Ever wonder if you’re eating enough? Listen to your body. There are usually physical signs of not eating enough, like constant hunger or irritability.

Achieving and maintaining a healthy weight for your body can be challenging, especially in a society where food is constantly available.

But not getting enough calories can also be a concern — whether it’s due to intentional food restriction, decreased appetite, or other reasons.

In fact, undereating on a regular basis can lead to a number of mental, physical, and emotional health issues. We dive into 11 signs that you may not be eating enough.

To evaluate your weight, you may want to start with your body mass index (BMI). The National Heart, Lung, and Blood Institute provides a chart showing BMIs based on your weight and height.

That said, BMI doesn’t take into account many factors that affect weight, which can vary from person to person.

According to the Centers for Disease Control and Prevention (CDC), the average weight and height of adults over the age of 20 are as follows:

SexHeight (inches)Weight (pounds)Waist circumference (inches)
Males assigned at birth (MAAB)69 inches199.8 lb40.5 inches
Females assigned at birth (FAAB)63.5 inches170.8 lb38.7 inches

Still, researchers have determined that a waist circumference equal to or less than 80–90 centimeters (cm) or 31–35 inches is considered “normal.”

However, these normal values were developed to apply only to white adults. The researchers cite alternative research that was developed to represent African American adults. These values were 76–78 cm or 29–30 inches.

With this research in mind, the average waist circumference values of American adults are actually too high.

So how do you know if you haven’t eaten enough?

If you’re significantly below any of the above values, it may mean you’re considered underweight. Anything above these values increases a person’s chances of developing various health problems, such as heart disease.

That said, being underweight doesn’t necessarily mean you’re not eating enough.

There are other reasons for excessive weight loss, such as heavy exercise, malabsorption, or other underlying health conditions. Reaching out to a doctor is the best way to determine whether you’re eating enough for your body’s needs.


You might be considered underweight if your BMI or weight is too low, according to national guidelines. But there are many factors that influence weight, and this doesn’t necessarily mean you’re not eating enough.

When you don’t get enough calories, you’ll likely feel tired most of the time.

On average, people assigned female at birth (AFAB) should eat about 2,000 calories a day for weight maintenance and 1,500 for weight loss. People assigned male at birth (AMAB) should eat around 2,500 calories a day or 2,000 for weight loss.

These values are just averages and can differ depending on your sex, age, and level of exercise.

The 2020–2025 Dietary Guidelines for Americans provide a full breakdown. You can also learn how many calories are in a pound of body fat.

If you’re consuming fewer calories than the lower limits, you might not be eating enough to sustain your energy throughout the day.


Calories from food give us energy. Eating too few calories can lead to fatigue due to insufficient energy.

3. Hair loss

If you’re noticing an increased amount of hair accumulating in your hairbrush or shower drain, it may be a sign that you’re not eating enough or that you’re not getting enough important nutrients.

An inadequate intake of calories, protein, biotin, iron, and other nutrients is a common cause of hair loss.


Hair loss can sometimes happen if you’re not getting enough calories, protein, and other nutrients.

4. Changes in hunger cues

Being hungry all the time is one obvious sign that you’re not eating enough food, but it isn’t the only one.

Appetite and food cravings can increase in response to drastic calorie restriction. This is due to changes in levels of hormones that control hunger and fullness.

For example, in a 2016 study following mice for 3 months, they were fed a diet containing 40% fewer calories than usual. Researchers found that levels of the appetite-suppressing hormones leptin and IGF-1 decreased in the mice while hunger signals increased significantly.

A 2021 study examining calorie restriction in humans found that restricting calories didn’t lead to a notable decrease in hunger or appetite. But it also didn’t lead to increased hunger or appetite in people who had a low appetite to begin with.

More research is needed to understand how reducing calories may affect hunger and appetite in humans.

What’s more, fasting has been shown to increase the production of cortisol, a stress hormone that has been linked to hunger and increased belly fat.

However, while calorie deprivation may have a hunger-increasing effect in some cases, 2019 research suggests that calorie deprivation over a long time may actually make you feel less hungry and reduce food cravings.


Undereating can cause hormonal changes that increase your hunger in order to make up for missing calories and nutrients. However, in the long term, you may start to feel less hunger and have fewer food cravings.

5. Problems trying to get pregnant

Undereating may interfere with someone’s ability to become pregnant.

The hypothalamus helps maintain your hormonal balance, including reproductive health. It receives signals from your body that let it know when hormone levels need to be adjusted.

Based on the signals it receives, the hypothalamus produces hormones that either stimulate or inhibit the production of estrogen, progesterone, and other hormones.

Research from 2021 suggests that this complex system is highly sensitive to changes in calorie intake and weight.

When your calorie intake or body fat percentage drops too low, these signals may become impaired, leading to changes in the number of hormones released.

Without the proper balance of reproductive hormones, pregnancy cannot take place. Amenorrhea — the medical term for no menstrual period for 6 months or longer — can be a sign of a reproductive hormone imbalance. If you haven’t had a period in 3 months or longer, you should see your doctor for an evaluation.

If you are trying to conceive, make sure to consume a balanced diet with a good amount of calories for your body. This will help your hormones function properly and improve your chances of a healthy pregnancy.


Consuming too few calories can disrupt reproductive hormone signals, leading to challenges in getting pregnant.

If little things have begun to set you off, it could be related to not eating enough.

Irritability was one of several issues experienced by young men who underwent extreme calorie restriction as part of the Minnesota Starvation Experiment during World War II.

Research on mice has found that restricting calories by 60% or more could lead to various adverse effects, including irritability and other mood problems.

According to a 2023 study on mice with obesity, calorie deprivation may increase anxiety behaviors.

On the other hand, animal research from 2018 suggests that eating less may actually have an antidepressive effect.

So far, research on this topic has been conflicting and focused mainly on animals, so more research is needed to understand whether these same effects will occur in humans.

All that said, what affects our moods in terms of nutrition might be how much we eat and what we eat.

For instance, following the Mediterranean diet has been shown to reduce markers of inflammation, whereas eating high calorie foods containing unhealthy fats may actually inflame the immune system. This could affect mood and well-being.


Not getting enough calories and restrictive eating patterns have been linked to irritability and anxiety in some research, but it has been limited. More research on humans is necessary.

If you constantly feel cold, not eating enough food could be the cause.

Your body needs to burn a certain number of calories in order to create heat and maintain a healthy, comfortable body temperature.

Calorie restriction can lead to lower core body temperature. Overall, the more severely you slash calories, the colder you’re likely to feel.


Consuming too few calories can lead to a decrease in body temperature, as you need calories to create heat.

Infrequent bowel movements may be related to low calorie intake. This isn’t surprising since consuming very little food will result in less waste in your digestive tract.

Constipation is typically described as having fewer than three bowel movements per week or having small, hard stools that are difficult to pass. It’s very common in older adults and can be worsened by poor diet.

Research from 2022 suggests that eating fewer calories may be associated with a greater chance of constipation in women, and eating within the recommended calorie range can help reduce the chance of constipation in men.

The researchers also cite an older study suggesting that eating enough can reduce the chance of constipation in children as well.

If you’re having problems with bowel regularity, it’s important to take a look at the amount of food you’re eating and evaluate whether you’re getting enough.


Not getting enough calories may be associated with constipation in women. This is partly due to less waste product in general, but also slower movement of food through the digestive tract.

Research from 2016 has shown a relationship between eating fewer calories and immune system dysfunction.

This means that if you’re frequently sick, you might not be getting enough nutrients that are necessary for healthy immune system function.

Nutrients that are important for immune functioning include certain amino acids — arginine and tryptophan — as well as the following minerals and vitamins:


If you’re frequently getting sick, it may be related to undereating. Contact a doctor to determine if this is the cause or if something else might be affecting your immune system.

Children and adolescents who are not growing as expected might not be eating enough. In younger children, this is known as failure to thrive or delayed growth.

How much they eat and what they eat can influence growth hormones and cause them not to work properly, which can result in stunted growth.

The CDC provides growth charts showing the average expected weight and height of children from ages 0–18. But if your child falls under the average range, reach out to their pediatrician. It could be from malnutrition, but it could also be from other causes and underlying conditions.


If a child isn’t growing as expected, it might be from undereating. But delayed growth can also have other causes. Contact your child’s pediatrician for any concerns.

Not eating enough can negatively affect your skin. In some cases, it can cause the skin to thin, wrinkle, and even peel or tear.

The skin can also develop lesions, bruising, broken blood vessels under the skin, and even more significant bleeding under the skin called purpura.

A 2018 study found an association between malnutrition and skin tears regardless of age or BMI.

Malnutrition is when your body is not getting all the nutrients it needs. This can be caused by not eating enough, but there can be other causes, such as underlying medical conditions.

There’s also some conflicting evidence that calorie restriction may be beneficial for the skin.


Not eating enough may negatively affect the skin, but more research is needed to understand the relationship between calorie reduction and how it affects the skin.

The bottom line

Although overeating increases the risk of developing health problems, undereating can also affect your health. This is especially true with severe or long-term calorie restriction.

If you notice any of the signs above, consider if you’re eating enough and then contact a healthcare professional for advice.

To make sure you’re getting enough to eat, the Dietary Guidelines for Americans suggest females get at least 1,600 calories a day and males at least 2,200 calories. These are the minimum values for weight maintenance.

Still, everyone’s body is different. You can always reach out to a doctor or dietitian for advice on what will work best for you.

If you believe you aren’t eating enough and need extra support, you may want to reach out to a healthcare professional or organization like the National Alliance for Eating Disorders.