Chapter 10: Exercise to Improve Body Composition

The endocrine/hormonal response to exercise is vitally important. What is the hormonal response to high-power activities?

- Increased levels of testosterone. - Insulin-like growth factor. - Human growth hormone.

There are two methods to calculate / estimate how much energy is expended by humans during exercise. They can be used to determine the amount of energy used or heat produced during an activity. What are they?

1. Direct Calorimetry: the direct measurement of heat production (uses suits to small chambers or large rooms). Is very accurate, but impractical. 2. Indirect Calorimetry: obstains an indirect esimate of energy production by measuring oxygen comsuption which can be converted to a corresponding value for energy production.

You cannot decrease the number of fat cells once you have them, but you can decrease the size of fat cells. What are three critical periods when the number of fat cells increases significantly?

1. During the last trimester of pregnancy. 2. During the first year of infancy. 3. During the adolescent growth spurt.

What two ways can the body increase its quantity of stored fat?

1. Fat cell hypertrophy: enlarging or filling exsiting fat cells with more fat. 2. Fat cell hyperplasia: increasing the total number of fat cells.

How many excess kcals need to be consumed for one pound of human adipose tissue to be stored in the body?

3500 kcal of excess energy.

What is insulin?

A hormone that regulates carbohydrate and fat metabolism. When you secrete insulin it signals cells in the liver, muscle and adipose tissue to take up sugar from the blood. In the liver and muscle glucose it is stored as glycogen and in adipose tissue it is converted to fat.

What is the glycemic index (GI)?

A measure of the effects of food on blood sugar levels. Carbohydrates with a high GI rating can be digested quickly causing a rapid rise in blood sugar levels. Carbohydrates that break down more slowly, releasing glucose more gradually into the bloodstream, have a low GI. Often this rapid rise in blood sugar results in a rise in insulin levels.

Olympic lifts and maximal sprints use an incredibly high number of muscle fibers in the explosive effort to produce high accelerations. What does this elicit? What else elicits this response?

A profound hormonal response. Squats and deadlifts stimulate a positive hormonal response due to the sheer weight being lifted which taxes the body.

If you have an hour to exercise and your goal is fat loss, should you do a slow and steady, moderate exercise, or an shorter, more intense exercise? Why?

A shorter, more intense exercise. The greater your energy requirements become, the more your body will switch to glucose and glycogen use, because of its efficiency. This is why when someone is working at a lower intensity they burn a greater percentage of fat than at the higher intensity. This is where the misconception that slow and steady cardio burns more fat. But, you will utilize more oxygen and burn more calories with shorter intense workouts.

What composes a health body composition?

Adequate musculature in all regions of the body, good bone and connective tissue density, and health body fat levels.

Why is it important to prevent over-fatness during childhood?

Because you cannot decrease the number of fat cells once you gain them, only the size of fat cells. You may not be able to alter your "genetic target" of fat cells during adulthood, but you can alter bad habits. New research shows that you may be able to alter the number of fat cells before adulthood, but there is no clear data yet. The number of fat cells seem to become stable sometime before adulthood, and any weight gain or loss thereafter is usually related to a change in the size of individual cells.

Would you burn more fat doing bike intervals, or stead-state cycling, even if you burnt the same number of calories? What does this tell us?

Bike intervals. It tells us that high power outputs elicit different (better) hormonal responses than low-power steady-state ones.

How would you write the net energy exchange that expresses the process of metabolism?

Calorie balance = kilocalories from food - (kilocalories of resting metabolism + kilocalories of physical activity + kilocalories used to digest food + kilocalories lost in excreta).

What is the energy balance equation (EBE)? What does it promote?

Change in energy stores = Energy intake - Energy expenditure. This is used to promote low-fat diets, since a gram of fat is 9 calories, and a gram of carbs and protein are 4 calories. However, evidence shows that low-fat diets do not work for most individuals.

Is it better to work on increasing speed or distance of your runs?

Distance, because the caloric expenditure is approximately the same whether the speed is fast or slow. But interval sprint work or high-paced running will elicit hormonal responses and increased core temperatures, which will result in your burning additional energy for a much longer time after exercise, compared to low-intensity work.

Do high-fat diets contribute to obesity?

Eating fat does not make you fat. Unless, of course, you are eating excessive amounts of calories from fat.

What is lipolysis?

Fat breakdown.

What types of foods cause a rapid rise in blood sugar and often a similar fast rise in blood insulin levels? How does this make us have excess body fat?

High-glycemic foods. Insulin is an essential hormone, but if levels are chronically elevated, you will tend to store more body fat and your cells may become desensitized to insulin, eventually leading to type 2 diabetes.

What does intense work do to your cells and metabolism?

It causes cellular damage. Exercise is a stressor at the cellular level, it is a debilitating process that forces the body to rebuild tissue and strengthen, and there are important hormones involved in this rebuilding process. Your metabolism stays elevated for much longer after a high power activity due to the action of adrenal gland hormones (epinephrine and norepinephrine) as compared with a low power workout.

Do you necessarily store energy just because you eat more? It is poor eating habits that cause a hormonal response, which then forces the body to store excess calories as fat. What is poor food intake?

It is not simply too many calories; it is high-carbohydrate calories, particularly simple sugars and refined flours, as well as total carbohydrate intake.

Studies show that many obese people do not eat a high volume of food compared to their thinner counterparts. Instead.... .... which contributes to their obesity.

It is often poor choices of foods, usually consisting of large amounts of sugar, refined carbohydrates, and other high-glycemic foods that cause a rapid rise in blood glucose which contributes to their obesity.

Does muscle tissue or adipose tissue expend more energy per day? How much more?

Muscle tissue. It burns 10 kilocalories per kilogram per day, compared to 2 kilocalories per pound of adipose tissue per day. This is a result of protein turnover.

Does the logic "a calorie is a calorie", and "a calorie burned is a calorie burned" hold true?

No.

If you managed to develop a negative energy balance of 500 kcal per day, how many pounds of adipose tissue would you lose in one week?

One. Also, remember that it is not simply about reducing calories, as it is the quality and quantity of food as well as the quality and quantity of exercise that will decide whether you achieve a negative energy balance.

During high-intensity exercise, you burn a lot of muscle and liver glycogen. When you eat carbohydrates, your glycogen stores are replaced, and if you haven't deleted your glycogen stores, any digested carbs (glucose) that exceed your immediate energy needs will be stored as fat. So should we eat low carbohydrate diets?

People who exercise regularly should not eat low-carbohydrate diets, as fat in the diet cannot be used to replenish glycogen stores. Therefore if you eat a high-fat, low-carb diet, you may not fully replace muscle and liver glycogen, and your ability to exercise will be diminished. Likewise, you do not need a high-carb diet, a moderate amount is enough.

Does vigorous exercise of moderate duration increase appetite and food intake?

Research shows that it does not. Physical activity is necessary for the normal functioning of the brain's feeding control mechanisms. A fine balance between energy expenditure and food intake is frequently not maintained in sedentary people. For them, daily caloric intake generally exceeds energy requirement.

What type of work will normalize gene expression and hormonal balance?

Resistance work and high-intensity work.

What is your basal metabolic rate (BMR)?

The base level of your daily energy expenditure; strictly speaking it is the amount of energy expended while at rest in a neutrally temperate environment after a 12-hour fast.

What is the set-point theory?

The body has an internal control mechanism, a set point, probably controlled by the hypothalamus in the brain, which drives it to maintain a particular levels of body fat. When you manage to reduce your body fat below your natural set point your body attempts to resist this change and conserve body fat by lowering your basal metabolic rate (BMR). When very low-calorie diets (fewer than 800 kilocalories/day) are used BMR may be decreased by as much as 45%. This greatly conserves energy and causes the diet to become much less effective. Some studies suggests that many people who have lost weight after crash dieting will remain at their new weight only if they consume about 25% fewer calories than those people who are normally at that weight and level of body fat.

Why do some people stay overweight, even if they are exercising and eating the same amount of calories as a lean individual?

The food we eat elicits a hormonal response, which determines how energy is stored in the body - that is, in the form of body fat. Basically, energy intake is not independent of energy expenditure, and the type of calories you eat does affect your energy output. For example, sugar, high-fructose corn syrup, and easily digestible carbohydrates drive an insulin response, and insulin drives fat storage. Many excellent researchers in this field argue that dietary fat - or even calorie quantity - is not the main culprit at all.

Research shows that repeated bouts of exercise cause enhanced fat metabolism compared with a single bout of prolonged exercise of equivalent total exercise duration. What would an example of this be?

Two 30-minute workouts on a cycling machine, with a 20-minute rest in between.

Why is walking better than running for heavy individuals?

When running, the landing impact results in a force approximately equal to three times your body weight being transmitted through your feet and legs. But walking has no airborne phase that must be controlled, therefore the forces are much lower (approx only 1.2 times body weight.)

Are the calorie-expending effects of exercise cumulative?

Yes! You don't have to run 50 kilometers all at once to burn one pound. You could run 10 kilometers for 5 days to burn one pound. Of course, other factors like hormones, metabolic rate and diet play a role.

Do low-fat diets drive hormonal triggers for fat accumulation?

Yes.

What is a metabolic benefit to higher-intensity workouts?

You work at much higher metabolic rates, and your metabolism stays higher for longer after the workout. Intense exercise (such as weight training, high-intensity interval training, plyometrics, sprints, and so on) can increase metabolic rate for hours (3 - 14 hours, depending on intensity) after a vigorous workout. Slow aerobic exercise doesn't raise metabolism very much and hence has little effect on metabolism after your workout; you can be back at resting metabolism within the hour after a slow, steady jog.

Spot reduction involves localized exercise in the belief that the muscles utilize fat stores in the active area. This, of course, is not true. Why?

Your blood supplies the nutrients and oxygen that your muscles need, and muscles cannot obtain energy from adipose tissue that just happens to be close to them. In negative caloric balance situations, fat is mobilized from areas in the reverse pattern of where it was last deposited, regardless of how the exercise is performed. So, if you put on a bit of fat in a particular area and correctly respond with exercise and diet, you will lose the fat in that area first. Likewise, the fat you have always had around your chin or stomach will be the hardest and last to trim down.

How does insulin contribute to fat gain?

Your body secretes insulin in response to a rise in blood sugar. Insulin drives the body to store the excess blood sugar as fat. Insulin inhibits your body's ability to mobilize fat out of adipose tissue and burn it as a fuel. Therefore, high insulin levels work against fat loss. Simply carbohydrates (like high-fructose corn syrup, sugar, and white flour) increase blood sugar levels the most, and increase insulin levels. Very high total-carbohydrate quantities in diets also increase insulin levels. Chronically elevated levels of insulin are responsible for metabolic syndrome, which includes obesity, Type 2 diabetes, high blood pressure, and more.