A common sign of inadequate protein intake is a feeling of persistent fatigue or low energy. Protein is crucial for various bodily functions, including building and repairing muscle tissues, producing enzymes, and supporting metabolic processes. When protein intake is insufficient, the body may struggle to maintain muscle mass, leading to weakness and a general lack of energy. Other signs might include hair loss, weakened immunity, and difficulty recovering from injuries. Ensuring adequate protein consumption is essential for sustaining energy levels and overall health.