4 Things That Can Happen When You Don’t Get Enough Protein

Of the three macronutrients (carbs, fat, protein) our bodies need, protein seems to hog most of the spotlight. (Unless we’re talking about keto, of course.) Though long regarded as something only bodybuilders needed to worry about, protein supports general health and well-being in a number of ways. Fail to get enough and you’ll face serious consequences.

Here’s the thing: while true protein deficiency is pretty rare in the U.S., not getting enough protein for your body to thrive is more common than you’d think. In fact, some analyses suggest roughly one-third of adults over 50 may fall below the protein RDA. And the consequences can sneak up on you in ways you might not expect.

How Protein Benefits Your Body

Muscle isn’t the only tissue in your body protein helps build. In fact, protein contributes the ingredients (in the form of amino acids) needed to keep all the tissues and cells in your body healthy. “Protein provides the structural basis for not only muscle tissue, but also red blood cells, tendons, hormones, enzymes, and antibodies,” says Kelly Pritchett, Ph.D., R.D., director of sports nutrition at Central Washington University.

In other words: Protein keeps all the cells and tissues in your body humming along. Think of it like the building blocks your body uses to repair, maintain, and rebuild just about everything—from the muscles you use to climb stairs to the enzymes that help you digest your lunch.

Your body also uses this key macronutrient for other cool things, including:

• transporting nutrients throughout your body
• keeping skin and hair healthy (ever notice brittle nails or thinning hair when you’re not eating well?)
• as a last-ditch energy source when other fuel sources are depleted (like during endurance exercise)
• producing hormones that regulate everything from mood to metabolism
• supporting wound healing and tissue repair

The Protein Quality Factor

Not all protein is created equal, by the way. Animal proteins (like chicken, fish, eggs, and dairy) are considered “complete” proteins because they contain all nine essential amino acids your body can’t make on its own. Plant proteins can be complete too—think soy, quinoa, and hemp seeds—but many need to be combined (like beans and rice) to give you the full amino acid picture.

This matters because your body uses protein more efficiently when it gets all those essential amino acids together. If you’re vegetarian or vegan, don’t stress—just aim to eat a variety of plant-based protein sources throughout the day.

How Much Protein You Need

Since all the cells in your body constantly use and break down protein, you need a steady intake of it to ensure your cells maintain their structure and function, says Michael D. Roberts, Ph.D., director of the Molecular and Applied Sciences Laboratory at Auburn University.

Research from the National Institutes of Health confirms that most Americans eat more than the minimum daily recommendation of protein. (That’s 46 grams a day for women and 56 grams a day for men, according to the National Institutes of Health.)

Read More: 8 Surprising Sources Of Protein

However, here’s the catch: those minimums are just that—minimums. They’re designed to prevent deficiency, not to help you thrive. Some groups—like the International Society of Sports Nutrition—suggest adults aim higher. (Like closer to 95 grams per day for a 150-pound person.)

That’s easier said than done—especially if you have certain dietary restrictions. One review published in The Journal of the American Osteopathic Association warns that cutting animal products from your diet can put you at a higher risk of protein deficiency if you’re not careful about getting enough plant-based alternatives.

Your Needs Change as You Age

Here’s something that surprises a lot of people: as you get older, you actually need more protein, not less. Research from Stanford Lifestyle Medicine shows that adults over 50 should aim for 1.0 to 1.2 grams of protein per kilogram of body weight daily—compared to the standard 0.8 grams for younger adults.

Why the increase? Your body becomes less efficient at using protein as you age (scientists call this “anabolic resistance”). So even if you’re eating the same amount of protein you did in your 30s, your body might not be getting the same benefits.

For adults 65 and older, some experts suggest aiming even higher—between 1.2 and 2.0 grams per kilogram of body weight, especially if you’re active or recovering from an illness.

What Happens When You Don’t Get Enough Protein

Given everything protein does for your body, falling short can have a few not-so-pleasant side effects. Though true deficiency (which is associated with serious issues like liver disease) is uncommon in the U.S. these days, falling short on your needs can lead to a slew of other problems.

Here are four big ones to watch out for:

1. Muscle Loss

“When we don’t get enough protein, the lack of amino acids leads to increased breakdown of body proteins,” Pritchett says. One of the biggest victims: muscle tissue.

If you strength train regularly (the CDC recommends training all muscle groups at least twice per week), you already break down muscle more than non-lifters. That means it’s especially important to keep your protein intake in the black. After all, your body needs plenty of building blocks to rebuild and repair that broken-down muscle tissue so it can grow back bigger and stronger.

Even if you’re not a gym-goer, though, you still need to consume adequate protein to maintain the muscle you have. One American Journal of Clinical Nutrition study, for instance, found that when elderly women ate a low-protein diet for nine weeks, they lost a whopping 14 percent of their muscle mass.

Lose any amount of muscle and you may find that once-mundane daily tasks—like walking up a flight of stairs or getting out of a chair—become more challenging. In fact, age-related muscle loss (a.k.a. sarcopenia) is one of the main reasons older adults can’t move around without help, according to a Current Opinion in Rheumatology review.

The Numbers Are Eye-Opening

Research from the NIH shows that starting around age 30, we naturally lose 3-5% of our muscle mass per decade. By the time you hit 80, sarcopenia affects up to half of older adults. The good news? Getting enough protein (combined with regular strength training) can help slow this process significantly.

And if you’re trying to lose weight, here’s something important to know: during weight loss, some of the weight lost can come from fat-free mass, and the fraction varies by factors like starting body fat, diet, and training. That’s why protein becomes even more critical when you’re cutting calories.

2. Lowered Immunity

Aside from muscle, the amino acids in protein also help build and maintain healthy immune cells. Eat too little protein and you risk weakening your immune system, making it hard for you to fight off infections.

Animal research, like this Journal of Infectious Diseases study, shows that mice given very low-protein diets exhibit more severe flu symptoms—the result of having lower levels of antibodies, compounds that fight infection. However, once the mice were given higher-protein diets, their ability to fend off the virus improved.

Signs Your Immune System Might Be Struggling

If you find yourself catching every cold that goes around the office or noticing that cuts and scrapes take forever to heal, your protein intake might be worth examining. Your body prioritizes protein for essential functions—and when supplies are low, immune function can take a backseat.

Other signs to watch for:

• Frequent infections or illnesses
• Slow wound healing
• Feeling run down more often than usual
• Longer recovery times after workouts or minor injuries

3. Weakened Bones

Calcium and vitamin D typically get all the credit for building strong bones. However, protein is key for keeping bones healthy, too.

In fact, as long as calcium levels are solid, higher protein intake is associated with higher bone mineral density (a determinant of bone health), slower bone loss, and lower hip fracture risk in older adults, per one 2018 Osteoporosis International review.

Think of it this way: calcium and vitamin D are like the bricks that build your bones, but protein is the mortar that holds everything together. You need all three working in harmony.

The Protein-Bone Connection

Your bones are constantly being broken down and rebuilt (just like muscle), and protein provides the structural framework for this process. When protein is scarce, your body might not be able to keep up with bone maintenance, potentially leading to:

• Lower bone mineral density over time
• Increased fracture risk, especially in older adults
• Slower healing after bone injuries

4. Increased Hunger

Meals that contain protein leave you better satiated than those that rely on carbs and fat alone. (This is good news for anyone striving to lose body fat or maintain a healthy weight.)

Skimp on this macronutrient, though, and you may find yourself at the vending machine (or fridge) shortly after meals.

Case in point: Per one 2007 Journal of Nutrition study, men reported higher hunger ratings while on a low-protein diet than they did while on a high-protein diet. If greater feelings of hunger lead to increased food consumption in the long run, weight gain can certainly follow.

Why Protein Keeps You Full

There’s actually some cool science behind why protein is so satisfying. When you eat protein:

• It takes longer to digest than carbs, keeping you fuller longer
• It triggers the release of hormones that signal fullness to your brain
• It has a higher “thermic effect,” meaning your body burns more calories just processing it
• It helps stabilize blood sugar, preventing those energy crashes that send you reaching for snacks

So if you’re constantly hungry between meals despite eating what feels like enough food, take a look at your protein intake. Adding even a few extra grams to each meal might make a noticeable difference.

How To Make Sure You Get Enough Protein

Now that you (hopefully) appreciate the importance of protein for your health and fitness, make sure your intake is solid.

Aim for the International Society of Sports Nutrition‘s recommendation of 1.4 to 2 grams of protein per kilogram of body weight per day.

Read More: 6 Questions To Ask Before Buying A Protein Powder

To figure out what that means for you, divide your weight (in pounds) by 2.2 to get your weight in kilograms. (If you weigh 150 pounds, that’s approximately 68 kilograms.) Then, multiply that number by 1.4 to calculate your minimum daily needs. (If you’re 150 pounds, that’s a minimum of 95.2 grams per day.)

Spread It Out Throughout the Day

To hit that number, try to consume at least 25 grams of protein at every meal. (You’ll want to incorporate it into your snacks, too.) Here’s what 25-30 grams looks like in real food terms:

• 4 ounces of chicken breast (about 26 grams)
• 1 cup of Greek yogurt (about 17-20 grams) plus a handful of nuts
• 3 eggs plus some cheese (about 24 grams)
• A scoop of protein powder (typically 20-30 grams depending on the brand)

When Supplements Make Sense

If you’re struggling to hit your protein goals through food alone—whether due to a busy schedule, dietary restrictions, or just not feeling super hungry—protein supplements can be a convenient way to fill in the gaps. Options like whey protein, plant-based powders, and protein bars make it easier to get quality protein on the go.

Still stuck? Check out these nine easy ways to increase your protein intake.