Obesity

Question 1

What are the components of daily energy expenditure?

Answer 1

o Thermic effect of feeding
o Energy expenditure of physical activity
o Resting energy expenditure

Question 2

Do people become obese because they have a slow metabolism?

Answer 2

o Some obese persons have a lower metabolic rate
o Can be caused through defects; hypothyroidism, Cushing’s syndrome (overproduction of cortisol).
o Metabolic control of appetite may go wrong
 Food intake is controlled by orosensory, gastrointestinal & neuroendocrine factors.
 Defects in these pathways may lead to dysregulation of appetite
o Individual differences in
 Diet Induced Thermogenesis
 Energy Storage (> efficient fat cells)
 Set Point Theory (Settling Point)

Question 3

Identify the cut-off points for overweight and obesity using BMI and explain the rationale for these?

Answer 3

o	BMI
	Overweight=25-29.9
	Obesity (I)=30-34.9
	Obesity (II)=35-39.9
	Obesity (III)=>40
o	Based on how many percent over normal weight
	Overweight=11-20
	Obesity (I)=21-40
	Obesity (II)=41-100
	Obesity (III)=>100

Question 4

List advantages and disadvantages of using BMI to define obesity?

Answer 4

o Advantages:
 Fairly linear correlation with body fat
 Men and women have same trend pattern
 Easy to track obesity class
o Disadvantages:
 Obesity is based on body fat, BMI doesn’t take that into account
 The correlation is not perfect, so there may be margin for error in predicting/calculating BMI
 There are gender differences

Question 5

Why is the amount of muscle mass is inversely related to CVD mortality?

Answer 5

o More muscle helps glucose sensitivity
o Protein reserves aid healing during illness
o Muscle mass contains mitochondria, thus linked to aerobic fitness

Question 6

What is obesity caused by?

Answer 6

Long-Term Positive Energy Balance

Question 7

What is the relationship between resting energy expenditure (kcal/24h) and fat-free mass (kg)?

Answer 7

Moderately positive correlation

Question 8

What is the ideal BMI (kg/m^2) value for men/women to avoid relative risk of death?

Answer 8

22/24

Question 9

What are the medical complications of obesity?

Answer 9

•	Pulmonary disease
	Abnormal function
	Obstructive sleep apnea
	Hypoventilation syndrome
•	Nonalcoholic fatty liver disease
	Steatosis
	Steatohepatitis
	Cirrhosis
•	Gall bladder disease
•	Gynecologic abnormalities
	Abnormal menses
	Infertility
	Polycystic ovarian syndrome
•	Osteoarthritis
•	Skin
•	Gout
•	Idiopathic intracranial hypertension
•	Stroke
•	Cataracts
•	Coronary heart disease
•	Diabetes
•	Dyslipidaemia
•	Hypertension
•	Severe pancreatitis
•	Cancer
	Breast
	Uterus
	Cervix
	Colon
	Esophagus
	Pancreas
	Kidney
	Prostate
•	Phlebitis
	Venous stasis

Question 10

What is the relation between obesity and diabetes?

Answer 10

• Greater prevalence of Type II diabetes in the obese
• Excess body fat leads to insulin resistance
 Adipose tissue creates demand for insulin – increase fat deposition
 Chronic high blood sugar down regulates insulin receptors
 Fats block insulin receptors, leading to insulin resistance
 Fat tissue, especially visceral fat, has a role in promoting diabetes
• Possible genetic predisposition - receptor defect

Question 11

What is the relation between obesity and hypertension?

Answer 11

• Obese individuals often have associated hypertension
• For every 10% increase in relative body weight, systolic blood pressure increases 6.5 mm/Hg,
• Hypertension is 6X more prevalent in obese individuals
• Weight gain will often lead to an increase in BP
• Unclear what causes it?
 Genetic
 Metabolic disturbance
 Diet
 Behavioural

Question 12

What is the relation between obesity and respiratory disease?

Answer 12

• Burden of excess fat on thorax makes breathing more difficult and reduces lung volume
• Hypoxia develops initially, hypercapnia can also develop - reduced respiratory drive
• Sleep apnea and snoring are common

Question 13

What is the relation between obesity and orthopaedic problems?

Answer 13

• Strong positive correlation between arthritis and obesity
• Every 5kg ↑ in weight, increased knee arthritis by 35%
• Energy cost of movement is much greater in the overfat
• Sedentariness becomes habitual leading to atrophy of muscles

Question 14

What is the impact of obesity on health?

Answer 14

• Other conditions- strokes, gall stones, some cancers (breast & colon) & reproductive problems are all increased in obese subjects.
• Mechanical- osteoarthritis, chronic low back pain & breathlessness. Sleep problems.
• Psychosocial- association with decreased psychological well-being due to social stigma

Question 15

How do you avoid high risk of mortality whilst you are fat/obese?

Answer 15

• If you are overfat then being active helps reduce risk
• Eklund 2014 study of 300K European adults
 16-30% reduction in mortality in moderately active vs inactive across BMI / Waist Circ strata
 Avoiding inactivity reduces risk of death 7%
 Avoiding being obese reduces risk of death 3.6%
• Metabolically healthy but obese (MHO) phenotype
• Should not assume just because obese they are unhealthy
• 15-30% obese are MHO
• CVD risk appears to be no higher in MHO compared to normal healthy normal weight adults
• The amount of muscle mass is inversely related to CVD mortality
 More muscle helps glucose sensitivity
 Protein reserves aid healing during illness
 Muscle mass contains mitochondria, thus linked to aerobic fitness

Question 16

How is obesity influenced by genetics?

Answer 16

• Faulty Leptin production or resistance
 Leptin a hormone, which ↓ appetite, secreted from body fat in proportion to the number of body fat stores.
 An increase in body fat causes an increase in leptin production, which suppresses intake, which should lead to a decrease in fat and therefore leptin production.
• If both parents obese, 70- 80% chance of being obese.
• Mother more critical.
• If neither parent obese, 7- 14% chance of being obese

Question 17

How is obesity influenced by metabolic factors?

Answer 17

• Some obese persons have a lower metabolic rate
• Can be caused through defects; hypothyroidism, Cushing’s syndrome (overproduction of cortisol).
• Metabolic control of appetite may go wrong
 Food intake is controlled by orosensory, gastrointestinal & neuroendocrine factors.
 Defects in these pathways may lead to dysregulation of appetite
• Individual differences in
 Diet Induced Thermogenesis
 Energy Storage (> efficient fat cells)
 Set Point Theory (Settling Point)

Question 18

How is obesity influenced by over-eating?

Answer 18

Individuals allowed to eat ad-lib diets that contain different fat levels will consume more energy on the high fat diet than on high CHO diet
 People tend to consume the same weight/volume of food at each meal & are unable to sub-consciously adapt to varying energy densities
 The same volume of a high fat (energy dense) meal will provide many more calories than the same volume of a high CHO meal

Question 19

How is obesity influenced by physical inactivity?

Answer 19

• In England, the average distance walked per person per year for transport fell from 255 miles in 1975/76 to 192 miles in 2003
• From 1971-2000 # households without a car reduced from 41% - 26%
• 20% of all journeys <1 mile are by car
• 2004: approx 70% adults drive to work, but only 6% walk
• Adults spend on average 2hrs per day watching TV
• Daily energy expenditure has decreased 250-500kcal.d-1 over last 50 years