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Why Can't I Gain Weight?

The Detailed Guide For How To Eat And Workout For Results

by: Zack Mathews NASM - CPT, CES, & PES, PN-L1

Have you ever looked in the mirror and said “why can’t I gain weight!?” 

You are working hard in the gym and eating everything in sight, but your body never changes. 

It sucks, I know!  I've been there right with you.

Why can't I gain weight transformation picture

You might be in the same boat as I was in the left picture.  Self conscious, envious of people in better shape, and frustrated that nothing is happening.

What thoughts come to mind about your current physique?

If there are negative thoughts floating around that brain of yours, it’s time for you to learn what you need to do to get on the right track and become the best version of yourself.

Why you can't gain weight will be a question of the past after you learn:

The #1 Reason Why You Aren't Gaining Weight

I wish there was a secret I had that you have never heard before.

Unfortunately there is not.

Whether you are trying to gain weight or lose weight, it always comes back to the principle of calories in versus calories out.

To answer your question of why can’t I gain weight, the reason is because you are not eating enough calories.

Let that sink in.

Maybe we need to say it louder for the people in the back.

The reason you aren’t gaining weight is because you are not consuming enough calories!!

Let’s break down how calories in versus calories out works.

why can't I gain weight explaining calorie maintenance

Here we have an example of what calorie maintenance would look like.  This man, let’s call him Freddie, any Queen fans around? 

Fred eats 2500 calories a day.  His body also burns 2500 calories a day, which come from exercise, walking, eating, digesting food, normal everyday functions, etc.

Since his calories consumed equals the amount of calories burned, there is a net calorie difference of zero.  No calories are being stored or burned.  Fred’s weight will stay the exact same.

why can't I gain weight calorie surplus infographic

Now let's change one thing. 

Instead of Freddie consuming 2500 calories, he now eats 2800 calories.  Since his body only needs 2500 calories to perform all its daily functions, the extra 300 calories will become stored energy.

That stored energy will either become fat or muscle, thus making the scale go up. 

Fred is in a calorie surplus, and this is where you want to be.  You will always gain weight if you are in a calorie surplus.

As for whether those excess calories will be stored as fat or muscle, we will get into that later!

calorie deficit inforgraph

To round out this discussion, let’s say Fred actually only consumes 2200 calories instead of 2800. 

Remembering that since he burns 2500 calories everyday, he is now missing out on 300 calories that his body needs.

To make up the difference, his body will take from his extra fat or muscle storage units to get that 300.

This is what makes a calorie deficit, and this is what makes your weight go down.

Where are you currently at with your calorie consumption?  Has your weight been stalled for a long time?   Well, then you are at maintenance.  If it’s been slowly going down, uh oh, it’s time to get out of that calorie deficit.

Always remember, if you think to yourself, “why can’t I gain weight?”, it’s because you are not in a calorie surplus. 


Daily Activities That Are Causing Your Lack Of Weight Gain

Now that we know that you need to be in a calorie surplus to gain weight, let’s take a look at some other factors that preventing you from gaining weight.


Think about your daily life and what you like to do.  If you have a job that requires lots of moving and working with your body, you are going to be burning more calories throughout the day.   

What do your weekends look like?  

If you are out and about, going hiking, or playing basketball with your friends, your calories burned is going to be higher than the person who sits and watches Netflix all weekend.

I am not telling you to sit at home all weekend doing nothing, but you need to take into account your current lifestyle when figuring out how many calories you need to eat.



The type of exercise you like to do could be a clue to your question of to "why can't I gain weight?"

Cardio based workouts, although they are great for your heart health, can be going against what you are looking for with your physique.

Running on the treadmill, doing a crazy HIIT workout for 60 minutes, or doing long bike rides are all forms of exercise that are making it harder for you to gain weight.

You don’t have to give these things up if you love them, just focus on what you should be doing, and sprinkle these types of exercise in here and there.

I enjoy playing basketball.  It’s not the best form of exercise for gaining weight, but I enjoy it and want to do it.  I make up for it by eating extra calories the day that I play ball.  Do the same for the things you love doing.



Neat stands for Non Exercise Activity Thermogenesis.  What is basically means is the calories that you burn that are not coming from exercise.  Tasks like washing dishes, taking the trash out, tapping your foot like crazy because you can't sit still are all forms of NEAT.

This is where finding your proper calorie amount can be tough.  I’ll give you a rough idea of what you should be eating in a bit, but when it comes to NEAT, everyone’s calorie burn from NEAT is different!

Studies have shown that NEAT burn can be different by up to 2000 calories between people.  Although this is most likely from someone extremely sedentary vs active, it shows that it can vary from person to person.

Here's a great study about NEAT done in 2018.

Attention To Food Intake And Appetite

When it comes to gaining weight, ectomorphs are constantly not putting enough attention on their diet and appetite.

You are eating when you are hungry and stopping when you are full, which is great for most people.

But since you are needing to eat more calories, there has to be more attention on where you are at with your calories and how you are feeling.  You might need to start eating earlier in the day, have something extra at the end of each meal when you are already full, or add in another meal sometime in the day to get those extra calories.

Let’s get into ways that you can consume more calories.

7 Ways To Consume More Calories If You Can't Gain Weight

If you know you need to eat more calories but don’t feel like you can, this section will be for you.

Find something you can work on from this list, even if it’s just 1, to help you start eating more.

If you want to read about these more in depth, there is a whole article I wrote about ways to consume more calories.  Click the picture to read it.

Pick One Meal To Be The Big One

Go into your day knowing what meal is going to be the big one for the day.  Shoot for that meal to be close to 1000 calories. Knowing that one meal will take a big chuck of your calories will make the rest of the day seem more attainable.

  If you are a morning person, take it down at breakfast, if you like to eat later, do it at night.

Eat smaller, more frequent meals

If the above tip sounds like you’ll be walking around all day feeling lousy, opt for smaller, more frequent meals.

Instead of a 3 normal meals like most people have, go for 4 - 6 meals that have less calories.

If you need to eat 3000 calories, doing 6 meals at 500 calories is a lot easier than 3 big 1000 calorie dishes.

Drink A Homemade Mass Gainer

Mass gainer shakes are a great way to up your calories without having to worry about making a meal and taking the time to eat it.

I say homemade because the store bought mass gainers are full of garbage and will make you feel like garbage too.

Need a quick recipe?  Blend these ingredients together and you have a shake that is 945 calories with 67 grams of protein! Boooooom, easy  calories.


2 cups milk

1 1/2 scoops protein powder

4 tablespoons peanut butter

1 banana


Handful of spinach. Trust me, you won't taste it!

Liquid Calories

Playing off the last tip, just having more liquid calories, even if it’s not a big shake, will help greatly.

Milk is the way to go here.

Drink a cup full of milk AFTER 1 - 3 meals everyday. 

If you measure out 2 cups of whole milk, it’s close to 300 calories.  If you do that 3 times a day, that’s 900 calories with minimal effort.

Don't always eat clean

I made this mistake before.  Thinking I could eat 4000 calories of perfect food.  It’s hard to do, so if you can, props to you.

But don’t be afraid to add in some extra calories from foods you love.  That burger and fries you enjoy can be 1000+ calories of pure gains!

Stick to mainly healthy foods, and then add in the not so clean foods to help give you that added calorie boost.

Hardgainer Diet - Don't always eat clean. 80/20 rule

Eat Your Fats

This one is simple math.

1 gram of carbs or protein is 4 calories.  1 gram of fat is equal to 9 calories.  That’s more than double!

Consuming healthy fats will make a dent on your total calories when you need it without having to have a huge plate of something that might be hard to eat for you.

Load up on the nuts, peanut butters, avocados, and healthy oils for easy fat calories.

Have high calorie foods readily available

This is one of my go to’s.  I always try to have something in the fridge that I know I can grab if I need to load up on calories.

It’s usually pasta for me, but whatever you like, is high in calories, and is easy to warm up or cook is the way to go.

Pasta, bagels, cereals, oatmeals are all great choices.

Eating And Not Gaining Weight? Eat This Amount Of Calories & Protein

To get your body into a calorie surplus, there is an easy calculation to give you a great starting point.

Multiply your weight by 16 - 20 to get yourself a calorie surplus range if you're skinny and can't gain weight.

So if you are 150 pounds, a range of 2400 - 3000 calories would be where you would start.


Now, 600 calories is a wide range, so follow these tips to help you narrow it down.

    • Start on the lower range.  For this example, 2400 - 2600 would be ideal.
    • Follow these guidelines for 2 - 4 weeks to get a good picture of where your metabolism is currently at.  If you are not seeing changes on the scale, bump up to 2600 - 2800.
    • Be as accurate as you can with your tracking.

Why you should start on the lower end for your calories

In the example above, I recommended 2400 - 2600 calories instead of say, 2900 - 3000.  Wouldn't it make sense to start eating at the high end?

Not necessarily.  For this reason.


If you start your calories too high from the start, you are risking gaining excess fat.  The goal is to be in a slight surplus and pair it with a good workout program.  Therefore, your body will store those excess calories as muscle, instead of fat.


Another reason why starting lower on your calorie goal is so you have more room to grow. 

Imagine if you are able to build muscle at 2400 calories.  Once your body adjusts to that, you can go up to 2600, 2800, 3000 calories and see results. 

On the other hand, if you eat at 3000 calories form the start, your body will get used to that and you will have to keep pushing past that.

I don’t know about you, but eating in the 3500 - 4000 calorie range every day can get old fast.


What Are The Best Macros If I Can't Gain Weight?

When it comes to gaining weight, calories and protein are going to be the two most important things.

In terms of the other two macronutrient, carbs and fats, you can balance these anyway you prefer.

Protein is going to be the only macronutrient you are definitely going to want to track.

eating 4000 calories a day and can't gain weight macro guide

Protein Targets To Prioritize Muscle Building

Now that you know how to eat in a surplus, the next step will be making sure that you are eating enough protein.

Protein is the building block for weight gain muscle growth, and you need to be eating an adequate amount for your body to send the signal to build muscle from your workouts.

If you eat in a calorie surplus, but your protein is low, you are missing out on a lot of gains!

Studies show you can build muscle when you consume anywhere between 0.8 - 1.2 grams per pound of bodyweight. Read this study if you would like to learn more about protein levels.

Similar to calories, try and make yourself a range to hit to allow yourself flexibility.  A range of 10 - 20 grams of protein is perfect.  If you weigh 150 pounds, it between 130 - 150 grams per day.

If you want to build your bulking meal plan, check out this article.

The Best Bulking Diet Meal Plan For Skinny Guys

Why can't I gain weight high protein breakfast ideas

The Benefits Of Lifting Weights

We know you need to be in a calorie surplus to gain weight.

Additionally, we know you want to be consuming enough protein to build muscle.

How do you utilize that surplus and protein to build your body the right way?

You lift weights!

Lifting weights and following a muscle building program is the most beneficial thing a skinny person can do to change their physique and overcome not being able to gain weight.

I know you said you want to gain weight, but you really should be saying you want gain muscle.

That is what is going to give you the look you want, and make you way more confident than if you were to just put on fat from a calorie surplus.

What your workout program should include:

  • 2 - 5 hard workouts a week.
  • Workouts that will focus on your whole body or upper/lower splits.
  • Exercise selection should be a majority of big compound movements.  (Think of variations of the squat, deadlifts, bench press, etc).
  • Rep ranges anywhere between the 1-20 reps per set.  Most often you should stay in the 6-12 range, but occasionally have a movement push you toward the 1, or a high rep sequence pushing the higher limit.
  • Continually increasing weight, reps, or sets to send the signal for your body to build muscle.  This is called progressive overload and is the key to building muscle.
  • These are the main points when I design a Hardgainer Workout Program.
why can't I gain weight - use progressive overload

If your workouts focus on the above points, and your surplus and protein are on target, your body will start prioritizing the muscle building signal and start to add it onto your body.

If you need a workout program, check out the Ectomorph Body Type Weight Gain Guide.

The Low Hanging Fruit People Forget About When Trying To Gain Weight

I love talking about low hanging fruit.

Because I love to eat fruit? Yes, but that's not the reason.

These are the things you can do in your life to create a positive change with minimal effort.  Following a workout program 4 times a week and tracking every bite you eat is a challenge and will take a lot of work, but these two things can be easily followed with just a little effort and priority.

Get Good Sleep

You want to build muscle and change your physique. For your body to do that, your body needs down time to recover and grow.  What better place to do this than while you sleep!

It seems so simple, but it’s often overlooked.

We pound our bodies day in and day out, thinking this is what will get us results.  On the contrary, prioritizing sleep and being efficient during your time awake is the best thing that you can do for yourself.

Try and get 7 - 9 GOOD hours of sleep every night to optimize your muscle gain.


If you have trouble sleeping, here are a few tips to getting better sleep that may help you gain weight and muscle:

  • Eliminate blue light later in the evening to promote better sleep. Turn off your phone and tv earlier in the evening to promote more melatonin production.  A pair of blue blockers would be useful as well.
  • Keep your house dimly lit with lights or candles.  This will help your body send the signal that it’s time to settle down.
  • Keep your room cold.  Temperate for best sleep has been shown to be between 60-68 degrees.
  • Stop eating a couple hours before you go to bed to allow for your food to be digested.  This can be hard for ectomorphs when you are trying to add calories but do the best you can.
  • Be wary of stimulants later in the afternoon and evening.  Rethink that 5pm cup of coffee!

Manage Stress

When going along your weight gain journey, I want you to always be thinking about “what signal am I sending to my body?”

Your calorie surplus is sending the signal to store energy.  Your protein consumption and workouts are sending the signal to get stronger and build muscle.  Your 9 hours of sleep is sending the signal to your body to promote recovery.

All great things.

What about stress?

Some stress is good, but when your body becomes overly stressed, that stress will start taking priority and hormones will adjust to start fixing that. That means your muscle building hormones will take a back seat until your body feels you are a good place.

Managing your stress is one of your secret weapons to help you gain weight.  So find what works for you to help you destress and manage it better. Whether it’s going for a walk outdoors, listening to music, playing with your kids, find what is best for you and add it into your routine.

Frequently Asked Questions

I Eat 4000 Calories A Day. Why Am I Not Gaining Weight?


Very simply put, if you are eating 4000 calories and not gaining weight, one of two things is happenings.

#1 - You aren't actually eating 4000 calories.  Audit your diet and ensure that you are tracking all your food accurately.

#2 - This one is less likely but there is a chance that 4000 calories is your maintenance calories and you need to eat MORE calories to gain weight.

From my experience working with clients trying to gain weight, they usually are not tracking accurately.

Why Am I Not Gaining Weight In A Calorie Surplus?

Very simply put, if you are eating 4000 calories and not gaining weight, one of two things is happenings.

#1 - You aren't actually eating 4000 calories.  Audit your diet and ensure that you are tracking all your food accurately.

#2 - This one is less likely but there is a chance that 4000 calories is your maintenance calories and you need to eat MORE calories to gain weight.

From my experience working with clients trying to gain weight, they usually are not tracking accurately.

Why Can't I Gain Weight Female?

why cant i gain weight female

Whether you are a female or male, all the same rules of weight gain apply!  Eat in a calorie surplus to gain weight, eat enough protein to make sure you gain protein and not fat, and lift weights!

The only difference that I do with my weight gain females is tweak their workouts based on what body parts they want to target.

I've found most females like to work their legs, glutes, upper back, and arms so I will give them more of those exercises while men like chest, shoulders, and arms.

Let's Review Your Question Of Why Can't I Gain Weight And What We Learned

To sum up everything we discussed today and the main points for you remember, here are a few bullet points covering the article.

  • If you aren’t gaining weight, it’s because you are not in a calorie surplus.
  • A calorie surplus is when you bring in more energy, in the form of food, than the energy required by your body for its daily functions.  The left over calories will be stored for energy as fat or muscle.
  • Consider your everyday life activities to see if you are contributing to your weight gain journey or making it harder.
  • To consume more calories, follow this guide to see what will help you pack on the calories.
  • A good rule of thumb to get you in a calorie surplus is to multiply your weight by 16 - 20 to find a calorie range.
  • Keep protein high to help promote muscle growth. 0.8 - 1.0 grams per pound of bodyweight is a good range.
  • Follow a good weight lifting program that will help gain muscle and compliment your surplus and protein intake.  Follow this free 4 week plan.
  • Get good quality sleep.
  • Manage your stress.

There you have it!

I hope you find this article useful.  More importantly, I hope you leave this article knowing that you don’t have to keep asking yourself, “why can’t I gain weight?”, and you now know what you need to do to have the body of your dreams.

Happy gaining!

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