What Happens If You Don't Eat Enough Protein?

Protein is essential for building and repairing tissues, maintaining muscle mass, supporting the immune system, and performing many other important functions in the body.

If you consistently do not eat enough protein, your body may struggle to perform these functions optimally. The effects can range from slower recovery and difficulty building muscle to loss of muscle mass and, in severe cases, symptoms of protein deficiency.

Fortunately, most people can avoid inadequate protein intake by eating a varied diet that includes sufficient protein-rich foods.

In this guide, we will explore what happens when you do not eat enough protein, the signs that your intake may be too low, and how to increase your protein consumption.

Why Does Your Body Need Protein?

Protein is made up of amino acids, which your body uses as building blocks for many different structures and processes.

Your body needs protein to:

• Build and repair muscle tissue.
• Maintain bones, skin, hair, and connective tissue.
• Produce enzymes and hormones.
• Support the immune system.
• Transport substances throughout the body.
• Maintain and repair cells.

Because your body constantly breaks down and replaces proteins, you need to consume protein regularly through your diet.

Learn more about the role of protein in muscle growth in our guide: Why Protein Is Important for Building Muscle.

1. You May Struggle to Build Muscle

One of the most noticeable effects of insufficient protein intake is difficulty building muscle.

Resistance training provides the stimulus for muscle growth, but your body also needs amino acids to repair and build new muscle proteins.

If you consistently consume too little protein, your body may not have enough amino acids available to maximize muscle protein synthesis.

This can make it harder to:

• Gain muscle mass.
• Recover from workouts.
• Increase strength.
• Adapt to resistance training.

Protein is therefore an important part of any muscle-building program.

2. You May Lose Muscle Mass

When protein intake is insufficient, the body may break down existing muscle tissue to obtain amino acids.

This can become particularly important during:

• Calorie restriction.
• Weight loss.
• Periods of inactivity.
• Illness or recovery.
• Older age.

Eating enough protein and performing resistance training are important strategies for maintaining muscle mass throughout life.

3. Your Workout Recovery May Be Slower

Exercise creates stress on your muscles. After training, your body needs to repair and adapt to this stress.

Protein provides the amino acids required for this repair process.

If your protein intake is too low, you may find that recovery becomes more difficult, particularly when combined with intense or frequent training.

You may experience:

• Longer recovery periods.
• Persistent muscle soreness.
• Difficulty maintaining training performance.
• Reduced ability to progress in your workouts.

4. You May Have More Difficulty Maintaining Strength

Strength is influenced by many factors, including nervous system adaptations, muscle size, technique, and training experience.

However, maintaining muscle mass is an important part of maintaining physical strength.

If inadequate protein intake contributes to muscle loss, your ability to maintain or increase strength may eventually be affected.

5. You May Feel Hungrier

Protein is generally considered one of the most satiating macronutrients.

Eating enough protein may help you feel fuller after meals and make it easier to control your appetite.

If your diet is very low in protein, you may find yourself feeling hungry more frequently.

This can make maintaining a calorie deficit more difficult if your goal is fat loss.

6. Your Body May Have More Difficulty Repairing Tissues

Protein is required for the maintenance and repair of tissues throughout your body.

When protein intake is consistently inadequate, the body may have fewer resources available for normal tissue repair.

This is particularly important during periods when your body is under increased stress, such as after an injury or during recovery from illness.

7. Your Immune System May Be Affected

Protein and amino acids play important roles in immune function.

Severe protein deficiency can impair immune function and increase vulnerability to illness.

For most healthy people in developed countries, severe protein deficiency is uncommon. However, consistently eating an inadequate diet can still contribute to poor overall nutrition.

8. You May Experience Hair, Skin, or Nail Changes

Your hair, skin, and nails contain proteins, including structural proteins such as keratin and collagen.

Severe or prolonged nutritional deficiencies can affect these tissues.

Possible changes may include:

• Hair becoming thinner or weaker.
• Changes in skin health.
• Weak or brittle nails.

These symptoms can have many different causes, so they should not automatically be attributed to low protein intake.

9. You May Feel Weak or Tired

Low energy can have many causes, including inadequate sleep, insufficient calorie intake, stress, illness, and nutritional deficiencies.

Inadequate protein intake may contribute to weakness, particularly if it leads to loss of muscle mass or occurs as part of an overall inadequate diet.

If you experience persistent or unexplained fatigue, it is important to discuss it with a healthcare professional rather than assuming protein is the cause.

How Much Protein Do You Need?

Your protein requirements depend on your body weight, age, activity level, and goals.

People who exercise regularly or want to build muscle generally need more protein than sedentary individuals.

A common range for people who perform resistance training is approximately:

1.6–2.2 grams of protein per kilogram of body weight per day.

For example, a person weighing 70 kg might aim for approximately 112–154 grams of protein per day when focusing on muscle growth.

However, individual requirements vary.

Use our Protein Need Calculator to estimate your personal daily protein needs.

How Can You Tell If You Are Not Eating Enough Protein?

There is no single symptom that proves you are not consuming enough protein.

However, possible signs of inadequate protein intake may include:

• Difficulty gaining or maintaining muscle.
• Slow recovery from exercise.
• Unexplained muscle loss.
• Frequent hunger.
• Weakness.
• Reduced strength.
• Hair, skin, or nail changes in cases of significant deficiency.

These symptoms can also have many other causes, so they should not be used to diagnose protein deficiency on their own.

What Is Protein Deficiency?

Protein deficiency occurs when the body does not receive enough protein to meet its physiological needs.

Severe protein deficiency is relatively uncommon in many developed countries but can occur in situations involving severe malnutrition, certain illnesses, or conditions that affect nutrient absorption.

Severe deficiency can have serious consequences, including:

• Loss of muscle mass.
• Weakness.
• Impaired immune function.
• Poor wound healing.
• Edema or swelling.
• Growth problems in children.

Severe protein deficiency requires medical attention and should not be treated simply by taking protein supplements without professional guidance.

How to Increase Your Protein Intake

If you are not eating enough protein, you can usually increase your intake gradually by adding protein-rich foods to your regular meals.

Simple strategies include:

• Add eggs to breakfast.
• Choose Greek yogurt as a snack.
• Add beans or lentils to soups and salads.
• Include tofu or tempeh in plant-based meals.
• Choose fish, chicken, or lean meat with main meals.
• Add cottage cheese to snacks or meals.
• Use a protein shake when convenient.

The goal is not necessarily to eat enormous amounts of protein. Instead, focus on consistently reaching an appropriate amount for your individual needs.

Best High-Protein Foods

There are many nutritious foods that can help you increase your protein intake.

Animal-Based Protein Sources

• Chicken breast.
• Turkey.
• Fish.
• Eggs.
• Greek yogurt.
• Cottage cheese.
• Milk.
• Lean beef.

Plant-Based Protein Sources

• Tofu.
• Tempeh.
• Lentils.
• Beans.
• Chickpeas.
• Peas.
• Seitan.
• Soy products.

Different protein sources have different amino acid profiles and protein quality. Combining a variety of foods can help you obtain a broad range of essential amino acids.

Use our Protein Combining Score Calculator to explore how different foods can be combined to improve the overall protein quality of your meals.

How to Get Enough Protein on a Vegetarian or Vegan Diet

People following vegetarian and vegan diets can obtain enough protein, but they may need to pay closer attention to food choices and total protein intake.

Useful protein sources include:

• Tofu and tempeh.
• Soy milk.
• Beans and lentils.
• Chickpeas.
• Peas.
• Seitan.
• Pea and soy protein powders.
• Nuts and seeds.

Eating a variety of protein sources throughout the day can help provide all the essential amino acids your body needs.

Learn more about protein quality in our article Protein Quality Explained.

Getting Enough Protein During Weight Loss

Protein becomes especially important during weight loss because a calorie deficit can increase the risk of losing muscle mass.

To support muscle retention during fat loss:

• Consume enough protein.
• Perform regular resistance training.
• Avoid unnecessarily aggressive calorie deficits.
• Spread protein intake across multiple meals.
• Choose nutrient-dense foods.

Use our Protein Need Calculator to estimate an appropriate protein target for your goals.

How to Distribute Protein Throughout the Day

Instead of eating almost all your protein in one meal, consider spreading it throughout the day.

For example, someone with a daily protein target of 120 grams could divide it into four meals:

This is only an example. Your ideal protein distribution will depend on your daily target, body size, schedule, and preferences.

Protein and Older Adults

Maintaining adequate protein intake becomes increasingly important with age because muscle mass naturally tends to decline over time.

This age-related loss of muscle is known as sarcopenia.

Regular resistance training and adequate protein intake can help support muscle maintenance as you age.

Older adults may also benefit from paying particular attention to the protein content of individual meals rather than consuming very small amounts throughout the day.

Protein and Exercise Recovery

If you exercise frequently, your protein requirements may be higher than those of someone who is sedentary.

Protein supports recovery by providing amino acids that your body can use to repair muscle tissue after exercise.

For athletes and active individuals, insufficient protein combined with high training volume may make it more difficult to recover and adapt.

However, protein is only one part of recovery. You should also prioritize:

• Enough sleep.
• Adequate calories.
• Sufficient carbohydrates.
• Rest days when needed.
• Proper hydration.

Frequently Asked Questions

What happens if you do not eat enough protein?

Insufficient protein intake can make it harder to build and maintain muscle and may impair recovery. Severe deficiency can cause more serious problems, including weakness, muscle wasting, and impaired immune function.

Can low protein intake cause muscle loss?

Yes. Inadequate protein intake can contribute to muscle loss, particularly during calorie restriction, inactivity, illness, or aging.

How do I know if I am eating enough protein?

Calculate your estimated daily protein needs based on your body weight, activity level, and goals. You can use our Protein Need Calculator as a starting point.

Can I get enough protein from plants?

Yes. A well-planned plant-based diet can provide enough protein. Foods such as tofu, tempeh, legumes, soy products, and protein-rich grains can contribute significantly to your intake.

Does low protein make you tired?

Severe protein deficiency can contribute to weakness and poor health, but tiredness has many possible causes. If you experience persistent fatigue, consult a healthcare professional.

Can you eat too little protein while building muscle?

Yes. If your protein intake is consistently too low, you may not maximize your ability to repair and build new muscle tissue, even if your training program is effective.

Related Articles

• How Much Protein Do You Need Per Day?
• Why Protein Is Important for Building Muscle
• Can You Eat Too Much Protein?
• Protein Timing: Does It Matter?
• Protein Quality Explained
• Best Sources of Protein
• Amino Acids Explained

Conclusion

Not eating enough protein can make it harder to build and maintain muscle, recover from exercise, and support normal bodily functions. Severe protein deficiency can have much more serious health consequences.

For active individuals, athletes, and people trying to build muscle, getting enough protein should be a priority. However, protein is only one part of a healthy diet. Your body also needs sufficient calories, carbohydrates, healthy fats, vitamins, minerals, fiber, and fluids.

The best approach is to find a protein intake that matches your individual needs and consistently include protein-rich foods in your meals.

Use our Protein Need Calculator to estimate your daily protein needs, and use our Protein Combining Score Calculator to explore different food combinations and improve the overall protein quality of your meals.