Fat Burning Zone
Is it true that you can burn more fat and calories by doing a certain type of exercise? The answer is yes and no! The reality is that it depends on a few key variables. When you exercise, you burn calories mainly coming from fat and carbohydrates. If you walk at a very slow pace you burn more fat calories per minute than carbohydrate calories, but fewer overall calories per minute than if you exercise at a harder level. As you begin to walk faster and move into a more moderately intense workout, your body will shift from burning a greater concentration of fat into burning a greater concentration of carbohydrates, and burn a greater number of overall calories per minute.
Carbohydrates, fat and protein are our three main energy sources from food that we use to exercise. These nutrients are found in different amounts in foods and are broken down by the body to provide energy. Fat is the richest food coming in at nine calories per gram. Alcohol is second in calorie count with seven calories per gram, followed by carbohydrates and proteins at four calories per gram. Now that you know how many calories are in each food and/or drink source, you can better appreciate how quickly one can gain weight by eating high fat food or drinking too much alcohol. One serving of food rich in fat such as ice cream is twice the calorie count as the same serving size of a protein rich food such as yogurt. However, one gram of fat releases twice as much energy as one gram of carbohydrate or protein — but this doesn't mean it's the best fuel for exercise! That depends on the type of exercise and how long you exercise.
The most ideal fuel for working your muscles is glucose, especially as your exercise intensity increases. Glucose is formed by the breakdown of carbohydrates (sugars and starches) in your diet and is stored as glycogen in the muscles and liver. Your body, however, can only store a limited amount of glycogen.
The amount of each fuel — carbohydrates, fat and protein — you use during exercise depends on various factors:
- Past eating habits
- Current fitness level
- Type of exercise
- Intensity of exercise
- Length of workout
- Frequency of workouts
Anaerobic exercise — defined as shorter duration, higher intensity exercise — uses mainly carbohydrates broken down into glucose, whereas aerobic exercise uses all three fuels, with protein used to a lesser extent than glucose and fat.
During low intensity exercise, which uses less than 300 calories per hour, you use a greater proportion of fat, a smaller proportion of glucose and fewer calories. As you increase your exercise intensity, your body will gradually use less fat, but more glucose and more calories. Therefore, most of the energy used during moderate and high intensity exercise will come from glucose.
If you continue to exercise aerobically for a longer period of time, your body will gradually use more fat and less glucose in an attempt to conserve your body's limited glucose stores. The fitter you are, the more efficiently your muscles use fat and the longer you can work out.
Your body does burn a higher percentage of calories from fat in the fat burning zone, or at lower intensities. But at higher intensities, you burn a greater number of overall calories which is what you should be concerned about if you're trying to lose weight. Remember, a calorie is a calorie, so your goal is not necessarily to worry about the type of calories you burn, but rather focusing on your goal of burning as many calories as possible.
The chart below explains total calories and fat calories expended by a 130 lb. woman during cardio exercise.
Remember your goal is to burn as many calories as possible to achieve your overall weight loss goal. Your workout programs should be a combination of longer duration, slower endurance workouts along with shorter, higher intensity workouts, which are a great way to burn more calories in a shorter period of time and build endurance.
Your Target Heart Rate and Personal Fat Burning Zone
To discover your ideal personal fat burning zone you need to calculate your Target Heart Rate Training Zone. The American College of Sports Medicine recommends healthy adults exercise within a range of 60-80 percent of their Heart Rate Reserve. Your optimal heart rate training zone may vary depending on your health and physical fitness status and any medications you are taking.
Now that you know the type of exercise that will give you the greatest calorie burn for your time spent you can have confidence in your exercise program. You now know that even if you can only fit in 20 minutes on a busy day, you can use that 20 minutes exercising at a moderate or higher intensity. For example, power walking on a break at work is better than a leisurely stroll to gain the greatest calorie burn in the short period of time you have available. By applying these simple exercise physiology principles and maximizing the math inside your body you will achieve the greatest benefit from your workouts!
Rate of Perceived Exertion (RPE)
If you are not interested in monitoring your heart rate during exercise to achieve your weight loss goals, another simple, medically-based tool you can use to monitor your exercise is Rate of Perceived Exertion, or RPE.
RPE is your own assessment, on a scale from 0 to 10, of how hard you perceive yourself to be working. This feeling should reflect how heavy and strenuous the exercise feels to you, combining all sensations and feelings of physical stress, effort and fatigue. Do not concern yourself with any one factor such as leg pain or shortness of breath, but try to focus on your total feeling of exertion.
Rating yourself using the Borg-RPE scale gives you a good idea of the intensity level of your activity. You can use this information to speed up or slow down your exercise to reach your desired range. Try to determine your feeling of exertion as honestly as possible without thinking about the actual physical load. Your own feeling of effort and exertion is important, not how it compares to others.
If you decide to use RPE instead of monitoring your heart rate during exercise to achieve your weight loss goals, you should strive to achieve an RPE of 5 to 6 on your higher intensity exercise days, and an RPE of 3 to 4 on your slower, longer duration exercise days. As always, be sure to monitor yourself carefully when you exercise so you stay within a safe intensity for your current fitness level, and remember to always stop exercising if you feel any strange sensations, shortness of breath, pain in your head, neck, arms, back or chest, lightheadedness, dizziness or any other unusual or strange sensations. Should you experience any of these sensations during exercise, stop exercising. If the symptoms don't stop or if they get worse, call 911. If the symptoms do improve when you stop exercising and you feel fine, you should still call your physician and schedule an appointment to review an appropriate exercise prescription with your physician.
Target Heart Rate Training Zone — The minimum and maximum heart rate that is most appropriate for you. You should exercise within this zone.
Percent Effort — A basis for determining your heart rate during exercise. The higher your percent effort, the harder you are exercising and the higher your heart rate.
Rate of Perceived Exertion — Your own assessment of how hard you perceive yourself to be working.
Resting Heart Rate — Your true resting heart rate is measured when you first wake up in the morning or after sitting for at least five minutes.
Recommended Percent Effort
40-50% Beginner Exerciser
50-60% Intermediate Exerciser
60-70% Advanced Intermediate Exerciser
70-85% Advanced Exerciser