Firstly, multiple research studies show both the pros and cons of exercising on an empty stomach, and whether or not it makes a difference at all. The theory is that working out on an empty stomach will burn more body fat because you don’t have any food in your system to burn. This may be an option for you if your only goal is to tap into your fat stores, but think about this: if you are exercising on an empty stomach, are you going to have enough energy to have an intense workout? Long-term, permanent weight loss needs to be achieved with sustainable exercise and endurance, and cardio on an empty stomach will reduce your aerobic capacity, making you less able to exercise. As a compromise, eat a light snack an hour before, so you have the energy you need for cardio but will still burn up your fat stores.
When it comes to the time of day, many experts say you should do cardio early in the morning because eight hours of sleep means you’ve been fasting. This can allow you to have a clearer mind and more energy throughout the day, but doing cardio in the evening can actually have more benefits. You might work better at night, especially as you have nutrients from the food you’ve eaten in the day waiting there to be used. As long as the workout is effective, pick a time of day that works best for you.
Finally, it has been said for years that slow cardio exercise helps you burn more calories from body fat, but before you decide to go down this route, you must define what your goal is and what you want for the long term. How do you want your body to look? Both slow, less intense exercise and fast, high intensity workouts can help you lose weight, so look at the body difference of marathon runners and sprinters, and see which one appeals to you. Long duration cardio workouts are best if you want to look lean, rather than muscular, whereas high intensity and fast workouts are the choice for you if you are looking for a more muscular and defined frame. See what works best for you.