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Exercise and fat metabolism

Exercise Health

Written by:
Birgitte Nymann ( www.nymanns.dk )
Author, speaker and educator within Exercise, health, nutrition and motivation. Concept – and seminar developer at Pro Academy, Denmark. Educated and trained in sport from University of Copenhagen.

For many years, we have been told that a walk is more fat metabolising than a run. Exercise at low intensity when you want to lose weight. Exercise for a long time, then you metabolise etc. etc.

It is correct that if you go for a walk, your metabolism is good as a percentage of your total energy consumption. If you run, your metabolism declines as a percentage of your total energy consumption, but you consume much more energy all in all. You stress your circulation much more and your metabolism increases significantly after a run compared to a walk.

A walk can easily be sufficient in the beginning, not everyone must take a run , but is important to keep the right intensity in order to achieve most possible improvements.

Fat metabolism

The human condition is measured in oxygen uptake per minute. As an example, most Tour de france bike riders have an oxygen uptake of over 7 litres per minut, where a normal active person has an oxygen uptake of approx. 4 litres per minute. If you are in a bad shape, your oxygen uptake can be down to approx. 2 litres per minute. In order to find out how much fat you metabolise at a given activity, you must know your oxygen uptake. Oxygen uptake is measured in a lab, so you cannot use the example mentioned below to measure your own metabolism. But be attentive for the sake of the example.

Exercise relatively hard when you want to lose weight

Your fat metabolism is high in percentage of your energy consumption, when you are resting and until you work at an intensity of approx. 65% of your maximum performance. When you work at 65% of the maximum performance, you consume more energy than when you sit on your couch . This means that your total amount of energy, and thus your total amount of metabolised fat is higher when you are moving.

If you start to exercise with an intesity higher than 60-65%, your fat metabolism declines and the carbohydrate metabolism increases. For this reason, it is popular to say that you should exercise easily to fat metabolise, but if you calculate the actual numbers for how much you actually metabolise, the score looks slightly different and there is actually no difference of how much fat you metabolise by working easily compared to working hard. The differens lies in the numer of calories that are metabolised. When you exercise hard, you metabolise more calories per minute than when you exercise easily, and this is what it is all about when you want to lose weight or just consume a lot of calories, so you prevent overweight and can allow yourself to eat a bit more.

Besides, the after metabolism is far more high when you have exercised hard, simply because you have ”toiled” your body more and the body has now a greater ”repair work” to do. When you are resting, the fat metabolism in percent is high, depending on what you have eaten and how good shape you are in. When you consume energy at rest, you also consume more fat. Therefore, the total amount of energy you use by exercising hard and the amount of fat, is actually significantly greater, even though it does not seem that at first sight.

Additional to the extra amount of energy you consume, comes all the improvements you get from exercising: better circulation, stronger heart, less stress, greater endurance, better posture and so on. These improvements are fewer and less effective by exercising easily

Exercise at high intensity can give low blood sugar = increased appetite

Bearing the above mentioned in mind, we should suggest that you always exercise at highest intensity possible. However, we suggest that you put most of your exercise at 65-80% until you are in a good shape. If you exercise at higher intensities, when you are not in the shape for it, it can result in low blood sugar, especially when you also have changed your diet to lose weight. When you eat less than you used to, it can result in a dive of your blood sugar at repeated intervals with a high intensity, because the body is not used to the changes of your diet or the changes in your exercise. This can mean that you have to stop too early and not consume that much energy on the exercise, or that you are very hungry after the exercise, and feel like eating a lot of food or sweets. If your exercise is primarily at 65-80%, you achieve all the advantages that there are – you metabolise many calories and you can keep going for relatively long. When you have exercised regularly for a longer period of time (more than 3 months), you can easily exercise at higher intensities without blood sugar problems as long as you have eaten sensibly before the exercise.

Interval training is the best and fastest way of improving your shapeI

As mentioned earlier, you can only exercise a short while at the highest intensities. The high intensities are used at interval training. Interval training is the best and fastest way of increasing your condition. Interval training means that you exercise for maybe 30 seconds and take 1 minute break, and then work again for 30 seconds and take a break again. The intervals can be varied endlessly. The advantage of interval training is that by making 5-10 intervals you train your condition (oxygen uptake) at the highest level and stress your muscles a lot. If you add up the time of every interval, you exercise quite long at a high intensity. Much longer than you could stress the body if you should exercise at the same high intensity by constant work. Interval training is also good when you want your body to get used to running. As an example, you walk 5-10 minutes as a warm-up and then you run for 1-2 minutes and walk for 1-2 minutes etc. In this way, you can keep running for more minutes than if you run constantly.

12 minute test

A test on a bike or running machine, where you keep the same intensity for 12 minutes. Check your pulse rate every minute and write it down or use a heart rate monitor with the possibility to get a print of the heart rate graph (is available to for example Polar heart rate monitors). Draw a graph and compare it with a new test every month. At the same intensity, the heart rate should be lower after a period of regular goal-oriented exercise.

If you perform the test on a running machine, use the same speed every time. If you make a walking test on the running machine, adjust it to 1-2 degrees up.

If you perform the test on a bike, make sure to ride with the same number of revolutions per minute to keep the same intensity (watt). Ride with about 50-60 revolutions per minute.

Ask the test person about how hard it feels, and compare their feeling at the same time when the next test is performed.

What to remember before you test:

  • eat no later than 2 hours before the test is performed
  • avoid to smoke for minimum 2 hours before the test is performed
  • avoid to drink coffee at least 2 hours before the test is performed
  • You should not exercise on the same day as the test is performed
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