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

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In this article I share what sports science & nutrition research have found regarding the effect that different amounts of dietary protein have on muscle & strength training.

Your body needs a certain amount of daily protein just to take care of all sorts of essential system tasks besides building muscle. (1)

And more intensive athletic activities like weightlifting further increases your body’s dietary protein need. (2)



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Science resources included

As is my custom here on heydayDo, I will provide links to all of the relevant sports science & medical resources, clinical studies, and nutritional data used in this article.



What’s next

I’ll provide the sport nutrition experts’ answer(s) to the question I posed in the title in just a bit.

As with many things in life, you’ll see that exactly “what happens” in an insufficient protein scenario depends on a few important things, so we need to get into those too.


The downside of inadequate protein

We’ll also look at what the potential side effects & health issues are that come with a diet that doesn’t have enough protein in it.


And the upside of getting enough protein

And on the flip side of that, I’ll share what nice benefits weightlifters, athletes, other workout warriors, & even sedentary people receive from just making sure that their bodies’ protein needs are met.

And that’s not hard to do, as you’ll learn (if you didn’t know that already.)


Attending to the elephant in the room

But before we can talk about any of this, there’s something we have to clarify just so we’re all good and on the same page.

We need to address a fundamental question, which is simply this:

How much is “enough” protein?


So we’ll do that right after answering our biggie first.


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

Weightlifting increases the amount of protein a person needs in order to maintain nitrogen balance, a requirement for being healthy.

A negative nitrogen balance caused by inadequate dietary protein can cause several health problems including muscle loss, fatigue, slow healing, edema, & insomnia.


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What does “enough” protein mean?

It’s important that we have a good understanding of just how much “enough” protein actually is before we can get into anything else, so let’s do that.


Bottom line protein for weightlifters

I’ll give you the recommended daily dietary protein amounts here & now.

The detailed (& medically-referenced) reasoning immediately follows, which you can dive into or skip ahead & just take my word for it . 😜


For those engaged in intense exercise like weightlifting or athletics, this is your per day protein requirement range:

1.5 to 2.0 grams of protein per kilogram of body weight. (3)


(In case you didn’t know, 1 kilogram = 2.2 lb. Here’s a conversion calculator you can use if need be.)

That daily protein requirement comes out to about 0.7 – 0.9 grams of protein per pound of our body weight.

So with me around 180 lb., that equals a daily range of 0.7 x 180 (126 grams) to 0.9 x 180 (162 grams).


For those who aren’t lifters or people who don’t exercise much, this is their per day protein requirement range:

0.8 to 1.3 grams of protein per kilogram of body weight. (4)



Science behind the protein amounts

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Here’s where you’ll find out who comes up with these daily dietary protein requirements, and why these amounts are what they are.


Lots of numbers out there

Searching Google for “how much protein do I need if I lift” or something similar will shower you with all sorts of recommendations.

And that can get confusing, since some of the protein amounts you’re looking at seem to contradict each other.

No worries, making sense of this stuff is well within your grasp.

If I can do it, so can you.


Legitimate numbers from legitimate authorities

There are only a few organizations that have the clout to issue dietary recommendations like how much protein should I eat to the rest of us:


Top medical websites use their numbers

When you’re on a legitimate medical website like Healthline or Mayo Clinic, the daily dietary protein amounts they’ll quote you are taken from one of those 3 organizations.


Fact-driven fitness & nutrition info sites do too

And when you’re visiting a blog (like this one 😉) whose author firmly believes in the equation:

Medical & Sports Science > Bro Science


…the daily dietary protein numbers they’ll quote you will be from one of those 3 nutritional authorities as well.


Bottom line on legitimate sources

So obviously, the per day protein range for weightlifters I gave you earlier came from one of those esteemed organizations too, the International Society of Sports Nutrition to be exact.


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And the right number for us depends

Daily protein needs vary from person to person as you could probably tell, looking at those two sets of number ranges earlier.

How much protein we each need depends on things like:

  • overall diet & caloric intake;
  • amount of physical activity;
  • type of exercise;
  • level of workout intensity while training. (5)


So it’s pretty easy to see that protein requirements for those of us who are strength training &/or athletes are quite a bit higher than for the majority of the population that sits around most of the time. (6)


A lot of sports nutrition research has been done on protein and its effect on athletic performance, muscle-building, & strength increases.

I’m talking hundreds of clinical research trials involving tens of thousands of athletes, recreational weightlifters, & others. (7)


There’s a mountain of evidence and therefore the facts from sports science are pretty dang solid.


Enough protein for a lifter per day

Say you are:

  • a consistent weightlifter
  • an endurance athlete (swimmer, runner), or 
  • a competitive sports athlete 

Then your workout/training level is considered intense, and so your daily protein needs will be met within that range of 1.5 – 2g of protein/kg (0.7 – 0.9g/lb.) of body weight.


Summary of what enough protein is

So now we weightlifters know how much protein is considered enough to satisfy our body’s need in order to keep it healthy & humming along.

In the next section we’ll look at what can happen if you don’t hit those numbers on a regular basis.



Side effects of a low-protein diet

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As I mentioned back at the beginning of the article, there are several health problems that could occur to someone who doesn’t get an adequate amount of protein in their diet.

By the way, these side effects affect regular sedentary people as much as they impact lifters & athletes.


Inadequate protein & the athlete/lifter

Let’s start off with a quote from the International Society of Sports Nutrition, taken from their Exercise & Sports Nutrition Review:

“If an insufficient amount of protein is obtained from the diet, an athlete will maintain a negative nitrogen balance which can increase protein catabolism and slow recovery. 

Over time, this may lead to lean muscle wasting and training intolerance.”


“Protein catabolism”

This is a normal function most of the time, where protein we take in is broken down into amino acids for use throughout our bodies. (8)

This provides nitrogen balance to our bodies, a critically important factor for our good health. (9)

The problem arises when we’re not taking in enough protein but meanwhile, our body is continuing to break down protein at an increased rate, thanks to our intense workouts.

This creates the negative nitrogen balance in our bodies I described earlier, a state where catabolism (breakdown) exceeds anabolism (re-building). (10)


“Muscle wasting”

Also known as muscle atrophy, it’s when you’re losing your muscle mass.

Say there’s not enough protein coming into your body from your diet and it goes catabolic.

Your body will then start using your muscle and break it down for use in order to maintain all of your essential metabolic systems & processes. (11)

Medical studies have shown several times that a low-protein diet accelerates muscle loss.

As medical publisher Healthline writes

“Loss of muscle mass is one of the first signs of inadequate protein intake.” (12)



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“Training intolerance”

This term stands for a series of symptoms both physical & mental that seriously affect the athlete’s performance for the worse.

It’s similar in meaning to the word I use that you may be familiar with too: overtraining.

I describe the condition & its cure in my article here on heydayDo, The Recovery Benefits Of Taking A Week Off From The Gym.

Courtesy of ACE (the American Council on Fitness), here are a few of those undesirable symptoms:

  1. decreased performance
  2. increased perceived workout effort
  3. excessive fatigue
  4. chronic injuries
  5. metabolic imbalances
  6. several more too (13)


Another poor protein side effects list

Courtesy of STACK (the excellent fitness, training, & nutrition resource for high school & collegiate athletes), here’s their list of unsavory side effects caused by a pattern of inadequate daily protein:

  1. low energy;
  2. loss of muscle;
  3. weakened immune system;
  4. edema (water bloat);
  5. blood sugar problems. (14)


And yet another…

This list is provided by TheHealthy.com, a large, general population-oriented health website:

  1. food cravings increase;
  2. metabolism slows;
  3. lose mental sharpness;
  4. injuries don’t heal as well;
  5. become at-risk for anemia;
  6. nails & hair get brittle.


Bottom line: 
Meeting your daily requirement of protein while you’re weight training is a heck of a lot better than dealing with all of those potential problems I just mentioned, as you’ll read below.




Protein benefits for the lifter & athlete

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Assuming you hit your daily protein number on a regular basis, it can provide these benefits:

  • help increase fat-free mass (muscle) & strength (15)
  • help repair & strengthen muscle damage from workouts (16)
  • curb food cravings & keep you full longer (17)
  • boost metabolism & calorie burning (18)
  • help lower blood pressure & cholesterol (19)
  • help maintain weight loss (20)


Bottom line: 
Eating enough protein seems like a no-brainer at this point. Over here, lots of good stuff. Over there, misery.



You don’t need to eat a ton of food

Despite what bro science you may hear at the gym or read online…

…there’s no proven benefit to consuming more daily protein than the range recommended for weightlifters & athletes we reviewed earlier, 1.5 – 2 grams of protein per kilogram of bodyweight.

It’s been shown a number of times in sports performance studies that no additional muscle gains or strength increases can be had by pounding protein above that range. (21)

In fact, there are downsides to eating excess protein:

  • excess protein is stored as fat
  • all of its amino acids are lost & peed out unused (22)


An easy way to get to your protein number

Let’s take a 150 lb. weightlifter whose daily protein requirement range comes out to:

  • 0.7 grams x 150 lb. = 105 grams
  • 0.9 grams x 150 lb. = 135 grams

So, their range is between 105 to 135 grams per day.

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Here’s a quick, off-the-top-o’-me-head example of how easy it is to hit that range, from breakfast to beddy bye:

* 3 lg. eggs & 2 pieces of whole-grain Ezekiel bread: 27 grams

* A peanut butter sandwich, using the same bread & Kirkland peanut butter or Nuttzo: 16 grams

* A scoop of protein powder after your workout, in a shaker bottle + water: 22 grams

* 5 oz. chicken breast, 1 serving organic brown rice = 37 grams

* 1 scoop casein powder with water at bedtime: 22 grams

(Chicken & rice data from fatsecret.com)


There’s 124 grams of protein right there.

Eat all the vegetables & fruit you want since they have minimal protein in them.

There are tons of substitutions possible here of course.

Swap nonfat yogurt for the peanut butter sandwich for instance, or salmon for chicken, quinoa for rice, etc.


My point being: it’s not real hard to get within the healthy range of our daily protein needs.



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Protein FAQ

Here are answers to a few other commonly asked questions regarding the important roles diet & protein have in achieving workout success.


Can you still gain muscle if you don’t eat a lot?

Building muscle is more difficult than normal but still possible, even if your daily calorie count is low &/or you’re in a calorie deficit. (27)

Here are a few tips to improve your odds of success:

* do strength training regularly, since it can build muscle all on its own. (23)

* keep protein intake high enough, since research has shown high-protein diets even during calorie deficits boost muscle gain. (24)

* spread your protein throughout the day, but shoot for at least 1 meal with 30 grams in it. (25)


What happens if you work out but don’t eat enough?

A lack of sufficient calories for someone who is exercising regularly can lead to issues very similar to those associated with overtraining. (26)

Below are a few symptoms a poor diet can cause, courtesy of cheatsheet.com, that really do look like classic overtraining syndrome signs.

  • Weight loss program stalls
  • Hormonal imbalance
  • Muscle loss but fat gain
  • Exhaustion
  • Poor workout recovery
  • Irritability
  • Insomnia


Bottom line: Eating a little bit more food in order to fuel our workouts is a nice & easy “price to pay” in order to avoid all those health problems & mental anguish.



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Wrapping Up

I hope that my article on the importance of getting enough protein if you’re a lifter or athlete is useful to you, and I wish you well on your fitness journey.

Let’s go.

– greg

June 2021


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About heydayDo

heydayDo author Greg Simon
Hi I’m Greg Simon. Fitness training & nutrition researching since 1982. Organic food & wine grower. Surfer. Congenital heart disease survivor (so far). Read more…
heydayDo is my “fitness after 50” website that’s about embracing the physically active lifestyle as we get older.
I write about the fitness and health research I’ve found concerning the quality of life benefits that exercise and good nutrition provide.
When I get curious about something, I’ll dig into whatever sports science & medical facts there are on the topic to learn what’s real & what’s only hype. I also post my experiences product-testing & evaluating home gym equipment & fitness supplements.
 It’s an information-sharing, personal opinion blog of mine.
So if you’re looking for medical or nutritional advice, please consult with your doctor or health professional for that, since heydayDo does not provide medical advice.