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Why Doesn’t Protein Fill You Up? (12 Surprising Reasons)

Out of the 3 macronutrients – protein, carbohydrates, and fats – protein is by far the most filling.

So, you may be wondering: why doesn’t protein fill you up?

high-protein steak

Why Doesn’t Protein Fill You Up?

After hours of research, I’ve found 12 common reasons why you may not feel full after consuming protein. These are:

  • You’re not eating enough calories.
  • You’re not eating enough fiber.
  • You’re not getting enough sleep.
  • You’re confusing fullness with cravings.
  • You’re not eating enough whole foods.
  • You’re not eating enough healthy fats.
  • You’re exercising more.
  • You’re consuming too much whey protein.
  • You’re skipping meals.
  • You’re not drinking enough water.
  • You’re not used to a high-protein diet.
  • You’re stressed.

Let’s explore these in more detail.

You’re Not Eating Enough Calories

Hunger is largely controlled by a hormone called ghrelin.

When ghrelin levels are high, you’re more likely to feel hungry and when ghrelin levels are low, you’re more likely to feel full.

There are many different factors which affect ghrelin levels, and one of these is the amount of calories you consume.

While protein does lower ghrelin levels (and thus reduces hunger), you’ll likely have higher ghrelin levels than someone who consumes the same amount of protein as you but consumes more calories overall.

Using apps like MyFitnessPal can be a great way of tracking your daily calories and working out whether you’re eating less calories than you originally thought.

You’re Not Eating Enough Fiber

High fiber foods stretch your stomach and balance hunger hormones, like ghrelin. They typically take a long time to digest too, which keeps you feeling satiated for longer.

If you’re eating a lot of protein but very little fiber, then you may find that you’re feeling hungrier than expected.

Something as simple as adding 100g of green vegetables to each meal can go a long way at keeping the hunger pains at bay.

You’re Not Getting Enough Sleep

Most people require between 7-9 hours of high-quality sleep each night.

Not only is this important for recovery and muscle growth, but research shows that those who don’t get enough sleep have higher ghrelin levels.

For example, in a 2004 study, the subjects who had less than 7.7 hours of sleep had elevated ghrelin.

And as you now know, higher ghrelin levels are associated with an increase in appetite.

If you’re eating a high-protein diet but aren’t feeling satiated, then it’s possible that you aren’t getting enough sleep.

You’re Confusing Fullness With Cravings

It’s important to distinguish between actual hunger and a desire to eat.

Actual hunger is when your stomach is growling and you’re low on energy.

Whereas a desire to eat is when you really want some food to alleviate a certain feeling.

Perhaps you’re bored of eating high-protein food like chicken breast 3 times a day, and you really crave something sweet, like chocolate. In this instance, the feeling is boredom.

Or perhaps you’ve had a bad day at work and are feeling a bit depressed, so you seek some comfort food to cheer you up.

In both these scenarios, you’re not actually hungry but are craving more food to make you feel better.

You’re Not Eating Enough Whole Foods

When you eat a diet that consists mainly of whole foods, like fruit, vegetables, meat, and complex carbohydrates, it’s very difficult to overeat.

This is because our ancestors lived off a whole food diet (otherwise known as the Paleo diet), so we’re wired to eat this way.

As a result, our hunger hormones fluctuate in a more predictable fashion when eating these foods.

If your diet contains a lot of refined sugars and unnatural additives, like MSG, then your hunger hormones will spike and crash in an unpredictable way, leaving you feeling hungry.

By replacing these foods with ‘food from the land’, you’ll often find that your hunger goes away.

You’re Not Eating Enough Healthy Fats

Many people on high-protein diets will reduce their carbohydrate intake.

If you lower your carbs, then it makes sense to increase your intake of healthy fats, assuming you’re not trying to lose weight.

Studies show that healthy fats help slow digestion and increase satiety. By adding healthy fats to your meals, like nuts and olive oil, you’re more likely to feel full when eating a high-protein diet.

You’re Exercising More

Topless man doing a bench press in the gym

If you’re eating a lot of protein, then it’s fair to assume that you’re trying to build muscle.

To do so, you’re probably going to the gym multiple times a week, which increases your calorie expenditure.

Eating the same amount of food you ate before you started exercising will result in a net calorie loss, which can make you feel hungry.

Having healthy snacks like a piece of fruit between can be a great way of controlling your blood sugar levels and hunger.

You’re Consuming Too Much Whey Protein

The first time I ever tried a high-protein diet, I pretty much ate the exact same foods but had 3 protein shakes spread out over the course of the day.

Now, there’s nothing wrong with whey protein, and I still use it to this day. But increasing your protein intake purely through liquid meals, like protein shakes, will often leave you feeling hungry.

This is because whey protein is rapidly absorbed in the body, and as soon as it’s absorbed, your ghrelin levels start to rise.

And as it’s a liquid, your stomach will remain relatively empty which can signal to your body that it needs food.

You’re Skipping Meals

If you want to have stable energy and hunger levels throughout the course of the day, then it’s important to eat regularly and not skip meals.

While I am a fan of intermittent fasting for weight loss, it can lead to hunger, especially while you’re fasting.

Diets such as the OMAD (one meal a day) diet have risen in popularity recently. While they can help with fat loss, they’re not ideal if you’re trying to avoid feelings of hunger.

You’re Not Drinking Enough Water

Experts recommend that you drink around eight 8-ounce glasses of water a day, and

owadays, most people simply don’t drink enough.

There are many downsides to this – one of them being increased levels of ghrelin and hunger.

That’s right – being hungry is often a sign of dehydration!

The next time you feel your stomach growl, then have a cup of water and see if that makes a difference. You’ll be surprised by the results.

You’re Not Used To A High-Protein Diet

Any time you substantially change your diet, it takes time for your body to adjust.

If you’re someone who’s went from a low protein, high carbohydrate diet to a high protein, low carbohydrate diet, then your body will crave carbs for the first few weeks.

This is normal and to be expected, so my advice is to be patient and let your body adjust to your new diet.

Once it gets familiar with your new eating patterns, you’ll often find that your hunger will go away.

You’re Stressed

When you’re stressed, your cortisol levels rise which can increase your appetite.

(This partly explains why people binge eat after a stressful week at work.)

If you are feeling run down, then there are many ways to manage this, like meditation, spending quality time with your family, and going outdoors in nature.

While these may seem insignificant, you’d be surprised at the difference they can make to your mental wellbeing and your hunger levels.


In summary:

  • Protein doesn’t fill you up if you’re not consuming enough calories from a whole food diet.
  • There are other non-diet related factors that can increase appetite, like not enough sleep, stress, and emotional eating.

That’s all for this article, but is Chipotle good after workout? Or does almond milk give you moobs?

Hope this helped!