The Myth of the Fat-Burning Zone

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Caloric Expenditure

Fat loss is all about caloric expenditure. You must burn off more calories than you consume to lose body fat. Even among the proliferation of diets—low carb, low fat, high protein—this simple rule remains.

The key to achieving this is not aerobic training, which will burn calories only while you are doing it. It is anaerobic training, which burns calories while you are working out and increases the calories burned for hours afterwards. In the case of weight training, building muscle burns calories, as long as that muscle is retained—even during sleep.

During anaerobic exercise, the body burns a lot of calories. However, the metabolism still remains elevated following a workout. At one time, this was referred to as oxygen debt, but is now known as excess post-exercise oxygen consumption (EPOC). Recovery of the metabolic rate back to pre-exercise levels can require several minutes for light exercise (aerobic training), several hours for very heavy exercise (anaerobic cardio training), and even up to 12 hours or longer for prolonged, exhaustive exercise (interval training or circuit weight training).

The EPOC can add up to a substantial energy expenditure when totaled over the entire period of recovery. If oxygen consumption following exercise remains elevated by an average of only 50 milliliters per minute, and the metabolism remains elevated for five hours, this would amount to an additional expenditure of 75 kilocalories over that time period.

This major source of energy expenditure—which occurs during recovery but is the direct result of exercise—is frequently ignored in most calculations of the energy cost of various activities. Doing the math, if the individual in this example exercised five days a week, he or she would lose the equivalent of approximately 0.1 pounds of fat in one week just from the additional caloric expenditure during the recovery period alone.

Is the effect accumulative? If you trained the next day while your metabolism is still elevated will we have an even higher return? Science has yet to give an answer. However, I have seen amazing results with my clients using this exact protocol.

Interval Training

So, is there a better way of performing cardio workouts to prevent these adaptations and rapidly improve fat loss results? Yes. This is done through interval training.

Interval training refers to a series of intense activity separated by short rest periods. Utilizing interval training will eventually enable you to exercise at a higher overall intensity without getting as tired. This occurs because you alternate periods of high intensity exercise with periods of lower intensity, allowing you to do more work in the same time period than you could before.

The benefits of interval training lie in the fact that as you improve, the work intervals can be made increasingly harder, recovery intervals can be shortened or training can be performed at a higher speed. Like weight training, there is no limit to improvement.

Putting it All Together

In conclusion, endurance athletes to shed a few pounds should substitute the long, slow, steady-state training that is making them more efficient at storing fat with some high-intensity intervals. I recommend starting with five sets of one minute at increased intensity followed by two minutes of recovery. During the one-minute interval, push your limit. In your recovery, take it down to a level where you can carry on a conversation. This workout takes less than 20 minutes and will have your metabolism stoked for burning fat during the rest of the day.

Also include weight training in your schedule to build muscle and keep your metabolism up. Perform a full-body workout twice a week. This should take less than an hour to do and will get your metabolism cranking.

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Rachel Cosgrove owns a fitness facility in Santa Clarita, California, called Results Fitness. She and her husband wrote a book on their fat loss philosophies called Afterburn, based on the above concepts. Learn more about her at