stress and trying to minimise its effect on your life can reduce its effect on your period.

It’s important to note that it can take up to six months for periods to return to normal after you start to increase your intake again. So you may have to give it some time.

3. You have really low mood

This can be depression and feeling low or being easily irritated. Hangry is a controversial term but is often used when you snap at those around you when you’ve under-eaten.

The nutrients from our food affect the brain, especially the emotional centre. Serotonin, sometimes known as the happy hormone, is drastically reduced as it is synthesised from our diet. People suffering from anorexia have been found to have significantly lower levels of serotonin than those not suffering from an eating disorder. And low levels have been associated with depression and low mood.

There’s a strong link between eating disorders and low mood, whether you’re restricting, purging or binging. Between 50 and 75% of those struggling with an eating disorder are said to experience symptoms of depression.

Notice when you are experiencing low mood or irritability - is there a crossover between these and periods of not eating?

How to improve low mood caused by undereating:

  • Slowly increase the amount you’re eating

  • Re-introduce food groups you may have been cutting out

  • Work with a professional if low mood persists

  • Tap into your social network

4. You're constantly thinking about food

We’ve written a post about food obsession that you can read here - in it we detail how restricting can make our brains ‘obsessed’ with food. Food obsession is a sign that your body is being deprived of vital nutrients.

Dieting is technically semi-starvation for the body. We have a whole post on the Minnesota Starvation Experiment which showed that undereating to the point of starvation causes obsessive thoughts about food, which only cease when food intake is increased.

It may also be worth thinking about why you might be undereating - if you are purposely restricting this will have its own effect on your brain. You’re telling yourself you can’t have something, making you crave it. Not only are you physically experiencing semi-starvation but your brain is doing mental acrobatics as to what constitutes ‘good’ or ‘bad’ foods and what / how much you should be eating. It’s no wonder this takes up a lot of brain space, especially given your reduced brain capacity when underfuelled.

How to stop your constant thinking about food:

  • Eat safe foods - if it's easiest to eat foods that are ‘safe’ to you. Foods that you feel comfortable eating, even if you’re dieting or only eating certain types of food. Once you’re sufficiently fuelled you can take steps to increase foods that are considered safe.

  • Eat with others - this allows you to focus on the company and conversation more than what you’re consuming. If you’re struggling to eat enough, maybe confide in a friend who can help support you to eat more.

  • Distract yourself after meals - especially if you find yourself dwelling on food after meals. How much you’ve eaten, and any negative feelings of guilt. Find things that distract or interest you, whether that’s chatting to friends / family or something you do alone.

  • Eat more - maybe start increasing your intake slowly, and see how it feels. Especially if you’ve been restricting for a while.

5. You’re experiencing digestive issues like bloating

Undereating slows down your metabolism, and so food moves slowly through your digestive tract. This might mean you feel fuller or bloated. A lot of individuals with disordered eating or eating disorders report symptoms such as constipation, diarrhoea, bloating, cramping, pain in the abdomen and reflux.

If you’re someone who skips breakfast, your stomach will start to create gas and bloating might occur because you have nothing to digest. When you then eat you’d be more likely to eat a large volume of food, which furthers the bloating. This cycle of restricting and overeating will exacerbate any stomach issues.

If you’re undereating as part of a diet it may be that you’re cutting out entire food groups. This means your food intake isn’t so varied, and the amount of ‘good bacteria’ in your gut will decrease. This means if your intake increases again you might experience increased bloating. This will subside with increased food intake, especially eating a variety of foods.

Restricting food intake, periods of binging, avoiding whole food groups, and purging via either vomiting or using laxatives can all cause digestive issues. Whether you’re experiencing an eating disorder or just the effects of restricting as part of a diet it can have long term effects if restricting over a long period of time.

Some of the long term effects of these issues:

  • Electrolyte imbalances - electrolytes are used in muscle and nerve function. If you experience digestive issues that can lead to constipation or diarrhoea it may affect your electrolytes.

  • Lazy Bowel Syndrome - also known as sluggish bowel or slow gut. This is when your bowel movements are slow and sometimes painful, often with constipation. Restriction / undereating can cause bowel related reflexes to become weaker and digestion slowed.

  • Heartburn - undereating can cause stomach acid to aggravate your stomach. We have an article on heartburn and its effects which can be read here.

  • Social effects - if you’re constantly bloated or uncomfortably full it can affect how you feel socialising and being with others.

Starter ways to deal with your digestive problems:

  • Check in on your fibre - fibre helps reduce the chances of constipation. Think of leafy greens, kale and spinach. If you’re currently not eating any of these try and up your intake but if your diet is full of these - think raw food diet - then it may be best to cut back a little. A note here: Sometimes adding fibre will make gut symptoms worse. We recommend reaching out for 1:1 support with us to navigate your gut symptoms.

  • If you’ve been restricting for a long period of time consider working with a professional to help you increase your intake.

  • Avoid taking laxatives if you experience constipation, or use them sparingly. We have an article on why here.

We hope that this list has helped shine some light on what you might be experiencing. Just know you’re not alone - many people wonder why they’re experiencing the symptoms they are before realising they’re undereating. In today’s 24/7 go go go culture it can be easy to miss meals or undereat accidentally.

And if you find that eating more seems like too much of an uphill battle then maybe working with a professional is your best bet. We’ve worked with a range of people just like you.



We are a specialist eating disorders and disordered eating online clinic. We support people with troubled relationships to food with expert Nutrition Counselling.

Founded by Shannon Western in 2019. The team has grown to welcome wonderful Dietitians and Nutritionists all to help you feel better with food.

Are you:

  • Struggling with feeling overwhelmed or out of control with eating?

  • Unsure about when, why, and how much to eat?

  • Ready to take the steps (however small!) away from your eating disorder, disordered eating, or long dieting history?

We are here to help you do just this (and more). All with compassionate, practical, supportive person-centred Nutrition Counselling.

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