HNSC 1210 - CHAPTER 9

We need three lifestyle components to achieve a healthy body weight:

- diet - physical activity - behavior modification

Factors that affect the BMR; Environmental temperature

Adjusting to either heat or cold raises the BMR.

Appetite

is the psychological desire to eat. It is a learned motivation and a positive sensation that accompanies the sight, smell or thought of appealing foods

Leptin

- A hormone produced by adipose (fat) cells that acts as a satiety factor in regulating appetite. - an appetite suppressing hormone that is produced in the fat cells. - conveys information about body fatness to the brain, working to suppress appetite and food intake between meals. - also produced in the stomach.

Drawbacks to BMI:

- Fails to show how much weight is actually fat - Fails to show where the fat is located - It is not suitable for certain groups: Some athletes, Pregnant and lactating women, and adults over 65

What is a disadvantage of Bioelectric Impedance (BIA)

- Fluctuations in the body's water content can impact results - Water conducts electrical charge, so over hydration can underestimate body fatness, and dehydration can overestimate body fatness.

Estimated Energy Requirement (EER) Calculations should take the following into account to ensure a more accurate result:

- Gender: because body composition differs between men and women, which will affect energy requirements - Age: because energy requirements decrease as we age - Height and weight: because energy requirements are higher for those taller or heavier - Physical activity level: because physical activity will use more energy

We expend energy in three ways:

- To fuel the body's basal metabolic rate (BMR) - To fuel voluntary activity - Through the body's metabolic response to` food (the thermic effect of food)

Selected theories of metabolic causes of obesity

- enzyme theory - fat cell number theory - set-point theory - thermogenesis I: energy-wasting proteins and brown fat theory - thermogenesis II: adaptive thermogenesis theory - thermogenesis III: diet-induced thergenesis theory

Three Methods of Assessing Body Fatness; Radio-graphic techniques

- give images of body tissues and an assessment of body composition. - Eg. Dual energy X-ray absorptiometry (DEXA), which measures two beams of x-ray energy as they pass harmlessly through body tissue - These beams differentiate between fat-free soft tissue, fat tissue and bone tissue - Therefore they provide a precise measurement of total body fatness and the distribution of the fat - Disadvantages are that it is very expensive, and it may not represent an accurate picture in extremely obese individuals - body fatness may be overestimated in those with a thick body shape.

Three Methods of Assessing Body Fatness; Density

- is a measure of body weight compared to volume - Lean tissue is denser than fat, therefore, the denser a person's body is, the more lean tissue it must contain - Density can be determined either by underwater weighing or by air displacement methods.

Bioelectric Impedance (BIA)

- measures how well a tiny, harmless electrical charge is conducted through the body - The idea is that the charge will conduct better in a body with more lean tissue - A disadvantage is that fluctuations in the body's water content can impact results - Water conducts electrical charge, so over hydration can underestimate body fatness, and dehydration can overestimate body fatness.

Three Methods of Assessing Body Fatness; Conductivity

- measures the body's ability to conduct an electric current - Only lean tissue and water conduct electrical current - Bioelectric impedance (BIA) measures how well a tiny, harmless electrical charge is conducted through the body - The idea is that the charge will conduct better in a body with more lean tissue - A disadvantage is that fluctuations in the body's water content can impact results - Water conducts electrical charge, so over hydration can underestimate body fatness, and dehydration can overestimate body fatness.

BMR (basal metabolic rate)

- the sum of all involuntary activities necessary to maintain life (e.g., circulation, respiration, temp maintenance, hormone secretions, nerve activities, and new tissue synthesis). It excludes digestion and voluntary activities. - varies from person to person.

3500 calories is equal to how many lbs?

1 lb

Besides gender and age, standards differ because of lifestyle factors and stage of life:

1. Competitive endurance athletes may have lower body fat than average. They need just enough body fat to provide fuel for their activity, insulate the body and allow for fat-soluble hormone activity 2. Northern fishermen want higher body fat to insulate against the cold 3. During pregnancy the outcome can be compromised if a women starts pregnancy with too much or too little body fat. If body fat is too low, some individuals become infertile, and some individuals with high body fat also have difficulty getting pregnant.

Three Methods of Assessing Body Fatness

1. density 2. conductivity 3. radiographic techniques

The minimum calorie level typically recommended is _____ calories per day for women, _____ calories per day for men. Below this calorie level, it becomes difficult to meet the DRI recommendations for nutrients.

1200; 1500

What is the maximum recommended body fat for men under 40 years?

22%

What is the maximum recommended body fat for men over 40 years?

25%

What percentage of energy expenditure does voluntary/physical activity have?

25-50%

What is the maximum recommended body fat for women under 40 years?

32%

What is the maximum recommended body fat for women over 40 years?

35%

Recommendations for a Weight-Loss Diet; Total fat

35% or less of total Calories

If a child has one parent who is obese, their chance of becoming obese is __-__%

40-70

What percentage of energy expenditure does thermic food effect have?

5-10%

What percentage of energy expenditure does BMR have?

50-65%

Recommendations for a Weight-Loss Diet; Carbohydrate

55% or more of total Calories

Recommendations for a Weight-Loss Diet; Saturated fatty acids

8% to 10% of total Calories

Recommendations for a Weight-Loss Diet; Cholesterol

<300 mg per day

Recommendations for a Weight-Loss Diet; Protein

Approximately 15% of total Calories

Recommendations for a Weight-Loss Diet; For people with BMI between 27 and 35

Approximately 300 to 500 Cal per day reduction from usual intake

Recommendations for a Weight-Loss Diet; For people with BMI ≥35

Approximately 500 to 1,000 Cal per day reduction from usual intake

Drawbacks to BMI: Why is it is not suitable for certain groups? Adults over 65?

BMI values are based on data collected from younger people. Also, people tend to lose height as they age. Adjusted BMI ranges for older adults exist with normal BMI ranging from 23-29.

Fat cell number theory

Body fatness is determined by both the number and the size of fat cells. Fat cells increase in number during the growing years, tapering off in adulthood. Fat cell number may increase more rapidly in obese children than in lean children, leading to a lifelong tendency toward obesity.

Factors that affect the BMR; Growth

Children and pregnant women have higher BMRs.

Enzyme theory

Excess fat storage may stem from elevated concentrations of an enzyme, lipoprotein lipase (LPL), that enables fat cells to store triglycerides. The more LPL, the more easily fat cells store lipid, and the more likely the body will remain obese. The fat cells of obese people contain more LPL than the fat cells of lean people and therefore reach a large size quickly.

Define visceral fat

Fat stored in the abdominal cavity associated with an increased risk of disease (e.g. CVD, diabetes, stroke, hypertension).

Voluntary activity

Intentional activities such as walking, sitting, running, etc. conducted through voluntary muscle movements.

Thermogenesis II: Adaptive thermogenesis theory

Many tissues, such as muscle, spleen, and bone marrow, convert stored energy into heat in response to cold temperature, physical conditioning, overfeeding, starvation, trauma, and other stress. Heat is also produced to "waste" fuel without useful work when energy supplies are too high; conversely, with low energy supplies, energy is conserved. Genetic inheritance is thought to determine the efficiency of this system. Dieters' efforts are often thwarted when, on reducing food intake, metabolism slows and heat production diminishes.

A BMI of ≥ 40 is considered ______.

Obese Class III

A BMI of 30.0-34.9 is considered ______.

Obese class I

A BMI of 35.0-39.9 is considered ______.

Obese class II

Thermogenesis I: Energy-wasting proteins and brown fat theory

Proteins control the body's heat production, or thermogenesis. A type of adipose tissue, brown fat, has abundant energy-wasting proteins that specialize in converting energy to heat. Although regular white fat cells have a sluggish metabolism and conserve and store fat energy, brown fat cells actively metabolize fat, releasing its stored energy as heat. Brown fat is more abundant in lean animals than in fat ones, and this theory states that a person with more brown fat and therefore more energy-wasting proteins may stay leaner. Human infants have abundant brown fat, but the amount dwindles with age.

What are the "stop mechanisms" that signal the body to cease/refrain from eating?

Satiation and Satiety

Factors that affect the BMR; Height

Tall people have a larger surface area, so their BMRs are higher.

Factors that affect the BMR; Age

The BMR is higher in youth; as lean body mass declines with age, the BMR slows. Continued physical activity may prevent some of this decline.

Set point theory

The body may "choose" a weight it wants to be and defend that weight by regulating behaviours and metabolic activities. Just as a thermostat setting triggers a heater to run when air temperature falls and turn off when warmth is restored, whenever weight is lost or gained, the set-point mechanism changes metabolic energy expenditure to restore the "chosen" body weight. The theories of thermogenesis, below, explain possible mechanisms by which the body defends its set point.

Thermic Effect of Food (TEF)

The body's metabolism speeds up for approximately five hours after a meal.

Factors that affect the BMR; Body composition

The more lean tissue, the higher the BMR. A typical man has greater lean body mass than a typical woman, making his BMR higher.

Thermogenesis III: Diet-induced thergenesis theory

The thermic effect of food varies between obese and nonobese people. In lean people who have just eaten a meal, energy use speeds up for a while, but in many obese people, no change in energy use occurs after eating. In theory, this small difference in energy expenditure may account for an accumulation of body fat, but no studies have shown this conclusively. Overweight people often spend more energy each day than lean people do because their heavier bodies require more energy to move and maintain.

Factors that affect the BMR; thyroxine

The thyroid hormone ________ is a key BMR regulator; the more this is produced, the higher the BMR.

Recommendations for a Weight-Loss Diet; Polyunsaturated fatty acids

Up to 10% of total Calories

Recommendations for a Weight-Loss Diet; Monounsaturated fatty acids

Up to 15% of total Calories

Factors that affect the BMR; Stress

_____ hormones raises BMR

Factors that affect the BMR; Fasting/starvation

_____/_____ hormones lower the BMR.

Define Body Mass Index (BMI)

a measure of body weight relative to height; used to evaluate a person's health risks associated with being underweight and overweight

When identical twins are raised apart in households that differ in lifestyle factors such as smoking, eating habits, nutrient intake and physical activity, their weight is often more similar to their adoptive or biological parents lifestyle habits. So this shows that although genetics plays a role in a person's tendency towards becoming obese, lifestyle factors determine whether this tendency is fulfilled.

adoptive

Factors that affect the BMR

age, height, growth, body composition, fever, stress, environmental temperature, fasting/starvation, malnutrition, thyroxine

Drawbacks to BMI: Why is it is not suitable for certain groups? Some athletes?

because muscle mass weighs more then fat. Therefore, athletes may have a higher BMI, although their total body fat may be quite low (e.g., body builders - their BMI is often in the obese range)

Bioelectric Impedance (BIA); charge will conduct _______ in a body with more lean tissue

better

Adopted children's weight is typically more similar to their biological OR adoptive parents

biological

Those who carry their weight around the ______ of their body around the stomach (central obesity, apple-shape) have a higher risk of death from all causes compared to those who carry their weight around the ______ body (pear-shape).

center; lower

When body fatness _________ leptin production _________ and appetite _________.

decreases; decreases; increases

Lean tissue is ______ than fat, therefore, the denser a person's body is, the more _______ tissue it must contain

denser; lean

When energy intake ________ energy expenditure, excess fat accumulates in the fats cells.

exceeds

Define subcutaneous fat

fat stored directly under the skin

Leptin operates on a ________ mechanism

feedback

The ideal amount for health depends on ______ and on ______.

gender; age

What are the "go" mechanisms that stimulate eating?

hunger and appetite

Drawbacks to BMI: Why is it is not suitable for certain groups? Pregnant and lactating women?

increased weight is normal during childbearing

As body fatness ________, more leptin is produced in an attempt to ________ food consumption and result in fat loss.

increases; lower

Hunger

is a physiological need to eat. It is an unpleasant sensation that demands relief, a drive to obtain food

In a majority of cases of obesity, genetics may cause a tendency towards obesity; however is OR is not the only determinant.

is not

What is a disadvantage of dual energy x-ray absorptiometry (DEXA)?

it is very expensive, and it may not represent an accurate picture in extremely obese individuals - body fatness may be overestimated in those with a thick body shape.

For most people, basal metabolism accounts for the _________ energy expenditure, followed by voluntary activity and the thermic effect of food.

largest

fat standards differ because of ______ factors and ______ of life:

lifestyle; stage

Fat/skin fold test

measures the thickness of a fold of skin at areas on the body using calipers. Often the back of the arm, below the shoulder blade or skin from the waist is tested and compared to standards; provides an estimate of total body fat and where that fat is located. It should be done by a trained technician and ideally should be done by the same technician if having the test repeated

dual energy x-ray absorptiometry (DEXA)

measures two beams of x-ray energy as they pass harmlessly through body tissue - These beams differentiate between fat-free soft tissue, fat tissue and bone tissue - Therefore they provide a precise measurement of total body fatness and the distribution of the fat - Disadvantages are that it is very expensive, and it may not represent an accurate picture in extremely obese individuals - body fatness may be overestimated in those with a thick body shape.

Waist circumference

measures visceral fatness and disease risk. You measure around the body at a point near the belly button. The person should exhale normally when the measurement is taken. A higher measurement can indicate an increased risk of disease even if BMI is normal.

A BMI of 18.5-24.9 is considered ______.

normal weight

A BMI of 30.0 and over is considered ______.

obese

A BMI of 25.0-29.9 is considered ______.

overweight

So it is better to be ______ shaped then ______ shaped.

pear; apple

The accuracy of the results really depends on the skills of the clinician performing the test. If you are going back for a repeat test, it is ideal to have the same/different clinician perform the test.

same

Healthy weight loss is slow OR fast weight loss, aiming for __-__ lbs per week. Studies show that it is easier to _____ slow weight loss.

slow; 1-2; sustain

It is also better to take your current diet and make big OR small changes to help to facilitate weight loss. This becomes a lifestyle change that you are more likely to continue with throughout your life

small

Define Estimated Energy Requirement (EER)

the average dietary energy intake that maintains energy balance and good health in a person of a given age, gender, weight, height, and level of physical activity

Energy balance occurs when...

the calories coming into our body equal the calories that our body is expending

Satiation

the perception of fullness that builds throughout a meal, eventually reaching the degree of fullness/satisfaction that stops eating. Generally determines how much food is consumed in one sitting

Satiety

the perception of fullness that lingers after a meal, inhibiting eating until the next meal. Generally determines the length of time between meals.

Identical twins raised apart in similar households are more likely to weigh different OR the same then fraternal twins.

the same

Define anthropometry

the scientific study of the measurements and proportions of the human body; Direct body measurements (e.g. waist circumference, fat fold test).

Factors that affect the BMR; malnutrition

this lowers the BMR.

Factors that affect the BMR; Fever

this raises BMR

Bioelectric Impedance (BIA); water conducts electrical charge, so over hydration can ________ body fatness, and dehydration can ________ body fatness

underestimate; overestimate

Three Methods of Assessing Body Fatness; Density can be determined either by ______ ______ or by ______ ______ methods.

underwater weighing; air displacement

A BMI of <18.5 is considered ______.

underweight

Body Mass Index (BMI) equation is...?

weight (kg) / height (m^2)

What is a healthy waist circumference?

women <35 inches (88 cm) men < 40 inches (102 cm)