Traditional diets that restrict calories often fail to work for many people. Traditional diets often lead to yo-yo dieting – an endless cycle of weight loss and gain. Intermittent fasting (IF) is a lifestyle rather than a diet. Unlike other diets, it doesn’t focus on what you’re eating, it focuses on when you should eat. The 16:8 fast involves an eating window of 8 hours followed by 16 hours of extended fasts of up to 48 or 36 hours.