Potential downsides of high-protein diets include nutrient imbalances and strain on the kidneys for individuals with pre-existing conditions. Excessive protein intake can lead to insufficient consumption of other vital nutrients, such as fiber, vitamins, and minerals found in fruits, vegetables, and whole grains. Some individuals may experience digestive issues, such as constipation, from low fiber intake. Additionally, highly restrictive diets may negatively impact mental health by contributing to feelings of deprivation or obsession with food. Overall, a balanced approach to macronutrients is essential for sustainable health.