Stress can significantly impact one's health and fitness journey by triggering a release of cortisol, a hormone that can lead to weight gain, particularly around the abdomen. It may also cause fatigue, disrupt sleep, and decrease motivation to exercise, making it harder to stick to a fitness regimen. Chronic stress can result in unhealthy eating habits as individuals may turn to comfort foods high in sugar and fat. Overall, managing stress is crucial for maintaining optimal health and staying committed to fitness goals.