Protein is a cornerstone of healthy eating and weight loss and is readily available in many of the foods you eat, including poultry, meat, dairy, fish, eggs, legumes, nuts, seeds, soy and even whole grains. Research shows higher-protein meals or snacks can also help reduce hunger and extend the feeling of satiety.
The recommended daily allowance (RDA) for men ages 19–50 is 56 grams per day, and it’s 46 grams per day for women. To get a more specific recommendation for what you need, you can calculate it based on your body weight, says Lindsey Kane, RD. “Generally speaking, you need .8 grams of protein per kilogram of body weight (which is about .4 grams per pound of body weight).” This translates to about 56 grams of protein for someone who weighs 154 pounds. You can track your protein intake with an app like MyFitnessPal and also pay attention to the following signs you might not be getting enough in your diet:
Protein is made up of amino acids, which are essential for building muscle. This means that if you’re not getting adequate protein, your muscle mass could suffer. “You might notice this as decreased strength, change in weight or even how your clothes are fitting,” says Randy Evans, RD.
In addition to calcium, research shows a protein-rich diet is beneficial for overall adult bone health. “Without sufficient protein to provide energy to our organs and brain, the body will look for other sources, and one place it borrows from is skeletal muscle tissue,” says Cheryl Mussatto, RD, author of “The Nourished Brain,” and “The Prediabetes Action Plan and Cookbook.” “If you are consistently running low on protein, over time, your bones will be susceptible to injuries such as stress fractures and breaks.”
Have you snapped at your significant other or the guy at the coffee shop who wrote your name wrong? “Irritability is one of the signs of low protein,” says Jamie Hickey, a registered dietitian and personal trainer. “By mitigating the effect of carbohydrates [that can spike blood sugar], slow-digesting protein helps keep your mood stabilized.”
If you’re always under the weather, a lack of dietary protein could be to blame. “Protein is a building block of antibodies that are produced by our immune system, helping us fight off bacteria and viruses,” says Mussatto, who adds that now is a super important time to be mindful of protein consumption with cold and flu season lingering. “A diet deficient in protein also results in a reduction in T cells, which fight off germs and enhance our immune system.”
When protein is lacking, nails can become brittle — breaking off easily — while your hair not only loses its luster, but also may stop growing, says Mussatto. Too little protein shifts the body’s focus from growing strong nails and hair to conserving protein.
In more severe cases of protein deficiency, you may not be able to adequately repair injuries or wounds. “Many times our protein needs are increased above our baseline following certain events, including surgeries, infections or injuries,” says Melissa Macher, RD. Similar to becoming more susceptible to stress fractures, you’re also prone to slower healing. “It’s especially important to check with your doctor or dietitian after these big events to determine your specific protein needs and optimal intake.”
We all know what it’s like to experience a craving, but a prime sign you may be protein deficient is if you find yourself heading back to the refrigerator or pantry time and time again. “Without sufficient protein intake, you may not experience fullness,” says Emily Danckers, MS, RD. “This can lead to endless snacking trying to fill the void of hunger.”
It’s normal for hunger levels to fluctuate; for example, you might be hungrier after a hard workout than on a recovery day. However, if you find you can’t seem to get full or feel satisfied regularly from your meals and snacks, it might be a sign you need to incorporate more protein. “The body digests protein more slowly than carbohydrates (which give us quick energy), so it’s a good idea to include a protein source at each meal and snack for a more sustained energy level and satiety,” says Macher.
Inadequate protein can slow metabolism, which affects erythropoietin (EOP) hormone production — critical to the production of red blood cells. This can result in anemia, a condition where you lack enough healthy red blood cells to carry oxygen to the body’s tissues. “Reduced dietary intake of protein may lead to mild-to-moderate anemia,” says Katherine Kimber, RD. Symptoms include fatigue, pale skin, shortness of breath (especially when exercising) and dizziness. If you’re experiencing any of these issues, it’s a good idea to speak with your doctor.
How are your daily energy levels overall? Do you find yourself having an energy slump (or two) throughout the day? “Protein slows the release of glucose [aka sugar] into the bloodstream, preventing blood sugar spikes after consuming a meal or snack,” says Katie Vaughn, MS, RD. Something as simple as pairing a piece of fruit with a handful of nuts or nut butter, or having Greek yogurt topped with fresh fruit can make a big difference, notes Vaughn.
Originally published September 2019, updated with additional reporting
Make progress every day while you work on fitness and nutrition goals, like eating more protein. Go to “Plans” in the MyFitnessPal app for daily coaching and easy-to-follow tasks to keep you motivated.