What Happens if You Don't Eat Enough Protein?

Here are five signs you might need more protein.

Asian woman smiling and looking up while holding a protein bar outside.

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Protein is essential to health. It’s a macronutrient—a nutrient the body needs and uses in large amounts. After all, proteins are needed for every biochemical reaction in the body. They also play essential roles in providing structure and support to cells, helping cells communicate, and protecting the body from viruses and bacteria.

Most people in the U.S. take in enough protein to meet their needs daily, but certain populations have increased protein needs and are at higher risk for inadequate protein intake.

Not taking optimal amounts of protein negatively impacts health in various ways, so eating enough protein is important for health.

Asian woman smiling and looking up while holding a protein bar outside.

SteveLuker / Getty Images

What Is Protein Deficiency?

Having protein deficiency means you're not getting the protein your body needs. This can lead to weakness, stunted growth, and impaired immunity.

Severe protein deficiency can lead to two forms of malnutrition known as kwashiorkor (which can cause edema, or swelling) and marasmus. These types of life-threatening malnutrition are more common among children in developing countries.

Malnutrition

Malnourishment; Undernutrition; Micronutrient-related malnutrition


Malnutrition refers to a lack, excess, or imbalance in a person's intake of nourishment (protein, vitamins, and minerals). It can be caused by not having enough to eat, not getting enough nutrients in the food being consumed, or one's body being unable to utilize the food they eat.

In the U.S. and other developed countries, protein deficiency is rare, especially at severe levels. However, certain groups of people are vulnerable to protein deficiency, such as people with cancer and people in long-term care facilities. People following restrictive diets that cut out sources of protein-rich foods are also at risk of not taking in enough protein.

Signs You're Not Eating Enough Protein

Low protein intake can take a toll on your body and lead to several health effects. Here are a few potential signs of low protein intake.

Muscle Loss

To maintain muscle mass, you need to consume enough protein daily.

You'll lose muscle mass if you don't meet minimum protein requirements. That's because your body will break down your muscle to get the energy it needs.

Even just a little muscle loss can impact your movement or strength.

Weakened Immune System

Proteins make up an important part of the immune system. Adequate protein is critical for producing antibodies, which bind to bacteria and viruses to protect you from getting sick.

Inadequate protein intake can impair immune function. For example, lacking protein might mean antibodies are made in lower amounts. This increases your risk of infections.

Decreased Bone Development and Density

Your bones are made primarily of collagen, a protein type.

For children, low protein intake can cause a reduction in bone development. For older people, not consuming enough protein can negatively affect bone mineral density, which impacts bone strength. This means you can have weaker, more delicate bones.

Studies show that older adults who consume higher amounts of protein have higher bone mineral density and are less likely to experience bone fractures compared to older adults who consume lower protein diets.

Increased Hunger

Besides protein, the other macronutrients are carbohydrates and fat. Of the three, protein is the most satiating, meaning it's best at keeping you feeling full.

If you're not eating enough protein at meals and snacks, you'll likely feel hungry soon after eating. Research shows that, even if you don't realize it, the snacks that you reach for to try to quiet the hunger of a low-protein diet would likely be savory high-protein foods. It's your body's way of trying to stabilize your protein intake.  

Eating protein-rich snacks and meals can help keep you feeling satisfied between meals. It may also help you maintain a healthy body weight.

Compromised Skin and Hair

Low-protein diets can affect the health of your skin and hair, both of which are made with protein.

Protein is critical for the growth and maintenance of healthy hair and skin. Not taking in adequate amounts of the macronutrient can result in side effects like dry skin, premature aging, and thinning hair.

Low protein intake can even trigger telogen effluvium, a condition that leads to excessive hair shedding and hair loss.

How Much Protein Do You Need?

Protein needs vary depending on factors like age, weight, and physical activity levels.

For U.S. adults, the recommended dietary allowance (RDA) for protein is 0.8 grams per kilogram of body weight. That equals 0.36 grams of protein per pound of what you weigh.

However, even though many people think the protein RDA is the recommended optimal intake, it's the minimum amount of protein necessary to prevent muscle loss. This means many people need more protein than that to maintain optimal health.

Protein recommendations include:

  • Experts suggest that physically active people should aim for a daily protein intake between 1.2-2.0 grams per kilogram daily (0.54-0.9 grams per pound), much higher than the current RDA.
  • Some people, like athletes, may need even more protein to maintain muscle mass and support health. For example, some research shows that certain athletes' protein needs can exceed 2 grams per kilogram (0.9 grams per pound).
  • People who are pregnant or breastfeeding, older adults, and those with medical conditions that increase protein needs, like cancer, also have greater protein requirements than the general population.

Still, not everyone should consume high amounts of protein in their diet. For example, too much protein could harm people with kidney disease and other conditions. Talk to your healthcare provider about how much protein you need.

How To Ensure You're Getting Enough Protein

Protein is important to health, and not eating enough can negatively impact your immune system, bones, and more. As such, you'll likely want to make sure you're getting the right amount of protein daily.

Even though protein needs vary significantly based on factors like age, weight, and activity levels, it's relatively easy for most people to cover their protein needs by adding a source of protein to every meal and snack. Fortunately, there are plenty of animal and plant-based protein sources from which to choose.

Animal sources of protein include:

  • Eggs
  • Poultry like chicken and turkey
  • Fish and shellfish
  • Red meat like beef and venison
  • Dairy products like yogurt and cottage cheese
  • Protein powders made with whey and egg whites

Plant-based sources of protein include:

  • Legumes like beans, peas, and lentils
  • Nuts, seeds, and nut butter
  • Soy products like tofu
  • Plant-based protein powders
  • Certain whole grains like quinoa or brown rice

In general, if you eat animal meat, it's healthy to consume a diet that contains both animal and plant-based protein sources. For example, legumes and whole grains are healthy additions to one's diet and great sources of protein. Also, try eating only low amounts of red and processed meat—as too much may lead to a higher risk of heart disease.

If you don't eat animal products, getting adequate amounts of protein on plant-based diets is still possible.

If you're concerned about your protein intake, try adding protein sources to every meal and snack. For example, you could:

  • Add peanut or almond butter to apple slices, then sprinkle the apples with hemp seeds to increase the protein content.
  • Mix plant or animal-based protein powder into your morning oats to make your breakfast more filling.
  • Top your salad with chicken, fish, hard-boiled eggs, or beans.
  • Swap your morning bowl of cereal for a higher-protein option like an egg and vegetable omelet or Greek yogurt topped with pumpkin seeds and berries.

Dietary supplements are minimally regulated by the FDA and may or may not be suitable for you. The effects of supplements vary from person to person and depend on many variables, including type, dosage, frequency of use, and interactions with current medications. Please speak with your healthcare provider or pharmacist before starting any supplements.

A Quick Review

The amount of protein you need can vary based on age, weight, and activity levels. Even though protein deficiency is rare in developed countries like the U.S., some people—especially certain populations like older adults—may not be consuming enough protein daily to promote optimal health.

Not eating enough protein for your specific needs can cause several side effects, from muscle loss to an increased susceptibility to infections.

Fortunately, for most people with the ability to follow well-rounded diets, getting enough protein isn't difficult. Plenty of animal and plant-based protein sources can easily be added to meals and snacks to meet your needs for this important nutrient.

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