What Happens When You Don’t Eat Enough Protein?

Protein is essential to health. It’s a macronutrient—a nutrient that the body needs and uses in large amounts. After all, proteins are needed for virtually every biochemical reaction that takes place in the body. They also play important 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 on a daily basis, but certain populations have increased protein needs and are at higher risk for inadequate protein intake.

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

How Much Protein Do You Need?

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

For U.S. adults, the current recommended dietary allowance (RDA) for protein is 0.8 grams per kilogram of body weight. That’s equal to 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 actually the minimum amount of protein necessary to prevent muscle loss. This means that most people need to take in more protein 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 each day (0.54-0.9 grams per pound), which is 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 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 potentially be harmful for people with kidney disease and other conditions. Talk to your healthcare provider about how much protein you personally need.

Signs You're Not Eating Enough Protein

Severe protein deficiency can lead to two forms of malnutrition known as kwashiorkor and marasmus. Both can cause stunted growth, with kwashiorkor also causing swelling (edema). These types of life-threatening malnutrition are more commonly seen among children in developing countries.

In the U.S. and other developed countries, protein deficiency—especially to such severe levels—is rare. Still, certain people in the US are more at risk for not getting adequate protein.

One example of a population that's at risk for inadequate protein intake is older adults living in nursing homes. People following poorly planned restrictive diets that cut out sources of protein-rich foods are also at risk for not taking in enough protein to support optimal health.

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

Muscle Loss

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

If you don’t meet minimum protein requirements, you'll start to lose muscle mass. That’s because your body will break down your muscle as a way 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 the production of antibodies, a type of protein that binds to bacteria and viruses to protect you from getting sick.

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

Decreased Bone Development and Density

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

For children, low protein intake can cause a reduction in bone development. For seniors, 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. Without the need for as many snacks, 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 to Ensure You're Getting Enough Protein

Protein is important to health, and not eating enough of it 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 on a daily basis.

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 sources of protein 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 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 sources of protein, as per the U.S. Department of Agriculture. Also, try eating only low amounts of red meat and processed meat—as too much may lead to a higher risk of heart disease.

If you don't eat animal products, it's still possible to get adequate amounts of protein on plant-based diets.

If you're concerned about your protein intake, try adding sources of protein 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 some chicken, fish, hard boiled eggs, or beans.
• Swap your morning bowl of cereal for a higher-protein option like an egg and veggie omelet or Greek yogurt topped with pumpkin seeds and berries.

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 taking in enough protein on a daily basis to promote optimal health.

Not eating enough protein for your specific needs can cause a number of 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. There are plenty of animal and plant-based sources of protein that can easily be added to meals and snacks to meet your needs for this important nutrient.