Common causes of fitness plateaus include lack of variety in workout routines, insufficient recovery, and inadequate progression in intensity or volume. When the body becomes accustomed to a specific regimen, it stops adapting, leading to stagnant performance. Nutritional factors can also contribute, as insufficient caloric or protein intake may hinder recovery and growth. To overcome plateaus, it's essential to incorporate new exercises, adjust workout frequency, or modify diet. Additionally, ensuring proper rest and recovery allows the body to adapt and continue progressing toward fitness goals.