Can You Undereat And Not Lose Weight? (Yes, Here’s Why)

When you’re trying to lose weight, a common approach to doing this is by significantly decreasing the number of calories that you are consuming daily.  

But, can you undereat and still gain weight? 

Yes, you can undereat and still gain weight. The primary reason is due to being in a drastic caloric deficit for too long, which causes your body’s hormonal profile to change, making it harder to lose weight, and likely causing your metabolism to slow down greater than when you first started dieting.

As a nutrition coach, this is one of the most common frustrations clients have before working together.  They’ve substantially cut calories but don’t understand why they are continuing to gain weight. Just like overeating, undereating can harm your body’s health.

In this article you’ll walk away learning:

  • What is considered undereating?
  • What are symptoms of what undereating may feel like?
  • Why might you be gaining weight while undereating?
  • What do you do if you are undereating?

What Is Considered Undereating?

What is considered undereating?

The term undereating is quite subjective.  The act of undereating will vary from person to person as each individual has different requirements for nutrition and caloric intake.  

Put simply, undereating is consuming less food than what the body demands to maintain its current weight.  This can be done purposely by following a reduced-calorie diet or unknowingly by increasing exercising and not refueling adequately afterward. 

If you are trying to lose weight, your caloric intake (the number of calories that you are consuming) will be less than your calorie expenditure (the number of calories that your body is burning throughout the day).  

At this point, you are considered to be “undereating” based on the calories in versus calories out balance equation.  

But what is important to understand is that due to the subjective nature of this term, undereating is not considered to be the same as extreme calorie deficits, eating disorders, or illness.  

You can 100% decrease your caloric intake in a healthy, calculated way that still allows your body processes to function as needed while reaching your weight loss goals.

Undereating becomes a problem, and can affect your weight loss goals, when you start to experience certain symptoms related to malnourishment.  

What Are Symptoms Of Undereating?

What are symptoms of undereating?

Here are some of the most common symptoms of when undereating becomes unhealthy:

  • Constant feeling of hunger
  • Poor concentration and focus
  • Low energy levels & fatigue
  • Hair loss
  • Sleep issues
  • Feeling irritable
  • Constipation

If you’re experiencing any of these things, you might be underrating in an unhealthy way, which leads us to some of the reasons why you might not be losing weight despite your caloric deficit.  

3 Reasons You May Be Gaining Weight While Undereating

3 reasons you may be gaining weight while undereating

The three reasons you may not be losing weight while undereating are: 

  • You Have Hormonal Imbalances
  • You Have A Slower Metabolism
  • You’re Not Tracking Calories Accurately

The first two reasons (hormonal imbalances and slower metabolism) will happen if you’re experiencing any of the symptoms of undereating that I mentioned above.  

The third reason (not tracking calories accurately) has more to do with thinking you’re undereating, when in reality, you’re actually eating in a caloric surplus. 

1. You Have Hormonal Imbalances

If you have been dieting (a reduced calorie intake) for an extended amount of time (months or years even), hormonal changes are going to take place in your body.  

One of the key hormones this will affect is cortisol.  Cortisol is a stress hormone that will help to regulate our body when we are in a state of stress.  This includes over-exercising, a stressful day at work, losing a loved one, being stuck in traffic, you being late for an appointment, etc.  

One of the important roles of cortisol is to curb non-essential functions in the body during a flight-or-fight response (i.e. when you’re experiencing stress).  If your cortisol levels are in a state of constant heightened activation, this could lead to you not losing weight due to an imbalance of many other hormones in your body. 

Even though you are working out and feeling like you are doing all of the things right, you may be hindering your progress unintentionally.

2. You Have A Slower Metabolism

If you have ever decreased calories, you may have noticed that initially, your body reacts favorably and you lose weight.  If you are someone who has struggled with chronic dieting, this is something that becomes more challenging every time you drop calories. 

If you do not feed your body with enough calories, over time your metabolism will slow down as it doesn’t need to digest and use as much energy.  

So what does this mean for you? It means that you won’t be burning as many calories or as much body fat when you are working out.  Even if you spend time exercising every day, you will notice a very slow or unresponsive reaction to weight loss.  

Again, if you’re experiencing any of the signs of undereating, then you may also be experiencing a slower metabolism.  

If this happens, you may want to consider implementing a refeed day, which is a temporary increase in calories for 1-2 days in order to boost your metabolism during a dieting phase.  

You can learn more in my article 7 Signs You Need A Refeed Day

If you want to increase your metabolism, it’s important to provide your body with enough energy for it to know that it has enough energy coming in.  

Related Articles:

3. You’re Not Tracking Calories Accurately

Are you tracking your calories or macros intake?  If so, accuracy is one of the key components to success.  When tracking calories, it is important to not only accurately track portions but to include all ingredients.  

Some of the most common errors made while tracking is:

  • Not including every bite, lick, and taste.  These can add up quickly to hundreds of calories in a day.
  • Not including cooking oils.  Each tablespoon of Olive Oil has 14g of fat or 126 calories.  If you are not counting your cooking oil and using 2-3 tablespoons to saute your vegetables, that’s up to an additional 378 calories you are consuming that are unaccounted for.
  • Guesstimating your portion sizes instead of weighing your food.  This can significantly affect the amount of food that you are consuming.
  • Not tracking condiments or sauces.  These count too and typically include a higher amount of carbohydrates and fats.  

If tracking, I highly suggest taking 30 days to focus on accuracy and consistency to truly ensure that you are consuming enough calories and not overconsuming.  

What Can You Do If You Are Undereating & Want To Lose Weight?

What can you do if you are undereating and want to lose weight?

If you are undereating and gaining weight (or not losing weight), here’s what you can do next:

  • Focus on sleep quality
  • Include stress management in your daily routine
  • Eat protein at each meal
  • Make sure you have a balanced plate
  • Eat until satisfied
  • Determine resting metabolic rate
  • Consult a nutrition coach for assistance

1. Focus on Sleep Quality

Prioritizing sleep and wind down routine can help to ensure that you are getting enough quality sleep each night.  

This is important to help lower cortisol levels and allow your body to get the rest it needs.

2. Include Stress Management in Your Daily Routine

Eliminating stress entirely is not realistic but including ways to manage the stress you are dealing with will help to lower cortisol levels.  

In addition, it will give you a chance to rest and give yourself time to find different ways to manage the stress that do not necessarily add to your already existing stresses.  

An example is to find alternate ways to manage stress aside from exercise.  

Although this is important for our mental health and overall wellness, it is still a stress on the body.  Instead, taking 20 minutes to do a passive activity (read, meditate, draw, etc) can be helpful to manage stress and not add to current stress levels and cortisol levels.  

3. Prioritize Protein

Including protein at each meal will not only help to maintain lean muscle mass during a period of dieting, but also help you to feel satiated between meals too.  

Your body requires protein for many different reasons including hormone regulation and enzyme production.  

Therefore, if you’re eating a low protein diet AND eating in a caloric deficit, your natural hormone production may be negatively impacted. 

4. Balanced Plate

At each meal, try to focus on a balanced plate including protein, complex carbs, 1-2 servings of vegetables, and healthy fats.  

This will help to ensure that you are not only eating enough but that you are getting enough micronutrients (vitamins and minerals), as well as macronutrients (protein, carb, and fat).

5. Eat Until You’re Satisfied

If you are undereating with the goal to lose weight, instead of excessively cutting calories try to instead eat until you’re satisfied and not stuffed.  

This will help to ensure that you are feeling satisfied with the balanced plate you are eating but not overconsuming either.  

6. Determine Resting Metabolic Rate

Resting Metabolic Rate (RMR) is the number of calories that your body requires to exist without taking into consideration your activity levels throughout the day (exercise and non-exercise activity).  

By determining this number, you are able to ensure that if you are reducing calories, you are not going below this number.

This will help to ensure that your body is receiving enough calories in order for it to function adequately (pump blood through your body, hormone production, and secretion, proper digestion, etc.).

Check out this RMR Calculator.

7. Consult A Nutrition Coach

If you are struggling to determine if you are undereating or how to start increasing foods, try consulting a nutrition coach that aligns with your values.  

There is nothing wrong with asking for help from someone who is educated and experienced with safe weight loss approaches and nutrition habits.  

Connect with us at FeastGood and we can discuss setting up a personalized nutrition plan that doesn’t involve drastically undereating in order to lose weight. 

Final Thoughts

Consuming fewer calories than your body requires can be a safe way to lose weight.  However, it is important to ensure that you are not consuming too few calories for your body to function adequately.  If you do, there is a chance you may experience weight gain instead of loss.  

What To Read Next

I mentioned that it’s important to increase your protein intake.  However, sometimes it’s hard to do that while not also increasing your fat intake. 

If you’re exercising really hard and not losing weight, then check out my article I Burned More Calories Than I Ate And Still Gained Weight to learn why this might happen. 

If you need a solution to track your calories and macros, check out my review of the MacroFactor App and why I think it’s way better than MyFitnessPal. 

Finally, learn more about weight loss in this article Do Macros Matter for Weight Loss? (Yes, Here’s Why).

Other Weight Loss Articles


Hirotsu, C., Tufik, S., & Andersen, M. L. (2015). Interactions between sleep, stress, and metabolism: From physiological to pathological conditions. Sleep science (Sao Paulo, Brazil), 8(3), 143–152.

Derma, F. and Zaborowska, Ł. “RMR Calculator – Resting Metabolic Rate”. Available at: Accessed: 13 August 2023.

About The Author

Caryn Watt

Caryn Watt is a certified personal trainer & nutrition coach. Working primarily with women all over the world, she focuses her time on helping clients learn more about nutrition and the importance of improving their relationship with food through tracking macros, movement, and mindfulness.

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