SHED FAT
To burn fat, aerobic exercise must not be high intensity. When you exercise too hard or become breathless while exercising, the energy which feeds your movement is drawn from glycogen in your liver and muscles, not your fat stores.
You do not start to burn fat as soon as you begin your work out. Getting your body to burn fat instead of glycogen depends on complex hormonal responses (adrenal hormones and insulin) to trigger your fat cells to release triglycerides into the blood. The first 20 minutes of exercise the body burns sugar from the glycogen stores. The next 10 minutes it is a mixture of sugar and fats. Only after 30 minutes does the body burn proportionately more fat (50 percent from fat). The key about fat burning is to exercise not hard but long.
Studies in exercise physiology show that the minimal aerobic threshold to shed fat demands continuous movements of at least 30 minutes duration carried out at least 3 times a week. It has to be continuous and should you stop and restart workout after 20 minutes of exercise, the hormonal shift has reverted to burning sugar again. For beginners, you may find that your muscles may not sustain exercise for 30 minutes. It is okay as it may take several weeks to build up your muscular strength first.
SLOW DOWN. Many so-called instructors advocate a training heart rate of 60-70 percent of the maximal heart rate (220 minus your age). However, at that kind of rate the unfit majority will reach their anaerobic threshold, and the body will burn mostly protein and sugar. That is why you see so many overweight women in aerobic classes and overweight men jogging in the park, panting like mad.
In fact, the optimal intensity of exercise for fat burning is far lower at 50-60 percent of your maximal heart rate. A daily walk of at least 30 minutes will burn far more fat than killing yourself at the gym.
Body fat is interesting stuff. It is very caloric dense. This means that it needs a lot of oxygen to be metabolized – broken down – so that it can be put into the bloodstream and used as energy. If your workout is too intense, the body will not be supplied with enough oxygen and switch to other tissue for energy. In effect it will stop burning your stored fat and increase its burning of protein and glucose, for these tissues require less oxygen to burn. Exercise too vigorously, say running or sprinting, and your body never gets enough oxygen to burn fat efficiently. For, as the intensity of your exercise increases, the amount of oxygen available decreases. When this happens, your body has to look for more and more sugar and protein to maintain the effort.
