Chapter 7: Energy Balance Flashcards
What is considered a normal BMI? Underweight? Overweight? Obese?
Underweight = <18.5 Normal = 18.5-24.9 Overweight = 25 - 29.9 Obese = 30+
What is BMI?
Body Mass Index
weight/height^2
What are some consequences of obesity? (6 things)
1) Type-2 Diabetes
2) Cardiovascular Disease
3) Cancer (colon & breast)
4) Joint Disorders
5) Gall Bladder Disease
6) Sleep Apnea
What is obesity (cellular level)?
increase in size of adipose cells
What does an increase in size of adipose cells lead to?
1) Increase in FFA
2) Increased inflammation
Obesity increases the risk of the following 9 cancers:
1) Colorectal
2) Breast (postmenopausal)
3) Endometrial
4) Kidney
5) Esophageal
6) Pancreatic
7) Liver
8) Gallbladder
9) Gastric
What is cancer?
a series of genetic mutations that result in a cell that…
a) de-differentiates (no longer functions as intended)
b) becomes proliferative (grows uncontrollably)
c) can not repair its damaged DNA
d) becomes resistant to apoptosis (programmed cell death)
What is apoptosis?
method the body uses to get rid of damaged cells it cannot repair
Which two hormones are often associated with cancer development?
1) Insulin
2) Estrogen
What role does insulin play in cancer development?
a) stimulates the growth of cells
b) suppresses apoptosis
What role does estrogen play in cancer development? In what state is breast cancer more likely?
a) stimulates growth of breast tissue (& of breast tumours in postmenopausal women)
b) “free” estrogen (not bound to SHBG) is more bioavailable –> more stimulation of cell growth
What are the two ways in which estrogen circulates in the blood?
1) Bound to sex hormone binding globulin (SHBG) –> less stimulation of cell growth
2) Free estrogen - not bound to SHBG –> more stimulation of cell growth
In what two ways are cancer and obesity linked?
1) Obesity –> increase in adipose tissue mass –> increased synthesis of estrogen in adipose tissue –> increase in free estrogen –> increase in cell proliferation and decrease is apoptosis in breast cells –> tumour development
2) Obesity –> increase in FFA release –> insulin resistance –> increase in insulin –> decrease in apoptosis and increase in cell proliferation in colon cells & decrease in SHBG in liver (which leads to increase in free estrogen in 1) –> tumour development
Is there an association between BMI and colon cancer risk?
YES
- BMI of >25 –> increasing risk of colon cancer
Is there an association between BMI and breast cancer risk?
YES
BMI of >25 –> increasing risk
What is gall bladder disease?
- excessive production of cholesterol in the liver
- deposition of solid cholesterol in gall bladder
- sometimes a consequence of rapid weight loss (rapid loss increases cholesterol synthesis)
What is sleep apnea?
- interruptions of breathing during sleep –> poor sleep & excessive fatigue during the day
- fatty tissue in neck compress the airway & block airflow
What are two joint disorders often associated with obesity?
1) Osteoarthritis
2) Gout
What is osteoarthritis? How is obesity a contributing factor?
- breakdown of cartilage that cushions the joins
- weight increases risk b/c of excessive pressure on joints
What is gout? How can obesity be a contributing factor?
- uric acid deposition in joints
- increased risk with insulin resistance (caused by obesity)
What is weight stigmatization?
- negative attitudes, mistreatment & discrimination based on weight status
- particularly towards the obese
What percentage of people who attempt weight loss fail?
90%
Why is body weight important to health? (2 things)
1) unhealthy body weight associated w. increased health risk
2) weight stigmatization
What is a positive energy balance?
when energy content of food consumed is greater than energy content expended for metabolism & physical activity
(leads to weight gain)
What is a negative energy balance?
when energy content of food consumed is less than energy content expended for metabolism & physical activity
(weight loss)
What is energy balance?
when energy content of food consumed is equal to energy content expended for metabolism & physical activity
(weight maintenance)
What is a bomb calorimeter?
- an instrument used to determine the amount of energy in food
- the rise in the temperature of water is used to calculate kcal of food (combustion)
- it is correct for both available & unavailable components of food (ex. dietary fibre)
How is food energy converted into ATP? (5 steps)
1) Glycolysis converts glucose –> pyruvate, pyruvate –> acetyl CoA
2) Beta-oxidation breaks fatty acids down to acetyl CoA
3) Amino acids are deaminated
4) Breakdown products of glucose, fatty acids, and amino acids enter the citric acid cycle
5) Energy from electrons are used to make ATP
What is total energy expenditure (TEE)?
- a measurement of total amount of energy expended, takes into account:
i) basal metabolism
ii) physical activity
iii) non-exercise thermogenesis
What is basal metabolism?
- energy req’d for involuntary processes needed to support life
- expressed as basal metabolic rate: kcal expended/unit of time
How may someone’s basal metabolic rate be affected?
- decreases with weight loss (an adaptation for starvation)
What is the average percentage of the TEE that basal metabolism takes up?
60-75%
What is the average percentage of the TEE that physical activity takes up?
15-30% of TEE
What is non-exercise activity (thermogenesis)?
- heat generated by non-intentional exercise (ex. fidgeting)
- expressed as thermic effect
What is the average percentage of the TEE that thermogenesis takes up?
10% of TEE
Where is glycogen stored in the body?
- liver
- muscle
Where is glucose (FFA) stored in the body?
- bodily fluids
Where are triglycerides stored in the body?
- adipose tissue
Where is protein stored in the body?
- muscle
How much glycogen is stored in the body?
1400 kcal (24 hr supply of glucose)
How much triglyceride is stored in the body?
115,000 kcal (57 day supply)
Stored triglycerides reflect the _____ composition of the diet.
fatty acid
How is energy expended in the body?
1) Cellular metabolism
2) Systemic level (maintains function of vital organs, fuels physical activity & absorption of food)
3) Dietary fats stored when there is a positive energy balance
What is an EER?
estimated energy requirement
Which variables are involved in calculating EER?
1) age
2) physical activity level
3) weight
4) height
note: formula changes depending on gender
What is lean tissue?
fat-free mass (i.e. muscle, bone, all tissue except fat)
What is sarcopenia?
loss of muscle mass with aging
What is the average percentage of body fat that a baby should have? An adult woman? Adult man?
baby: 12% body fat
adult woman: 21-32%
adult man: 8-19%
Which factors are used to asses healthy body weight/body composition?
1) BMI
2) Waist circumference (visceral fat)
Which location of fat is associated with highest health risk?
visceral fat (central obesity)
What are the limitations of BMI?
- if you have a high % of lean body mass you will also have a high BMI
- not suitable for pregnant/lactating women
- must be used in combination with waist circumference
What is visceral fat?
- fat located behind the abdominal muscle layer
- measured as waist circumference
What health risks may visceral fat contribute to? How?
1) type-2 diabetes
2) heart disease
a) releases FFAs readily
b) prone to becoming insulin-resistant
c) releases proteins that promote inflammation
How is food intake regulated?
1) Short term –> Ghrelin, CCK, & GLP1
2) Long term –> Leptin & Insulin
How is energy expenditure regulated?
1) Adaptive Thermogenesis
2) NEAT (Non-exercise activity thermogenesis)
What is hunger?
- internal signals that stimulate someone to acquire & consume food
What is satiety?
- feeling of fullness & satisfaction caused by food consumption
- eliminates the desire to eat
- experienced after a meal
- determines when the next meal will occur
What is satiation?
- feeling of fullness that develops during a meal
- determines when a meal will end
How may genes play a role in body characteristics? (2 things)
1) Obesity Genes
- affect the regulation of (i) food intake, (ii) energy expenditure, (iii) fat metabolism
2) Set-Point Theory
- genetically pre-determined body weight that tends to be defended (after weight loss ppl tend to return to their pre-weight loss weight)
Which hormone stimulates hunger? How?
GHRELIN
- secreted by the stomach
- stimulates eating at set times
- levels in the blood rise before a meal, stimulating hunger
- levels in blood decline after a meal, reducing hunger
Which hormone(s) suppresses hunger? How?
CHOLECYSTOKININ (CCK)
- released when chyme enters the small intestine
- suppresses food intake
Other suppressing hormones:
- Peptide PYY
- GLP-1 (also stimulates insulin release)
How does ghrelin release differ between obese and lean individuals?
after a meal, ghrelin levels do not decline as much in obese individuals as they do in lean individuals, which may result in prolonged eating
How do GLP-1 levels differ between lean & obese individuals?
- levels tend to be lower in obese than in lean individuals
- may increase the length of a meal
What is leptin?
- hormone secreted into the blood by adipose tissue
- levels are directly proportional to amount of adipose tissue; more fat –> more leptin secreted
- acts on the hypothalamus of the brain to regulate food intake
- presence of leptin reduces food intake, absence stimulates hunger
How do leptin levels differ between lean & obese individuals?
- levels are higher in obese than in lean individuals
* absence of leptin is a stronger signal to promote hunger than the presence of leptin is to suppress hunger
What happens to leptin levels during weight loss?
DECREASE
What happens to leptin resistance during weight loss?
DECREASES
What effects do the changes in leptin levels & leptin sensitivity have on food intake?
INCREASE
What is leptin resistance?
- insensitivity to the “stop eating” signal of leptin
- a consequence of high fat mass
What role does insulin play in long term regulation of energy balance?
- acts on the hypothalamus (just like leptin)
- suppresses food intake
- absence of insulin stimulates extreme hunger (ex. type-1 diabetes)
How do insulin levels differ between lean & obese individuals?
- higher in obese individuals
- obese individuals are at higher risk for developing insulin resistance, which will suppress the “stop eating” signal
How does obesity contribute to insulin resistance?
- Increased FFA
- Increased Inflammation
How may genes contribute to obesity?
1) Thrifty metabolism –> combination of genes that may alter metabolism
2) Adaptive thermogenesis –> body’s ability to increase/decrease energy expenditure up to 250kcal
- over-eating leads to an increase in expenditure, undereating leads to conservation of energy
How does adaptive thermogenesis occur?
1) futile cycling –> opposing metabolic pathways occur simultaneously
2) uncoupling of electron transport chain from ATP synthesis –> production of heat rather than ATP
- occurs in brown adipose tissue (most adult adipose tissue is white)
How does adaptive thermogenesis differ between lean & obese individuals?
- decline in BMR, in response to weight loss, is more pronounced in obese individuals
- increase in BMR, in response to weight gain, is less pronounced in obese individuals
What are the 2 main factors that are making Canadians fatter?
1) genes –> well-adapted to protect us from starvation
2) lifestyle –> obesogenic environment (i.e. overeating, sedentary behaviour…)
What are the 3 clinical practice guidelines for treatment of obesity?
1) Reduce weight by 10% over 6 months –> improves serum lipids, blood pressure, blood glucose
2) Gradual rate of weight loss to avoid loss of muscle (0.5-1kg/week –> 500-1000 kcal deficit/day)
3) Avoid weight cycling
What are some of the key differences between healthy diets and fad diets?
Healthy diets…
1) meet nutrient needs, incl. variety of foods, suits food preferences, can be maintained throughout life
2) promote a change in behaviour, teaches new habits and provides social support
3) are based on sound scientific principles & may include monitoring by qualified health professionals
What are the ABCs of behaviour (re: CBT)?
1) Antecedents (cues) that lead to the behaviour
2) Behaviour itself
3) Consequence
What is Orlistat? How does it aid in weight loss?
- a drug designed to treat obesity
- does not allow lipase to enter mucosal cell of small intestine
- thus, triglycerides are not digested, and are excreted in feces
What is a gastric bypass? How does it aid in weight loss?
- surgical treatment of obesity
- reduces stomach size by stapling off a large section
- -> less absorption of food b/c small intestine is bypassed
What are some complications of gastric bypass?
1) “dumping syndrome” - micronutrient deficiencies b/c less food contents are being absorbed
2) food enters small intestine too rapidly & causes serious symptoms (ex. diarrhea, nausea, etc..)
* meals must be small & eaten slowly
What is the difference between direct calorimetry, indirect calorimetry, and doubly-labelled water?
- all measure energy expenditure
1) Direct calorimetry –> measures amount of heat produced when either (i) a food is combusted in a bomb calorimeter, or (ii) given off of the human body (heat is proportional to amount of energy used)
2) Indirect calorimetry –> compares amount of oxygen consumed w. amount of carbon dioxide exhaled by breathing into a mouthpiece/mask
3) Doubly-labelled water –> (most practical) measures disappearance of heavy isotopes of hydrogen & oxygen in bodily fluids after consumption of a defined amount of water labelled w. both isotopes
What is the relationship between doubly-labelled water and the equations shown in Table 7.5?
Measurements of energy expenditure using doubly-labelled water have been used to develop these equations for estimating EERs
What are the 3 different methods for determining body composition?
1) Underwater weighing –> weighing on land & in water; difference b/w these two masses = fat-free mass
2) Skinfold thickness –> measurement of subcutaneous fat with calipers, taken from standard locations (ex. triceps)
3) Bioelectrical impedence (most popular) –> measures body fat by directing a low-energy electric current through the body & calculating resistance to flow
