Why Can’t I Gain Weight No Matter What I Do?

QUESTION: I want to build muscle and gain weight, but I’m having trouble. I’ve always been naturally skinny. I’m the typical “hardgainer” with an “ectomorph” body type that has hardly any muscle mass.

I’ve been working out and eating a ton of food every day to change that, but it’s not working. Why does it seem like I can’t gain weight no matter what I do?

ANSWER: This is a question I hear all the time from both men and women.

They tell me the same story about how they’ve been really skinny their entire life, how they eat tons and tons of food, with tons and tons of calories, and they’re using an effective weight training workout, and on and on and on.

But yet, despite doing all of this, they’re still not gaining any weight.


Well, as someone who has the same naturally skinny, hardgainer/ectomorph story (I started at 5’11” around 120lbs), this is a problem I have plenty of personal experience with, and I know exactly how to solve it.

Here’s What You Think The Problem Is

Most people who can’t gain weight despite working out and eating a ton will assume the problem has to be one or more of the following:

  • They’re not using the right workout routine.
  • They’re not doing the right exercises.
  • They’re not using the right advanced training methods.
  • They’re not taking the right supplements.

But I can promise you, it’s none of these things.

The Real Reason Why You Can’t Gain Weight

There is only one reason – I repeat… ONE REASON – for why you’re not gaining weight.

It has nothing to do with your workout. Or exercises. Or training methods. And it sure as hell has nothing to do with supplements.

However, it has everything to do with your diet.

Specifically, your calorie intake.

More specifically? You’re not eating enough calories.

That’s literally all there is to it. Let me explain…

How To Gain Weight: The One Requirement

While there is a lot involved in the muscle building process, and a lot involved in making sure the weight you gain is muscle rather than body fat (a topic I wrote a book about: Superior Muscle Growth), there is only one factor involved in gaining weight.

Or, I should say, there is only one requirement that needs to be met.

And that is, you must be in a consistent caloric surplus.

If you are, you’re going to gain weight. If you’re not, you won’t.

Simple as that.

Now just what is a caloric surplus, you ask? Here are the basics…

Calories In vs Calories Out

  • Calories In
    Everything you eat and drink contains calories. With the exception of obvious stuff like water, all foods and drinks contain some amount of calories, which of course go on to make up your calorie intake. Since these are the calories being consumed and therefore taken in by your body, they are commonly referred to as your “calories in.”
  • Calories Out
    Everything you do burns calories. From intense exercise like weight training and cardio, to basic daily tasks like standing, talking and brushing your teeth. In addition, your body actually burns a very significant number of calories each day on its own just keeping you alive and functioning properly (breathing, pumping blood, digesting food, etc.). Since these are the calories that you are using and burning, they are commonly referred to as your “calories out.”

Now, when you consume the same number of calories that you burn (calories in = calories out), you will maintain your current weight. This is known as your maintenance level.

Maintenance: This person will maintain weight.
This is “maintenance.”

However, if you consume fewer calories than you burn (calories in < calories out), your body will burn some form of stored energy (body fat, muscle or both) for fuel instead. This is a state known as a caloric deficit, and it is a requirement for losing weight.

Caloric Deficit: This person will lose weight.
This is a “caloric deficit.”

On the other hand, if you consume more calories than you burn (calories in > calories out), the leftover calories that didn’t get burned will be stored on your body for later use (as muscle, fat or both). This is a state known as a caloric surplus, and it is a requirement for gaining weight.

Caloric Surplus: This person will gain weight.
This is a “caloric surplus.”
Which means, if your goal is to gain weight, you must be in a consistent caloric surplus.

And as long as you’re doing everything else correctly while in that surplus, much of the weight you gain will be muscle rather than body fat. If you’re not, the opposite will happen.

But regardless of everything else, a caloric surplus is the sole requirement here.

So if that is indeed your goal, but it’s just not happening… THIS IS ALWAYS YOUR PROBLEM. You’re simply not eating enough and your required surplus doesn’t exist.

But wait… hold on.

What’s that you’re saying?

Ohh, I know exactly what you’re saying now.

“But I’m Eating A Ton Of Calories, I Swear!!!”

Yup, there it is.

This is the line I hear from everyone.

And it’s the exact same line I used to say back in the day when it seemed like I couldn’t gain weight no matter what I did.

People who were more knowledgeable and experienced than I was at the time would then tell me I wasn’t eating enough, and I would swear up and down that “I’M EATING A TON!!”

Since then, I’ve spent the last 15 years having this very same conversation from the opposite perspective.

Now people complain to me about how they can’t gain weight… at which point I tell them they’re simply not eating enough… at which point they tell me that they are “EATING A TON!!!” and there is “no possible way they aren’t eating enough.”

Ah yes… it really has come full circle.

But Here’s The Thing

You’re still not eating enough.

No matter how much you think you’re eating, how much you claim to be eating, or how much you may even legitimately be eating… if you’re not gaining weight, you’re still not eating enough.

That’s all there is to it.

That is the problem – and eating more calories is the solution – 100% of the time.

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Why Does It Seem Like You “Eat A Ton” But Can’t Gain Weight?

At this point, you may be wondering why this scenario happens.

Why do people like you and me feel like we have to eat WAY more calories than everyone else in order to gain weight? Why does it feel like we’re “eating a ton” but yet it’s still not enough?

Well, the quick and easy answer is that some people are more resistant to weight gain than others. Meaning, it is harder for some people to get into a caloric surplus.

And if you’re reading this article, chances are you’re one of those people.

Us naturally skinny, ectomorph/hardgainer types just happen to have a few factors working against us in this regard.

What factors, you ask? These are the main ones…

  1. Hormones
    In some cases, hormonal factors (e.g. thyroid, leptin, ghrelin) can be affecting your metabolic rate or hunger levels.
  2. Digestion
    Sometimes, it’s a digestive issue. Because if you’re not properly digesting some/many of the foods you eat, then you’re not properly absorbing the calories/nutrients they contain. Me personally? I have issues with diary, oats and wheat.
  3. Hunger/Appetite
    In many cases, people who claim to be “eating a ton” aren’t actually eating a ton at all. Those of us with “skinny genetics” tend to be picky eaters (I certainly was/still am) who don’t always have the largest appetites in the world (I certainly didn’t, but this has improved significantly over the years). This at least partially ties in with the hormonal factors mentioned before – specifically with leptin and ghrelin – as they are the hunger regulating hormones. But regardless of the cause, you’d be surprised at how many times someone who claimed to be “eating tons and tons of calories” finally started tracking their diet and discovered they weren’t eating nearly as much as they thought they were.
  4. Activity Level/Lifestyle
    It’s always funny when someone asks me why they can’t gain weight, and they go on to explain that they weight train 5 days a week, do an hour of cardio after every workout, do HIIT 3 times a week, play sports like soccer or basketball a few times a week, are currently training for a marathon, and do a little MMA training on the side. “Why can’t I gain weight???” Um, because you’re burning a shitload of calories, and that’s making it significantly harder for you to eat enough to end up in a surplus. The solution? Cut back on activity, or eat even more to compensate. Those are the only options. Details here: Does Cardio Kill Muscle Gains?
  5. NEAT
    And finally, the most significant factor of all. NEAT (non-exercise activity thermogenesis) represents all of the calories your body burns during all forms of movement besides exercise. This includes normal daily activity like brushing your teeth, walking around a store and doing whatever you happen to do for a living (working at a desk vs being on your feet doing some kind of physical job can make a HUGE difference in calories burned), as well as subconscious/spontaneous movement you aren’t even aware of (like fidgeting, adjusting posture, etc.).


    And the interesting thing about NEAT is that, for most people, it increases in response to eating more (all part of your body’s desire to maintain homeostasis). Meaning, when you eat more calories in an attempt to gain weight, you will automatically (and unintentionally) start moving/burning more… thus unknowingly wiping out some part of the surplus you’re attempting to create. Even more interesting? The degree that this occurs can vary by hundreds or even thousands of calories from one person to the next (source). It’s likely the biggest reason why some of us have to eat WAY more than others.

So yeah, it may not be your imagination. One or more of these factors may very well be making it harder for you to gain weight.

Of course… none of this changes the fact that the solution remains the same: you need to eat more calories.

How many exactly? Let’s figure it out.

How Many Calories Should You Eat A Day?

Well, let’s answer this question from two different perspectives…

1. To Gain Muscle (Not Fat)

For most of the people reading this, the goal is going to be gaining weight in the form of muscle mass rather than body fat.

To do this, the average man should aim to gain about 2lbs per month (about 0.5lb per week), and the average woman should aim to gain about 1lb per month (about 0.25lb per week).

This tends to be a good starting point for finding the best balance between maximizing muscle gains and minimizing fat gains.

The only question is, how many calories do you need to eat a day to be in the surplus that makes this happen? Here’s what I recommend…

  1. Multiply your current weight (in pounds) by 14-16, and then start eating an amount of calories within this range each day.
    For example, a 150lb person would do 150 x 14 and 150 x 16 and get a range of 2100 – 2400 calories. Those who are female or less active both in terms of their job/overall lifestyle and how much exercise they do should usually stick more toward the lower half of their estimate. Those who are male or more active should usually stick more toward the upper half of their estimate. If you’re unsure, just pick a number somewhere in the middle.
  2. Weigh yourself every day and take the average at the end of the week.
    Always do it first thing in the morning before eating/drinking (but after peeing), and try to wear the same amount of clothing (ideally none) each time. Additional details here: When Is The Best Time To Weigh Yourself
  3. Pay attention to the weekly averages for the next 2-4 weeks.
    Ignore the meaningless daily weight fluctuations you might see, and instead only pay attention to what your average weekly weight is doing over a span of 2-4 weeks.
  4. Ask yourself this question: am I gaining weight at the recommended rate?
    If the answer is yes, you’re all good. Keep eating this amount of calories and continue monitoring progress this same way. If the answer is no, then adjust your calorie intake up or down in small increments (e.g. 100-300 calories at a time), wait another 2-4 weeks, and see what happens then. Are you gaining weight at the recommended rate now? If so, you’re good. If not, adjust again and repeat this process until you are.

And just in case it isn’t obvious enough, you’re going to want to combine this ideal calorie intake with an ideal overall muscle building diet AND muscle building workout routine.

I cover most of this stuff in my 15-step guide on How To Build Muscle, but if you’re looking for a program that puts everything together for the specific purpose of building muscle without gaining excess body fat, Superior Muscle Growth is as perfect as it gets.

2. To Just Gain Weight, Period

On the other hand, some people may just want to gain weight, and they don’t really care if it ends up being muscle, fat or a combination of both.

This obviously isn’t a goal I’d recommend to the vast majority of people (especially those in scenario #1), but it’s worth noting that there are indeed certain situations when this type of “just gain anything” goal may be warranted (i.e. when someone is underweight to an unhealthy degree).

So, how would you determine how many many calories to eat per day in these kinds of cases?

Simple. You’d repeat the exact 4-step process from scenario #1, only A) you can eliminate the other muscle building guidelines/requirements, and B) you can aim for a slightly faster rate of weight gain (e.g. 1-2lbs per week).

The End

And there you have it. The one huge, surprising, overlooked reason for why it seems like you can’t gain weight no matter what you do.

You’re just not eating enough.

That’s literally it.

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About Jay
Jay is the science-based writer and researcher behind everything you've seen here. He has 15+ years of experience helping thousands of men and women lose fat, gain muscle, and build their "goal body." His work has been featured by the likes of Time, The Huffington Post, CNET, Business Week and more, referenced in studies, used in textbooks, quoted in publications, and adapted by coaches, trainers, and diet professionals at every level.