| Most people are aware that doing some form of | | | | maximum heart rate, and 80% VO2max is equivalent |
| exercise is beneficial, not only for losing unwanted | | | | to 88% maximum heart rate. Using the maximum |
| body fat, but also for improving overall health. | | | | heart rate example above, you can easily determine |
| However, many are unaware of certain factors that | | | | your optimum fat burning and aerobic fitness heart |
| can significantly increase the fat burning potential | | | | rate zone. |
| while performing exercise and during recovery (rest). | | | | - 175 maximum heart rate x 63% = 110 beats per |
| Four of the most important factors to consider are: | | | | minute |
| time interval from last meal, type of pre-exercise | | | | - 175 maximum heart rate x 75% = 131 beats per |
| meal, intensity of aerobic exercise and type of | | | | minute |
| exercise (aerobic versus resistance training). | | | | - 175 maximum heart rate x 88% = 154 beats per |
| Time Interval from Last Meal to Exercise | | | | minute |
| Performance | | | | In the above example, the optimum heart rate during |
| How long should someone wait before performing | | | | exercise for fat burning is 110 beats per minute, and |
| exercise in order to maximize the amount of fat | | | | to increase aerobic fitness the heart rate range is |
| burned during exercise and while resting? There are a | | | | 131-154 beats per minutes. However, since burning |
| number of studies that address this very question | | | | fat is best achieved at lower intensities and improved |
| and have shown that fat burning is greater when | | | | aerobic fitness is accomplished when exercising at |
| exercise is performed after an overnight fast or in | | | | higher intensities - how does one manage to |
| the morning before having breakfast. | | | | accomplish both? |
| One such study (1) looked at eleven overweight and | | | | One solution is interval aerobic training. This type of |
| untrained men over a 4-month course of doing | | | | aerobic exercise incorporates both low-intensity and |
| aerobic exercise performed after either an overnight | | | | high-intensity in one workout session. An example of |
| fast or 3-hours after consuming a standard meal. The | | | | this type of exercise: warm up for a few minutes at |
| authors noted that the amount of fat burned during | | | | a low intensity then increase your intensity to 63% |
| exercise was significantly higher following an | | | | of your maximum heart rate or in the above |
| overnight fast than after 3-hours post-meal. They | | | | example, 110 beats per minute. Exercise at this |
| also observed that fat burning was even higher | | | | intensity for 5-minutes then increase your intensity to |
| during the recovery (resting) phase in the fasting | | | | 75%-88% of your maximum heart rate for 1-minute |
| group. In conclusion, the amount of fat burned during | | | | (131-154 beats per minute in the above example). |
| exercise and while resting was more pronounced | | | | Next, slow your intensity returning to your 63% |
| when exercise was performed after an overnight | | | | maximum heart rate for another 5-minute session, |
| fast as opposed to 3-hours after eating a meal. | | | | repeat this 5 to 1, 5 to 1 minute interval until your |
| But, what if you cannot exercise first thing in the | | | | desired time of exercise is finished. At the end of the |
| morning due to time restraints, and working out later | | | | session, cool down for a few minutes at a lower |
| in the afternoon or evening is more practical - what | | | | intensity before stopping. |
| are your options? The timing of your last meal is still | | | | Bottom Line: If your goal is to burn fat, implement an |
| very important as to the amount of fat burned | | | | interval aerobic training program. Exercise at 63% of |
| during your exercise session. Researches (2) studied | | | | your maximum heart rate with periodic increases in |
| the effects of exercise on fat burning in eight | | | | intensity to between 75 to 88% of your maximum |
| overweight and obese women in two trials of | | | | heart rate. Of course, only exercise if you are a |
| exercise: one performed 1-hour after a meal and the | | | | physically able and have been cleared to do so by |
| other performed 3-hours after the consuming the | | | | your doctor. |
| same meal. The amount of fat burned was greater | | | | Type of Exercise (aerobic versus resistance training) |
| during exercise and during rest in the 3-hour | | | | Both aerobic and resistance training (weight-lifting) are |
| post-meal group. | | | | important forms of exercise that develop different |
| Bottom Line: If your goal is to lose body fat, then | | | | systems and require various forms of fuels to |
| the longer you wait after eating a meal the more fat | | | | sustain. As explained above, aerobic exercise |
| you will burn not only during exercise, but afterwards | | | | performed at lower intensities burns more fat during |
| while resting. | | | | the exercise, but when the intensity in increased |
| Pre-exercise Meal | | | | more sugar is utilized. Resistance training is a |
| What you eat prior to performing exercise is also | | | | high-intensity form of exercise and consequently |
| very important regarding the amount of fat burned | | | | requires the utilization of sugar rather than fat while |
| during exercise and afterwards during recovery. | | | | performing the exercise, but during post-exercise |
| Individuals who consume carbohydrates before | | | | recovery the amount of fat burned increases. So the |
| exercising, especially alone, in large amounts or high in | | | | question becomes how should one incorporate these |
| glycemic rating, inhibit their ability to burn body fat | | | | types of exercises? |
| during exercise and afterwards at rest. Eight healthy | | | | Is doing aerobic exercise combined with resistance |
| sedentary women were fed either a high-glycemic or | | | | training (weightlifting) performed in the same session |
| low-glycemic breakfast 3-hours before walking for | | | | (concurrent training) better than doing them |
| 60-minutes(3). Each of the meals had the same | | | | separately on alternating days? Studies show, that |
| amounts of carbohydrate, protein, fat and total | | | | doing resistance training alone is superior to aerobic |
| calories, but differed in glycemic index rating and total | | | | exercise in burning fat calories within two hours |
| fiber: the low-glycemic index meal was higher in fiber. | | | | post-exercise. This is known as excess post-exercise |
| The researches noted that the amount of fat burned | | | | oxygen consumption (EPOC) and represents the |
| during exercise was twice as much after the | | | | amount of oxygen utilized by the body to return to |
| low-glycemic meal than the high-glycemic meal both | | | | pre-exercise status - during this time period, body fat |
| consumed 3-hours before exercise. The amount of | | | | is broken down to supply the energy needed. |
| fat burned during post-exercise resting was also | | | | Researchers (7) also compared two exercise |
| higher in the low-glycemic index group. | | | | sessions: aerobic immediately (within 5-minutes) |
| The glycemic index rating reflects the speed at which | | | | followed by resistance training and then resistance |
| carbohydrates are digested and absorbed into the | | | | training immediately (within 5-minutes) followed by |
| bloodstream resulting in elevations in blood sugar and | | | | aerobic exercise. They concluded that doing aerobic |
| insulin. The higher the glycemic index rating the more | | | | immediately followed by resistance training was |
| rapid the absorption and subsequent blood sugar and | | | | comparable to doing resistance training alone |
| insulin elevations. Insulin, a hormone produced by the | | | | regarding EPOC. In other words, performing |
| pancreas gland, regulates sugar and fat utilization. | | | | resistance training alone (separate session) and doing |
| When elevated, fats release from fat cells is inhibited. | | | | aerobic immediately followed by resistance were |
| Some common high-glycemic foods consumed at | | | | comparably effective in burning body fat, with a |
| breakfast are cereals (corn, rice, wheat), instant | | | | slight edge to resistance training alone. Regarding |
| oatmeal, white flour baked goods (toast, bagels, | | | | overall performance as measured by the physiological |
| croissants, doughnuts), sweetened jams, and white | | | | intended effects of aerobic exercise and resistance |
| potatoes (hash browns). | | | | exercise, performing each type of exercise alone is |
| Bottom Line: If your goal is to burn body fat, then | | | | superior than combining them into the same session. |
| consume low-glycemic carbohydrates in combination | | | | In other words, maximum results are achieved from |
| with quality proteins and fats at least 3-hours prior to | | | | resistance training when performed separately and on |
| performing exercise. Do not consume sports drinks, | | | | alternating days, and the same is true of aerobic |
| sugary fruit juices or high-glycemic carbohydrates | | | | exercise. |
| before regular exercise - doing so will inhibit your fat | | | | Resistance training routines should be designed based |
| burning potential. | | | | on individual ability, medical and fitness status, and |
| Intensity of Exercise | | | | should be adjusted and/or changed every 6 to 8 |
| Generally, the amount of fat burned during exercise | | | | weeks reflecting progress. Incremental adjustments |
| is inversely proportional to the intensity level. In other | | | | to exercise type, sequence, frequency, intensity and |
| words, the higher the exercise intensity the less fat | | | | duration are critical in preventing muscle adaptation |
| is burned (while exercising) with sugar (glucose) | | | | and "burnout," and allows for continued overall |
| becoming the dominate fuel source. Of course, this is | | | | improvement. |
| a very simplistic interpretation - the actual intensity | | | | Bottom Line: Overall, the only real advantage of doing |
| level of exercise is relevant to your fitness status. | | | | concurrent exercise is time-efficiency. Otherwise, |
| The better shape you are in, the more efficiently | | | | doing aerobic and resistance training separately and |
| your muscles will burn fat during exercise and while at | | | | on alternating days is superior when considering fat |
| rest. | | | | burning (EPOC) potential and maximum exercise |
| Aerobic fitness is determined by an individual's ability | | | | performance. Periodic adjustments based on individual |
| (heart and lungs) to supply the tissues with oxygen | | | | progress are important to avoid muscle adaptation |
| during exercise, and is known as VO2max. The higher | | | | and to allow for continued metabolic and fitness |
| someone's VO2max, the greater his or her aerobic | | | | improvement. |
| fitness. The goal is to increase your ability to burn fat | | | | References Cited |
| during exercise while increasing overall aerobic fitness. | | | | |
| Research (4) has shown us that exercising at 40% | | | | 1. Crampes et al, Effects of a longitudinal training |
| VO2max is the optimal for burning fat during exercise | | | | program on responses to exercise in overweight |
| and greater aerobic capacity is achieved when | | | | men, Obesity Research (2003); 11(2):244-256 |
| exercising at 60-80% VO2max. How do you translate | | | | 2. Dumortier et al, Substrate oxidation during exercise: |
| VO2max in a more realistic or easy way to | | | | impact of time interval from last meal in obese |
| understand and use? Without fancy lab equipment or | | | | women, International Journal of Obesity (2005); |
| exercise testing, an easy way to determine your | | | | 29:966-974 |
| desired exercise intensity range is to calculate your | | | | 3. Stevenson et al, Fat oxidation during exercise and |
| maximum heart rate - all you need is your age and a | | | | satiety during recovery are increased following a |
| simple formula (5). | | | | low-glycemic index breakfast in sedentary women, |
| Maximum Heart Rate (HRmax) = 205.8 - (0.685 x | | | | Journal of Nutrition (2009); 139:890-897 |
| age) | | | | 4. Jeukendrop et al, Fat Metabolism during Exercise: A |
| - Example Age = 45 | | | | Review Part II: Regulation of Metabolism and the |
| - 205.8 - (0.685 x 45) | | | | effects of training, International Journal of Sports |
| - 205.8 - 30.83 = 175 | | | | Medicine (1998); 19:293-302 |
| - HRmax = 175 beats per minute | | | | 5. Inbar et al, Normal cardiopulmonary responses |
| Now that you know how to calculate your maximum | | | | during incremental exercise in 20-70 year old men, |
| heart rate, all you have to do is take a percentage | | | | Medicine & Science in Sports & Exercise (1994); |
| of that number based on your desired intensity level | | | | 26(5):538-546 |
| for maximizing your fat burning potential: 40% | | | | 6. Swain et al, Target HR for the development of CV |
| VO2max is equivalent to 63% of maximum heart | | | | fitness, Medicine & Science in Sports & Exercise |
| rate (6). To improve aerobic capacity and fitness, | | | | (1994); 26(1):112-116 |
| increasing to and 60% VO2max is equivalent to 75% | | | | 7. |