How to tell if not enough protein? Recognizing the signs of deficiency

October 8, 2025 •

4 min read

Protein is the second most abundant compound in the body after water, playing a crucial role in repairing tissues, creating enzymes and hormones, and maintaining a strong immune system. When your body's intake of this vital macronutrient falls short, you need to know how to tell if not enough protein is being consumed to prevent a range of health issues from developing.

Quick Summary

Chronic low protein intake can lead to subtle but noticeable symptoms, including muscle loss, fatigue, frequent illness, brittle hair, and swelling. Recognizing these early warning signs is key to addressing the issue and supporting overall health.

Key Points

Fatigue and Weakness: Persistent tiredness and general weakness are common first signs of low protein, as the body struggles to maintain energy levels.
Brittle Hair and Nails: Hair is primarily made of keratin protein, so insufficient intake can lead to dry, brittle hair, thinning, and weak nails.
Muscle Loss: The body will break down its own muscle tissue to access amino acids if dietary protein is lacking, causing a decrease in muscle mass and strength.
Edema (Swelling): Severe deficiency can lead to fluid accumulation in tissues, especially in the feet and ankles, due to low levels of the blood protein albumin.
Weakened Immunity: Protein is essential for producing antibodies, so a deficiency can compromise the immune system and lead to more frequent illnesses.
Increased Appetite and Cravings: The body may signal constant hunger to compensate for a protein deficit, often leading to increased cravings for high-carb snacks.
Mood Swings and Brain Fog: Protein provides amino acids needed for mood-regulating neurotransmitters, so low intake can result in irritability and poor concentration.

Protein is a fundamental building block for every cell in your body, essential for structure, function, and repair. Unlike carbohydrates and fats, the body cannot store protein, making daily intake through diet critically important. While severe protein deficiency is rare in many developed countries, marginal insufficiency is more common and can manifest in various ways that signal your body needs more of this nutrient.

Common Physical Symptoms of Insufficient Protein

Edema (Swelling)

One of the most noticeable signs of severe protein deficiency, though less common, is edema, or swelling in the hands, feet, and ankles. This occurs because proteins like albumin help maintain fluid balance in the blood vessels. When protein levels drop, fluid leaks into surrounding tissues, causing puffiness. While other health issues can cause swelling, it is a classic symptom of extreme protein malnutrition, known as kwashiorkor.

Hair, Skin, and Nail Problems

Protein is the primary component of hair, skin, and nails, so a deficiency can lead to visible changes. Hair may become brittle, dry, and thin, with increased shedding, and nails can become weak and brittle with noticeable ridges. In severe cases, skin can become flaky and pale. Your body prioritizes more vital functions, so resources are diverted away from non-essential areas like hair, skin, and nails first.

Loss of Muscle Mass and Weakness

Muscles are the body's largest reservoir of protein. When dietary intake is insufficient, the body breaks down muscle tissue to supply essential amino acids for more crucial functions. This can result in a loss of muscle mass over time, leading to overall weakness and a decline in physical strength. Older adults are particularly susceptible to this, a condition known as sarcopenia.

Impact on Mood, Energy, and Immune Function

Constant Fatigue and Low Energy

If you find yourself feeling unusually tired or sluggish, it could be a sign you're not getting enough protein. Protein is a vital energy source, and a deficiency can lead to a drop in overall energy levels. Moreover, protein is needed to produce hemoglobin, which carries oxygen in the blood, and low levels can contribute to fatigue.

Increased Hunger and Cravings

Protein promotes feelings of fullness by influencing appetite-regulating hormones. When your diet lacks sufficient protein, you may experience constant hunger and cravings, especially for sugary or carbohydrate-heavy foods. This can lead to increased calorie intake and potential weight gain as the body signals for more nutrients to compensate.

Weakened Immune System

A strong immune system depends on protein to create antibodies and other immune components. A deficit can impair the body's ability to fight off infections, leading to more frequent illnesses and a longer recovery time. This is why people with chronic protein deficiency often find themselves getting sick more often.

Mood Swings and Brain Fog

Amino acids, the building blocks of protein, are essential for producing neurotransmitters like serotonin and norepinephrine, which regulate mood and cognition. Low protein intake can affect these brain chemicals, potentially contributing to mood swings, irritability, and difficulty concentrating.

How to Increase Your Protein Intake

If you suspect you are not getting enough protein, increasing your intake can help reverse these symptoms. A balanced approach includes incorporating high-protein foods into each meal and snack. To ensure a complete amino acid profile, especially for plant-based eaters, combine various protein sources throughout the day.

Best High-Protein Food Sources

Lean Meats and Poultry: Chicken breast, lean beef, and turkey.
Fish and Seafood: Salmon, tuna, and canned fish are excellent sources.
Eggs: A convenient and complete protein source.
Dairy: Greek yogurt, cottage cheese, and milk are high in protein.
Legumes and Beans: Lentils, chickpeas, and black beans.
Nuts and Seeds: Almonds, peanut butter, and edamame.
Whole Grains: Quinoa and amaranth offer more protein than refined grains.
Soy Products: Tofu and tempeh.

Recommended Protein Intake Based on Lifestyle


Lifestyle/Group	Recommended Daily Intake (per kg of body weight)	Notes
Sedentary Adult	0.8 g	The minimum required to prevent deficiency.
Endurance Athlete	1.2 to 1.4 g	To support recovery and muscle repair from intense exercise.
Strength-Training Athlete	1.2 to 1.7 g	Necessary for building and repairing muscle mass.
Older Adult (>65)	1.2 to 1.6 g	Higher needs to combat age-related muscle loss (sarcopenia).
Pregnant/Breastfeeding	1.1 to 1.3 g	To support fetal growth and milk production.

It is important to remember that these are general guidelines, and individual needs can vary. It is always best to consult with a healthcare professional or registered dietitian for personalized advice.

Conclusion

While a severe, life-threatening protein deficiency is rare for most people, paying attention to subtle signs can be beneficial for overall health and wellness. Symptoms like persistent fatigue, increased hunger, brittle hair, and a weakened immune system can all point towards inadequate protein intake. By understanding these signals and incorporating more high-quality protein sources into your daily diet, you can address the issue and support your body's optimal function. To learn more about protein requirements for specific lifestyles, see the guidance from the American Heart Association.

Frequently Asked Questions

You can quickly boost your protein by having a protein shake, snacking on Greek yogurt or cottage cheese, or adding a scoop of protein powder to a smoothie.

Yes, protein deficiency is directly linked to hair loss and thinning. Hair is primarily made of protein, and a lack of it can weaken the hair shaft and cause increased shedding.

Older adults, athletes, pregnant or breastfeeding women, and individuals recovering from illness or surgery are at higher risk due to increased protein needs.

If your fatigue is accompanied by other symptoms like muscle weakness, increased hunger, or brittle hair, it could be a sign of low protein. Protein is a key energy source, and a lack of it can leave you feeling drained.

Great high-protein snack options include Greek yogurt, cottage cheese, hard-boiled eggs, a handful of almonds or other nuts, and edamame.

In severe cases, a lack of protein can cause edema (swelling) in the legs, feet, and ankles because blood proteins like albumin are too low to maintain fluid balance.

Animal proteins and a few plant sources like soy and quinoa are 'complete' proteins, containing all essential amino acids. Most plant proteins are 'incomplete,' but consuming a variety throughout the day, such as rice and beans, ensures you get a full amino acid profile.