Nine signs you're not getting enough protein, according to experts

A new health overview highlights nine signs that protein intake may be too low, even when daily calories meet or exceed needs. The assessment draws on guidance from physicians and registered dietitians who say protein is essential for building and repairing tissue, regulating metabolism, and supporting immune function. When intake falls short, the body may compensate by breaking down existing protein stores, which can affect energy, recovery, and overall function.

A clear early clue is persistent fatigue. Even with adequate sleep, people may feel consistently tired if their protein intake is too low because amino acids are needed to repair cells and regulate energy metabolism. The absence of steady amino acids can blunt energy production and leave you feeling foggy through the afternoon. Protein also helps stabilize blood sugar, which can blunt the midafternoon energy crash that follows carb-heavy meals. Health professionals note that fatigue, reduced energy, and slower workout recovery are common signals of insufficient protein.

Muscle loss or difficulty building muscle is another frequent sign. Muscle tissue relies on protein to repair and grow, so inadequate intake can leave you weaker, with less definition, or struggling to maintain gains despite regular exercise. When protein drops, the body may break down lean mass to harvest amino acids for vital processes, which can slow metabolism and complicate weight management. Clinicians note that if stair climbing feels harder or grip strength seems weaker, it may reflect insufficient protein rather than age alone.

You may notice persistent hunger or poor satiety. Protein is among the most satiating macronutrients, helping to signal fullness and regulate appetite. When meals rely more on carbohydrates and less on protein, blood sugar can spike and crash, driving cravings for more food. Experts advise aiming for about 15–30 grams of protein per meal to improve fullness and curb overeating over the day.

Hair, skin, and nails can offer early clues. These tissues are rich in keratin and collagen, both dependent on adequate amino acids. Fatigue, thinning hair, and brittle nails are commonly observed when protein is scarce, as the body prioritizes essential functions over cosmetic tissues. While not a diagnostic tool alone, these signs can point to a broader pattern of insufficient protein intake.

A higher rate of illness or slower wound healing can emerge with chronic protein shortfalls. Antibodies and many enzymes that fight infection and support repair rely on protein. Over time, insufficient intake may leave the body less prepared to fend off infections or rebound from injury, even if other aspects of health appear stable.

Concentration and mood can be affected when protein is lacking. The brain depends on amino acids to synthesize neurotransmitters such as dopamine and serotonin, which regulate focus, motivation, and mood. When protein intake dips, some people experience slower thinking, reduced patience, or lower motivation, even if sleep and stress management are otherwise in good shape.

Recovery after exercise may take longer when protein is insufficient. During workouts, small muscle tears require amino acids to repair and rebuild tissue. Inadequate protein can slow this repair process, making workouts feel harder and limiting progress, even for individuals who otherwise eat a healthy diet and get sufficient rest.

Fluid balance can also be disrupted in more pronounced cases, leading to swelling or edema in the face, hands, or legs. Protein helps maintain proper pressure in blood vessels, and when levels are too low, fluid can accumulate in tissues. Mild edema can appear alongside fatigue and weakness as an early warning sign.

If you’re losing weight but feel weaker or more fatigued, you may be shedding muscle rather than fat. When protein is scarce, the body may catabolize lean tissue to supply amino acids for critical processes, potentially slowing metabolism since muscle helps burn more calories at rest.

How much protein do you actually need? Experts generally agree that the average adult needs about 1 gram of protein per kilogram of body weight per day. If recovering from illness or surgery, needs may rise toward 1.2–1.5 grams per kilogram. Some nutrition researchers advocate a range of 1.2–2.0 grams per kilogram for lean mass, metabolic health, and satiety. For a 150-pound person, that translates to roughly 80–135 grams per day, distributed across meals. A practical starting point is 15–30 grams of protein per meal or snack about every three hours, which could look like eggs and Greek yogurt at breakfast, chicken or tofu at lunch, and salmon or lentils at dinner. For many healthy adults, underconsumption presents a greater risk than overconsumption, and increasing protein intake can support energy, immune health, and metabolic function without requiring extreme dietary changes.

Overall, the guidance suggests protein should be a regular feature at every meal, not just for athletes or those aiming for bodybuilder physiques. Higher-protein diets have been associated with better body composition, improved blood sugar control, and potential longevity benefits, according to nutrition experts. If you’re unsure about your protein needs, a registered dietitian can help tailor a plan that aligns with activity level, health status, and personal goals.