Weight loss, burn fat, and exercise (exercise intensity and fat burning)

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People who want to lose weight, should increase their physical activity level. Regularly exercising makes weight loss easier. Also, when regularly exercising muscle mass will be better preserved, which makes losing and controlling your weight easier. A myth to lose weight through exercise, is that you should do a low intensity workout. In order to dispel this myth, the following issues will be discussed: energy intake and energy expenditure (energy balance), exercise intensity and burning fat and fitness. The myth of locally burning fat is also negated.

What is energy (energy balance)?
The energy balance consists of two components: the energy expenditure and energy intake. Both concepts are explained below.

Energy expenditure:

Energy expenditure is the amount of energy the body needs for all body processes to run smoothly and physical activity. Exercise (sports or other physical activity) is an important component of energy expenditure. The energy expenditure of men who are moderately physical active (daily 30 minutes of moderate intensity exercise) is 2500 Cal. The energy expenditure of women who are moderately physical active (daily 30 minutes of moderately intense exercise) is 2000 Cal.

Energy intake:

Energy intake consists of our total food and fluid intake. When energy intake exceeds energy expenditure the body weight (and body fat mass) will increase. During this period the energy balance is positive. When energy expenditure exceeds energy intake the body weight (and fat mass) will decrease. The energy balance is negative.
To gain 2 pounds of fat mass the energy intake  should exceed energy expenditure with approximately 7000-9000 Cal. To lose 2 pounds of fat mass energy expenditure should exceed energy intake with approximately 7000-9000 Cal. For example, when daily energy intake exceeds energy expenditure with only 60 Cal (energy of a small piece of chocolate), the fat mass will increase in 1 year with 5 to 6 pounds.

Exercise, physical activity, exercise intensity, and burning fat
Exercise increases energy expenditure. To exercise different energy sources are broken down, to release the energy from these sources. There are several energy sources, but the main energy sources are carbohydrates and fats. The exercise intensity affects both the energy expenditure and the relative contribution of these energy sources.

Rate of perceived exertion, heart rate and exercise intensity
Exercise intensity can be estimated with a heart rate monitor and / or a little less objectively by observing the rate and depth of breathing.

Exercise intensity estimating with a heart rate monitor:

The exercise intensity can be estimated fairly reliably with a heart rate monitor. This requires two things: the age and percentage of maximum heart. The maximum heart rate is easy to estimate by subtracting your age 220. For example: the age is 20 years, the maximum heart rate (220-20) = 200.
The percentage of the maximum heart where one wants to exercise, determines the exercise intensity:

  • 60-65% of maximum heart rate (0.65 × 200 = 130) is engaging in moderately intense exercise.
  • 80% of the maximum heart rate (0.8 × 200 = 160) is engaging in heavy intense exercise.
  • 90% of the maximum heart rate (180 in the above person) is very heavy intense exercise.

Exercise intensity estimated with breathing depth and breathing rate:

It is not strictly necessary to use a heart rate monitor the exercise intensity. By monitoring the rate and depth of breathing, exercise intensity can also be monitored.

  • For moderate intensity exercise the breathing will be a little faster and deeper, but it is still possible to talk in full sentences.
  • In a relatively intensive exercise breathing rate will be faster and breathing depth will be deeper, but it is possible to speak in words, but not in sentences.
  • For a very heavy exercise you will be panting and it is no longer possible to talk.

Exercise intensity and energy expenditure
As previously written, the energy expenditure should exceed energy intake in order to lose weight. At resting conditions, the energy expenditure is small. It should be clear that energy expenditure increases during exercise. Energy expenditure is increased by exercise. During exercise of high intensity, energy expenditure is larger than in exercise of lower intensity. During exercise of high intensity the demand for energy of the contracting muscles is high. In other words, in 30 minute run, the body expends more energy than during a 30 minute walk. Thus, when exercise intensity increases, the energy expenditure will also increase. In other words high intensity exercise increases energy expenditure more, than low, or moderate intense exercise. When the amount of time you can daily spend on exercise is limited, and the goal is to lose weight, exercise intensity should be high. For example, when you can exercise daily for 30 minutes, you better choose  running than walking. When you can exercise for hours, you can better exercise moderately intense, because high intense exercise can not be sustained for a long time.

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Exercise intensity and burning fat
During exercise (at rest also), the body burns fat and carbohydrates. When these nutrients are burned, they provide energy. The energy is used for the muscles to contract, and other bodily processes to maintain. Based on 3 situations, the relationship between energy expenditure, exercise intensity and fat burning explained.

  • Situation 1: energy expenditure and burning fat at rest:

While in rest the relative contribution of fat oxidation (about 80-90%) is the greatest, the total energy expenditure is small. The energy expenditure is small at rest and is around 0,5 Cal per pound of body weight per hour. That is approximately 90 Cal per hour for someone of 190 pounds. 80-90% of the 90 kcal is provided by fat oxidation. There will be about 8 grams of fat burned per hour.

  • Situation 2: energy expenditure and fat oxidation during moderate intense exercise (60-65% of maximum heart rate, eg walking at a speed of 3,5 MPH):

During moderate intense exercise total energy expenditure is larger than in resting conditions. The relative contribution of fat oxidation to total energy expenditure is approximately 50-60%. While walking with a speed of 3,5 MPH, the energy around expenditure will be approximately 3 Cal per pound of body weight per hour. That is 540 Cal per hour for someone of 190 pounds. 50-60% of the 540 kcal is provided by fat oxidation. There will be about 36 grams of fat burned per hour.

  • Situation 3: energy expenditure and fat oxidation during intense exercise (80% of maximum heart rate, eg running at a speed of 7 MPH):

During intense exercise total energy expenditure is larger than during moderate intense exercise. The relative contribution of fat oxidation to total energy expenditure is approximately 30-35%. While walking with a speed of 7 MPH, the energy around expenditure will be approximately 5,5 Cal per pound of body weight per hour. That is 945 Cal per hour for someone of 190 pounds. 30-35% of the 945 Cal is provided by fat oxidation. There will be about 36 grams of fat burned per hour.

From the above described situations it is evident that the relative contribution of fat oxidation in total energy expenditure, decreases when exercise intensity increases, but in absolute terms there is not much difference between the amount of fat that is burned during moderate and intense exercise. What is also clear, is that the energy expenditure is much higher in the latter situation. Therefore, the energy balance is more negative when intensely exercising. In situations where there is little time to exercise, you be can do intense exercise. Furthermore, the energy expenditure after heavy exercise will be higher for a longer period of time. The higher energy expenditure after heavy exertion is called EPOC (Excess Post Oxygen Consumption). However it is not wise to engage in very intense exercise after consulting your physician.

Exercise Intensity and physical fitness
There is a clear relationship between exercise intensity and the increase and maintenance of physical fitness. People who regularly train intensely will gain much faster gain a certain physical fitness level and better maintain their physical fitness. This is the case even if the exact same total training work is performed. In other words, someone is fitter when this person 3 times per week runs 10 miles instead of 3 times per week walks 6 miles. Exercise of a high intensity gives a greater stimulus to the muscles and the cardiovascular system, then exercise of moderate intensity. The result is that the body can release more energy (energy expenditure). The body is after a period of training, capable to run 8 MPH at 80% of maximum heart rate instead of running 6 MPH. The energy expenditure is greater when running 12 miles instead of running 6 miles. In other words, after a training period, the total energy expenditure of a training will be higher, even when training at the same exercise intensity as before a training period. Often heavy light exercise programs will be performed to build physical fitness. The principle of a heavy light program is that one day training is heavy and the next day training is light.

The myth of local fat burn

Often people do a lot of abdominal exercises (crunches, sit ups) to burn abdominal fat. This is nonsense. It is not possible to locally burn fat. Studies in tennis, for example, concludes that the arm that is dominant and therefore during training and matches often used, uses as much subcutaneous fat compared with the non-dominant arm.
The only way to lose fat and lose weight is through a negative energy balance. It appears that certain areas in the body where fat is stored, release fat easier than other places in the body. Fat from the abdominal area is easier broken down, than fat on the hips. Therefore it seems that men (often more abdominal fat) lose weight easier than women (often little more fat on the hips). The only way to lose fat locally, is to surgically remove fat (liposuction). This is expensive, and does solve the problem of a positive energy balance.

Exercise Duration and fat burning. How long does it take you to burn fat?
It is often said that fat burning starts after 20 to 30 minutes of exercise. This is not true. However, the first 20 to 60 minutes of a training fat stores of the muscle are burned, thereafter fat, from fat stores of the fat between the organs, and the subcutaneous fat is burned. After exercise, the fat stores in the muscles will be fueled from fat stores in the subcutaneous tissue and fat between the organs. Ultimately, the fat thus indeed from the subcutaneous adipose tissue and adipose tissue between the organs is burned. To lose weight the energy balance has to be negative. This can be done by either with 30 minutes continuous exercise, or with 3 x 10 minutes exercise.
It is indisputably clear that to lose weight people should have a negative energy balance. This can be achieved by becoming physical active or cut down in energy intake. This can be done by either with 30 minutes continuous exercise, or with 3 x 10 minutes exercise. It appears that when people exercise 3 x 10 minutes expend a bit little more energy, than when people 30 minutes continuously exercise. This is because people who exercise 3 x 10 minutes, tend to exercise intensive and therefore increasing energy expenditure .

General advice:

Especially for people who are untrained it is unwise to engage in very intense exercise without consulting your physician. Below are some general recommendations:

  • Visit a sports physician to control your cardiovascular health.
  • A sports physiotherapist can make a personalized training schedule.
  • Buy appropriate clothing and footwear.
  • Gradually increase your exercise intensity.
  • Guard against overload injuries to joints and muscles.

In summary
Weight gain and weight loss are, respectively, the result of a positive and negative energy balance. It is not possible to locally burn fat. By exercise,  and physical activity, energy expenditure increases and a result can be a negative energy balance. During exercise of moderate intensity, relatively more fat is burned than during exercise of high intensity. However the total amount of fat that is burned and the energy expenditure during and after exercise is greater at a high intensity exercise work out compared with exercise of moderate intensity. If the goal is weight loss, it is better regularly engage in an intensive workout. Also, the physical fitness level will increase faster with regular intense exercise, so eventually the energy expenditure during exercise further increase. However, it is unwise to daily engage in intense exercise. Also consult a physician and sports physiotherapist before engaging a intense exercise regime.

Finally
Structural lifestyle changes through healthy eating and sufficient exercise is the most effective way to lose weight permanently.