Health and fitness applications have significantly reshaped how people manage their physical well-being by offering features such as activity tracking, diet monitoring, sleep analysis, and virtual coaching. These apps also promote social interaction and community support to enhance user engagement. This review explores their effectiveness in encouraging healthy behaviors and improving health outcomes. It also considers the role of emerging technologies like AI, machine learning, and wearables. Key challenges include data privacy, user adherence, and accessibility issues. The review highlights the need for more advanced, inclusive, and user-friendly app designs for better health optimization.