The short answer is “for the rest of your life.” Implementing a diet for a short period of time, with the primary goal of losing weight, misses the point and won’t help you in the long run. For sustained weight loss and optimal health, it’s critical to adopt a dietary framework that you can sustain for the rest of your life. There is nothing wrong with adapting that framework over time based on your health and fitness goals. But if you don’t find a way of eating that you can maintain in the long run, you’ll likely regain any weight you lost while on a short-term diet.