PT on the Net Research

Calorie Burn in the Morning


Is it true that people burn more "fat calories" when they exercise first thing in the morning before eating anything? Or does the energy they use come from muscles rather than fat reserves? Please explain.


This area of metabolic demands is difficult to answer directly. The reason for the difficulty is you do not state what type of training is being completed. I hate to assume, but if your client is like most of us, then it is just plain old “fat cals.”

As you no doubt know, energy expenditure is calorie expenditure. The question is what percentage of the calories are fat, carbs or in some cases proteins. When someone is trying to drop “pounds,” then a negative calorie diet usually accompanies an exercise program. The bottom line for the scale is “calories in vs. calories out.” Most people do not care where the calories are coming from, as long as the scale moves down.

If someone is trying to drop “fat” only and is trying to hang onto muscle for some type of athletic event (i.e., making weight), then they will be concerned with where those calories are coming from. Many times, someone trying to “make weight” is training a lot on top of calorie concerns. Hydration, glycogen restoration and nutrient intake become a concern. So, one way, and there are many, is doing some aerobic work in the morning.

Morning aerobic training can be achieved several ways. If a person is training twice a day, then carbohydrate metabolism and balanced blood glucose levels are priority. This means that when someone wakes up, they drink plenty of fresh water. When the aerobic work begins, then they will sip on a little carb plus protein mix (maybe 20 grams plus 10 grams). This helps keep lean tissues. There is an axiom in exercise physiology that says, “Fat burns in carbohydrate flame.” And with some of the latest research, we can add a small amount of amino acids into that flame. Waiting until exercise begins to drink the mix will decrease the amount of insulin released and therefore maintain fat oxidation and preserve lean tissues.

The training intensity that someone could use to maximize the fat burning seems to fall around 50 to 60 percent of VO2 max. This correlates to about 65 to 75 percent max heart rate. Anything higher than that relies on glycogen stores and anything lower may not use the same amount of total calories. I am unsure of the fitness level of your client. Your experience is the key there.

Fat metabolism is a complex area and one that is heavily researched. If your client is only concerned with dropping fat and not big glycogen restoration, they might want to just drink water after rising, plus a cup of coffee. Caffeine has been shown to increase fatty acid use during exercise. Caffeine does many things and hypertension can be one of them, so make sure your client can function on caffeine before you turn them loose. A 65 percent max heart rate for 20 to 30 minutes, three to four days a week should do it. Have your client drink plenty of water before, during and after the workout. This will ensure the caffeine did not cause a dehydration effect.

These are just a few choices for you and your client. The morning is good due to the suppression of insulin levels from an all night fast. Most people have enough fuel in their liver and muscle to support the blood glucose. However, you never know how someone will react to a given workload. As always, check with the person’s health care provider if you have any concerns.

Good luck!