You have probably heard all sorts of things in regards to the best time to do cardio. You have probably heard some people say that the best time to do cardio is first thing in the morning before you eat because it burns fat the best. You have probably also heard that after you consume carbs is good as well. So which one is right?
A lot of it depends on you. For me, performing cardio in the morning before eating, is not ideal. I feel sick and lethargic as I’m running and have lackluster workouts, but you may feel differently. Find a time of the day, whether it is before work, early in the morning, late at night, etc, where you feel the most energetic. Perform cardio at this time in the day.
There have been many studies saying that the best time to do cardio is early morning to increased fat loss. Listed below are three of these such studies, but make sure to take these studies with a grain of salt for reasons I will discuss later in the article.
A study conducted by the University of Kansas in 1985 showed that the optimal time to perform cardio was very early in the morning, which resulted in a greater fat loss than cardio performed later in the day.(1)
Another study conducted in Belgium showed the possible benefits of performing cardio early in the morning. The study consisted of 3 groups. One of the groups did no exercise, one of the groups did intense running and cycling early in the morning, and the final group did intense running and cycling later in the day. All three of the groups were put on an increased calorie diet that was high in fat. As expected, the group that performed no exercise gained weight. The group that performed intense exercise later in the day also gained some weight, although it was less than the first group. The group that performed intense exercise first thing in the morning, however, did not increase in weight further showing that cardio early in the morning may be a good time to do cardio.
In another study published in Medicine and Science in Sports and Exercise conducted at Kansas State University, showed that performing cardio in the morning may lead to increase fat burning. The researched measured caloric expenditure, carbohydrate and fatty acid metabolism, and respiratory gas exchange, and found that 67% of the total energy burned during aerobic exercise after a 12 hour fast was fat. This is a lot higher than the 50% fat expenditure achieved with the same exercise after eating or later in the day. This study explained that performing cardio exercise later in the day is not optimal.
Despite these findings, I only recommend performing cardio on an empty stomach if you feel comfortable doing so. If you think the best time to do cardio is first thing in the morning and you feel great doing it, then I would go for it. However, if you are anything like me, you will feel nauseous, sick, and light headed after a morning run and you won’t be able to exercise for nearly as long. If you do not have sufficient energy supplies during your exercise, your ability to maintain your exercise for long periods of time is unlikely and possibly dangerous. Food is the fuel for your workout and without that fuel there is only so long your body can run on empty.
Bottom line, however, is that the best time to do cardio is whenever you can get it done!! It doesn’t matter if it is in the morning, evening, afternoon, lunch break, after the sunset, under the stars, at midnight, etc.. The most important thing is to develop a routine that consists of regularly doing cardio.
Wilcox, Harford & Wedel. Medicine and Science in Sports & Exercise, (1985) 17:2.