How to Stop Undereating and Properly Fuel Your Body

In our culture, there’s an underlying fear of eating “too much.” This fear has led to the normalization of disordered behaviors that are supposed to prevent that from happening, like fretting over portion sizes and fixating on nutrition labels. This type of restrictive eating is often praised. But in reality, undereating is a major issue that carries life-altering and sometimes life-threatening side effects.

Undereating is a symptom of most eating disorders, but it can also show up in those without an official eating disorder diagnosis. It can stem from a wide variety of causes and triggers, including maladaptive coping mechanisms, feelings of shame and guilt, or simply life circumstances.

Research in Nutrients shows that undereating is especially prevalent in certain groups, such as athletes experiencing low energy availability (when energy intake does not meet the demands of energy expenditure). Some people may also unintentionally fall into chronic energy deficits because of hectic schedules, high levels of physical activity, or naturally low appetites. For others, undereating may be driven by deeper issues, like body image concerns, external pressure from family or coaches to maintain a low weight, or strict internal beliefs about food.

Unfortunately, undereating—and even setting goals to eat less—is often normalized and praised, with little recognition of its negative consequences. Below, we’ll define undereating, identify its health risks, and explore strategies to help you or a loved one stop.

Undereating: What it means (and how to fix it)

Undereating means not getting enough calories or essential nutrients (or both) to meet your body’s needs. It can happen intentionally or unintentionally, and you may not always feel hungry when your body needs more fuel. Addressing undereating generally involves eating enough and consistently, rebuilding awareness of your body’s cues, and getting individualized support when needed.

“It's essentially a state where your body isn't receiving enough energy and nourishment to support its basic metabolic processes, physical activity, and overall mental and physical health,” explains dietitian Crystal Fox, MS, RDN.

Your body needs a significant amount of energy just to stay alive and function. Your basal metabolic rate covers the energy needed for basic functions like breathing and cell repair, while extra energy supports physical activity, digestion, and other everyday demands.

Exactly how much energy and nutrition someone needs varies widely. Energy and nutrient needs depend on factors like age, activity level, genetics, body composition, and health status. Someone recovering from an eating disorder, for example, may need additional energy to support recovery and weight restoration, on top of the energy needed for everyday functioning and activity.

That’s also why online calorie calculators aren’t a reliable way to determine whether you’re eating enough. They use generalized formulas for energy needs that are highly individual and can change depending on your circumstances.

That said, undereating also isn’t always intentional or obvious. Dietitian Erin Kuta, MPH, RD explains that it can “involve both intentional restriction and unintentional patterns, often influenced by the brain-gut connection.”

“For example, stress, overwhelm, and living in survival mode can suppress appetite and blunt hunger cues, making it hard to rely on stomach hunger alone,” Kuta says. That’s why she also looks for other signs—like low energy, brain fog, headaches, mood changes, and digestive issues—that may suggest someone isn’t getting enough nourishment even if they don’t feel hungry.

If you’re unsure whether you’re undereating, a registered dietitian can help assess your energy and nutrient needs and develop a plan to meet them consistently.

The health risks of undereating

Whether or not someone has an eating disorder, consistently not eating enough can affect nearly every system in the body. Over time, inadequate energy and nutrient intake can impact your brain, mood, digestion, hormones, muscles, heart, and immune system.

Mood and personality changes

Undereating can make it harder to regulate your emotions and may contribute to irritability, anxiety, depression, low energy, social withdrawal, and mental rigidity.

Nutrient deficiencies can also affect brain and nervous system function. In fact, a 2023 review in Nutrients linked low levels of nutrients including B vitamins, vitamin D, magnesium, zinc, selenium, iron, calcium, and omega-3 fatty acids with depressive symptoms.

Food obsession and cognitive issues

When your body isn’t getting enough energy, thoughts about food can become increasingly difficult to ignore. For instance, in the landmark Minnesota Starvation Experiment, men who were intentionally underfed developed a food obsession and experienced problems with concentration, learning, and judgment.

Additionally, a 2021 meta-analysis on anorexia published in Neuroscience & Biobehavioral Reviews shows that undereating can also make daily tasks harder, contribute to brain fog, and is linked to memory issues.

Decreased metabolism

Undereating can lower your basal metabolic rate (or the energy your body needs for basic functions). When fuel is low, the body slows down to conserve energy, prioritizing survival over efficiency.

Reproductive issues

Losing your period for more than three months—known as amenorrhea—is a common sign of undereating and can lead to serious issues like infertility and osteoporosis.

One 2022 review in Reproductive Medicine & Biology concluded that low energy availability from undereating can suppress all reproductive hormones. This is because the body conserves calories by prioritizing essential functions and shutting down other processes like reproduction.

Nutrient deficiencies and muscle loss

Not getting enough food can lead to nutrient deficiencies associated with problems such as anemia, hair loss, bone loss, cold intolerance, fatigue, dizziness, and weakened immunity.

When the body doesn’t have enough energy available, it may also break down muscle tissue for fuel. In severe cases, prolonged undereating can affect the heart, potentially lowering heart rate and blood pressure or contributing to dangerous heart rhythm changes.

Digestive problems

Undereating can also disrupt digestion. Research in the Cleveland Clinic Journal of Medicine suggests that malnutrition and weight loss can slow movement through the digestive tract, contributing to symptoms such as constipation, reflux, bloating, and gastroparesis (delayed stomach emptying).

Feeling out of control around food

Restriction can also disrupt hunger and fullness cues. When you’re underfed, your body may respond with intense hunger, binge eating, or a sense of being out of control around food. This can contribute to a cycle of restriction followed by overeating, guilt, and further restriction.

Weakened immune function

Chronic undereating can make it harder for the immune system to function properly, potentially increasing susceptibility to illness and slowing recovery and wound healing. Inadequate intake can also lead to deficiencies in nutrients that support immune function, including protein, essential fats, vitamins A, C, and D, zinc, and selenium.

Free eating disorder screenerWorried you or a loved one aren’t eating enough? Taking a free screener is a great next step.

Take the screener

How to stop undereating

Starting to eat enough food after a period of undereating can be challenging—especially if you have an eating disorder—because there are often several factors at play.

However, eating enough food is a necessary and foundational step towards restoring your health and well-being, and with the right tools and support, it’s completely possible. Here are ten expert-backed ways to stop undereating:

Identify the underlying issue

“It’s important to identify the root cause of the undereating and address it accordingly,” Fox says.

If you have an eating disorder, undereating likely serves an emotional purpose, such as numbing or indirectly expressing difficult feelings, and is probably driven by intense eating disorder thoughts.

If this is the case, it’s best to work with a therapist and dietitian to help you understand what’s driving your food behaviors. Sometimes, it’s not until after you’ve started eating enough food that you can fully understand why you weren’t eating enough.

If you don’t have an eating disorder, perhaps undereating is caused by external factors like an overpacked schedule, appetite-suppressing medication, a condition like attention deficit hyperactivity disorder (ADHD), or a combination of issues.

Is it an eating disorder?Our free, 5-minute screener can help you determine if you should be worried.

Take the screener

Understand that everyone has different needs

As I explained above, energy needs vary from person to person and depend on several factors.

“To better fuel your body, you really need to stop listening to all the noise out there of ‘only needing X amount of calories,’ because bodies are individual and each requires different levels of fueling to feel their best,” explains Equip Lead Dietitian Stephanie Kile, MS, RDN.

Comparing what’s on your plate to your friend, mother, or sibling may be tempting, but it isn’t helpful for meeting your unique energy and nutrient needs.

Eat consistently throughout the day

“Stick to the idea of getting in three full meals and two snacks a day, aiming to have something to eat every three to four hours during waking hours,” Kile suggests (some people may need fewer or more snacks).

If you’re not able to get in all meals and snacks yet, start by eating at least something every few hours and work your way towards enough.

For example, if you’re not eating breakfast regularly, start with a snack that includes carbohydrates, protein, and fat (like a banana with peanut butter) and then work towards eating a complete breakfast (like having bread and a latte or yogurt with the banana and peanut butter).

“Consistency matters more than perfection,” Kuta adds.

Shoot for a relatively balanced plate

First, identify the meal’s carbohydrates, since “most of your intake should be from grain-based carbohydrates, like bread, pasta, and rice, which are the top fuel source your body needs to function optimally,” Kile explains.

Then, include a protein source, like meat, beans, or fish.

Next, make sure there’s some fat. “This can be in the sauce or dips you add to a meal, butter on bread, the oil you cook with, avocado, nuts, cheese, and so on,” Kile shares.

Finally, include some fruits or veggies that you enjoy.

“Making sure to get all of these aspects in your meals and snacks will help to make sure you’re not undereating during the day,” Kile says. “If you’re skipping one of these nutrients, that would most likely cause you to undereat.”

Keep in mind that not every meal needs to be perfectly balanced, and that aiming for relative balance is just fine.

Lean on meal plans or mechanical eating when necessary

After periods of undereating, hunger and fullness cues are often absent or unreliable at first. And if you have an eating disorder, chances are high that your eating disorder thoughts get louder as you start to eat more.

If this is the case for you, a meal plan or mechanical eating (or both) could be the best route for now.

“Prescriptive meal plans can be a tool to help one begin to learn their needs when they are unable to regulate it naturally,” Fox explains. Mechanical eating, or eating by the clock, is a helpful and often temporary tool to get your body out of an energy deficit and into a regular eating rhythm.

Have back-up meals and snacks

“Keep go-to meals and snacks on hand that feel doable when energy and appetite are low,” Kuta suggests.

In my practice, my clients find it helpful to create a list of such meals and snacks, and then make sure they have those items or ingredients stocked in their kitchen (or stashed in a purse or bag when on the go).

Some examples of simple back-up meals include peanut butter and jelly sandwiches with a side like chips and salsa or veggies and hummus, or a snack plate of cheese and crackers, grapes, cashews, and turkey or ham slices. Some snack ideas are yogurt with granola or trail mix with peanuts, chocolate, and dried cranberries.

Consider logging your food

Sometimes, keeping track of what you eat can be helpful for identifying physical, emotional, or mental barriers to getting your needs met. Many of my clients like to use apps like Recovery Record or Nourishly, while others like to simply jot down their intake and insights in a journal (avoid weight-loss- and calorie-focused tracking apps, like MyFitnessPal).

However, be mindful about this strategy and pay attention to how it makes you feel—for some people with eating disorders, logging food can cause anxiety and distress.

Check in with yourself

Take a couple of minutes throughout the day to take some inventory of your body and mind.

“Check in with your body for signs you might need food, like fatigue, foggy thinking, or irritability, even if traditional hunger isn’t present,” Kuta recommends.

Perhaps you are connected to your hunger cues, and you realize you’ve been ignoring them. It can also help to notice the thoughts and beliefs you have about meeting your energy needs, because societal or familial conditioning can contribute to undereating.

“Remember, your body needs nourishment even when you don’t feel hungry, productive, or ‘deserving,’” Kuta adds.

Use tools during and around mealtimes

Whether or not you have an eating disorder, using nervous system regulation tools can help you slow down and feel safe enough to eat enough.

“Consider pairing eating with nervous system grounding, like placing your feet firmly on the floor or taking a few slow, deep breaths to minimize overwhelm and support digestion,” Kuta says.

If there are mental and emotional barriers at play, bringing coping tools from therapy in and around mealtimes can be helpful. Some examples are self-compassion, challenging black-and-white thinking, and mindfulness.

Work with a registered dietitian

Working with a non-diet dietitian is the best way to understand your body’s nutrient and energy needs and remove barriers to eating enough food every day. A dietitian will guide you and support you through the process, taking into account the reasons why you undereat, medical and health status, and personal preferences.

If you have an eating disorder, it’s best to work with an eating disorder-trained dietitian as well as a therapist to help tackle emotional and mental challenges that often arise once you’re eating more food.

Eating enough food is an essential action to support your mental, emotional, and physical health and well-being, whether you’re in recovery from an eating disorder or not. Putting a stop to undereating and fully meeting your energy and nutrient needs is often nuanced and challenging, and usually requires professional guidance and support. When you’re ready, reach out to a non-diet dietitian or Equip to help you get there.

The bottom line

Stopping undereating can take time, especially when hunger cues are unreliable or eating more brings up difficult thoughts or emotions. Start by identifying what’s making it hard to eat enough, then focus on consistent meals and snacks, relatively balanced nutrition, and practical tools that make eating easier. A registered dietitian can help you determine your individual needs and build a plan for meeting them consistently.

FAQ

What is undereating?

Undereating means not getting enough calories, essential nutrients, or both to meet your body’s needs. It can be intentional, such as restricting food. It can also happen unintentionally due to factors like a busy schedule, low appetite, stress, certain medications, or other circumstances.

How do you stop undereating?

To stop undereating, start by identifying what’s making it difficult to eat enough. Eating meals and snacks consistently throughout the day, aiming for relative balance, keeping easy back-up foods available, and using a meal plan or mechanical eating when hunger cues are unreliable can all help. Professional support may also be important, especially if an eating disorder is involved.

Can a dietitian help with undereating?

Yes. A registered dietitian can help determine your individual energy and nutrient needs and identify barriers that may be keeping you from meeting them. If you have an eating disorder, consider working with an eating disorder-trained dietitian alongside a therapist who can address the emotional and mental challenges that may come with eating more.