What Happens if You Lift Weights But Don’t Eat Enough Calories? (Solved!)

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Who else wants to know, “What Happens if You Lift Weights But Don’t Eat Enough Calories?”

This is a question I see time-and-time again, so it must be something that goes through many people’s minds.

If you’re not taking in enough calories, can you still build muscle?

Or is all that great training being completely ruined by your lack of calories?

Let’s find out.

What Happens if You Lift Weights But Don’t Eat Enough Calories?

If you lift weights but don’t eat enough calories you will eventually lose size and strength. How quickly this occurs will largely depend on your training experience and your current body composition. As an example, a gym beginner who is carrying a lot of body fat may still achieve size and strength gains while eating at a calorie deficit for 1-3 months. However, an intermediate lifter with lower body fat levels will see their size and strength decline much quicker.

The Impact of Training & Not Eating Enough

The Torso of a Muscular Main Eating Salad

To be honest, there really is no one-size-fits-all when it comes to training and under eating.

What I mean by this is that it will affect people differently depending on where they are in terms of their current training levels and body composition.

So, let’s assume that whoever you are that you regularly train the main compound lifts, i.e. squats, deadlifts, bench press, overhead press, bent-over rows, 4 times a week.

Plus, you also aim to progress in weight with each lift every week or couple of weeks.

In other words, you’re following a very basic training plan, but one that is proven to produce great results.

Here’s how not eating enough calories would affect you based on your training experience.


So, I would typically class someone still in their first 6-12 months of training as a beginner.

Now, something else to consider is that most beginners will see some fairly significant changes in their body composition during the first few months of their workouts.

So, let’s assume that our beginner has a fair amount of body fat.

This person will generally see some slow size and strength gains over the first 1-3 months of training.

And this will still occur even though this person isn’t eating enough calories.

However, their gains would typically occur faster (and probably bigger) if they were eating at a calorie surplus.

That being said, as they are stimulating their muscles in a new way, it’s likely they’ll experience some growth anyway.

However, due to the lack of calories these gains will slow down before eventually stopping altogether.

Now, let’s say that our beginner had very low levels of body.

However, they train and eat in the same way (not consuming enough calories).

This beginner will typically see some strength gains during that same 1-3 month period, although these strength gains are more likely to be Central Nervous System adaptations.

Nevertheless, it is highly unlikely that the same person will see much, if any, muscle gain.

If this person continues to train and eat in the same way, they will generally train at the same levels, without being able to progress in terms of weight lifted.

Plus, this person is likely to continue losing body fat, but also muscle mass.

In other words, any benefits gained from the first few months of training will be lost in subsequent months due to a lack of ample calories.


Now, this is when those lack of calories are really going to make a difference to your training and your body.

For me, an intermediate lifter is someone who’s been training for at least a year, makes regular progress, but hasn’t taken their training to elite sport’s level (just yet).

Once again, let’s look at the differences based on body fat levels.

As an intermediate lifter with a lot of body fat, you will be hard-pushed to see any muscular or strength gains.

In fact, it’s more likely that you’ll lose size, strength, as well as body fat.

That being said, you still may not lose all the body fat you want, even though you’re eating at a calorie deficit.

One of the main issues with not eating enough is what it does to your metabolism, as well as your brain.

Firstly, both training and eating can have an impact on your metabolic rate.

Your aim is to keep your metabolism running high, which in turn will burn more calories and body fat during the day.

However, when you’re not eating enough calories, your metabolic rate starts to slow down, thus meaning you’re now burning fewer calories and body fat.

Furthermore, the lack of food can often send your brain into “starvation mode”.

Basically, your brain receives messages from your body stating that you haven’t consumed enough calories, so in effect your body then holds onto fat stores to potentially use for energy later.

And this is why often those last 5-10 pounds are often the hardest to shift for people trying to lose weight.

As for our intermediate lifter who has low levels of body fat, the lack of calories will simply see them lose size and strength rapidly.


This is very simple.

An advanced lifter would never ask this question, LOL, as they have trained long enough and hard enough to realise that they must fuel their workouts and recovery correctly.

And this is one of the main points about eating enough calories if you lift weights.

You’re eventually going to find that your energy levels are shot each and every time you go to the gym.

This will also mean that you’re unlikely to train with the same intensity, plus it won’t be long before you have to probably reduce the weights that you’re lifting.

So, not only are you not eating enough to gain size and strength, you’re now going to lose what size and strength you have because you don’t have the energy to train properly.

This is the bottom line when it comes to lifting weights and not eating enough calories.

What Happens if You Lift Weights But Don’t Eat Enough Protein?

You’re probably aware that protein is your most important macronutrient when it comes to lifting weights.

Basically, protein is required to increase muscle mass, maintain muscle mass, and to aid muscle recovery.

Therefore, if you’re not eating enough protein, it’s much the same effect as not consuming enough calories.

That being said, you can certainly get away with eating at a calorie deficit for a while, as long as you’re consuming enough protein.

This will depend on your current body composition and your overall goals.

However, for most people, you should aim to eat 1-1.6g of protein per pound of body weight.

Nevertheless, even if you are consuming this amount of protein, the lack of calories will eventually catch up with you.

So, you’ll end up tired and fatigued at pretty much every training session, and that’s before you’ve even hit the weights.

Therefore, you will end up losing size and strength, as well as having an adverse effect on your metabolism.

Now, if the reason you’re wondering about calories, protein, and not eating enough, is because you have excess body fat, then it makes sense to lose this first.

Most people would love to build muscle and burn body fat at the same time, although the general principles to achieve either typically work against each other.

Personally, I feel it makes much better sense to eat at maintenance calories and focus on the big compound lifts in the gym.

At least this way you’re eating enough to help with muscle maintenance and muscle growth.

The more lean muscle mass you have, the less body fat you can expect.

Plus, muscle will burn more calories while at rest, thus meaning that you are burning more body fat on a daily basis anyway.

How to Eat More Protein For Muscle Growth (5 Simple Tips)

Final Thoughts

So, I hope you understand that lifting weights and not eating enough calories is likely to cause a number of detrimental effects.

However, this will mainly see you lose size and strength over a period of time.

This is actually made worse by the fact that you also probably won’t have sufficient energy to train effectively.

And this once more will lead to a loss in size and strength.

To make matters even worse, if you’re not getting enough protein, while at a calorie deficit, you’re likely to see this loss of size and strength occur much faster.

While I’m on the subject of protein I recently shared my opinion on the age-old argument about taking 2 scoops of whey protein at once.

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