Every professional has their opinion about when is the best time to do cardio in order to burn the most fat.  There is first thing in the morning, on an empty stomach, later in the evening, or anytime.  In this article I will address this common question using scientific fact.

So you have started a weight loss program and you aren’t sure of when the best time is to do your cardio or aerobic training.  Let’s take a look first at some of the opinions out there and see if we can apply some variations to those opinions.

There are many people out there who believe that doing cardio training in the morning on an empty stomach is best to burn fat.  The belief is that your body has not taken in any food (calories) and that your body will have no choice but to break down stored fat for energy.  After all your body has been fasting while you were asleep.  The question I have is where then is your body getting its energy from in order to perform your chosen exercise?

So when your body is in need of energy it first looks for carbohydrates as a fuel source.  These carbohydrates are stored as glycogen and are very easy for the body to use as energy.  Unfortunately these energy sources burn quickly and will become depleted quickly.  Once your glycogen stores have been depleted your body turns to fat to burn for fuel.  This process is a slow process and isn’t easy for your body to complete.

Since fat contains the highest amount of calories your body doesn’t burn a lot of fat for fuel. It can get all of what it needs by breaking down a very small amount of stored fat for energy.  I recently addressed ‘5 Of The Most Frequently Asked Fitness Questions’ in a previous article.  In that I stated that some people consider a training range between 55-70% of your maximum heart rate is the ‘fat burning zone’.  However during this phase of training you are not burning many calories. You would have to have to stay in this zone for a long period of time in order to burn enough calories to lose body fat.

There are others who believe that doing cardio training later at night is the best time to burn fat.  This opinion uses the theory that you will burn any remaining calories that you haven’t burned throughout the day.  Science shows that the only way to lose fat is to make sure that you have a calorie deficiency at the end of your day.  So then is this the best time to do cardio training since you will have burned calories that will not be stored throughout the night?  This makes sense but there is a problem with this process as well.

Sleep is important because it gives your body the time it needs to recover from your day.  Everything resets itself when you are sleeping.  Whether you had a stressful day, an intense workout, or were studying all day you need sleep to recover.  The problem lies in that your body still needs calories during sleep in repair itself.  Yes, you burn calories when you are sleeping.  In fact you are always burning calories.

Others advise that it doesn’t matter when you are doing your cardio training as long as you are doing it between 55-85% of your maximum heart rate.  This theory relies on whether or not you are eating a healthy diet.  In order to explain what I mean here look at the below example.

Jon does his cardio training at three o’clock in the afternoon 5 days per week.  He doesn’t really watch his diet and consumes many of his meals from a restaurant due to his busy work schedule.  Jon eats approximately 4000 calories per day and eats his final meal about an hour before bed.  Jon has struggled to lose fat and his Doctor has advised him that he is in the high risk category.

In the above scenario Jon’s attempt to lose fat will be unsuccessful.  He could do his cardio training right before bed and he would never burn enough calories to be at a deficit before bed.  This is why your diet and training must go hand in hand.

In the end science tells us that the ONLY way to lose fat is to make sure that you are burning more calories than you are taking in.  If you are eating a bad diet full of processed foods full of empty calories then you will never reach your goal of weight loss no matter how hard you are working out.  The time of day that you are doing your cardio training will not matter.  So then if your diet is on target and you are eating balanced meals that are in line with your goals, when you do your cardio training will not matter.  It then becomes a matter of what time works best with your daily routine.