Aspects of Obesity

Question 1

basal metabolism

Answer 1

the obligatory consumption of energy to keep the body functioning at rest

Question 2

thrifty genotype

Answer 2

one that is evolved to live in an evironment where food was not plentiful

enables individuals to efficiently collect and process food to deposit fat during periods of food abundance in order to provide for periods of food shortage

Question 3

what co-morbidities are there in obesity that are simply related to inreased fat mass

Answer 3

OA, back pain, asthma, sleep apnoea

Question 4

describe the link between diabetes and obesity

Answer 4

obese people are resistant to the actions of insulin (more is produced as more is eaten), this causes a compensatory rise in insulin as the pancreas tries to overcome the resistance

eventually the pancreas can no longer keep up, and the patient becomes hyperglycaemic and develops diabetes

Question 5

obesity and inflammation

Answer 5

• Obesity is a proinflammatory condition in which hypertrophied adipocytes and adipose tissue-resident immune cells both contribute to increased circulating levels of proinflammatory cytokines
• There is an obesity associated state of chronic low-grade systemic inflammation.

Question 6

what is the primary function of adipose tissue

Answer 6

• store excess nutrients and release FFA during fasting through ß oxidation
• also contain various immune cells

Question 7

what are proteins and peptides secreted by adipocytes called

Answer 7

adipokines

Question 8

name some adipokines

Answer 8

leptin, adiponectin, inflammatory mediators

oestrogen, cortisol and FFA

Question 9

the functions of adipocytes and macrophages in obesity

Answer 9

share several overlapping functions (eg secrete cytokines and store fat), although some are quite distinct

in obesity, adipocytes secrete cytokines and macropahges accumulate fat becoming foam cells (found in atheroscerotic plaques)

Question 10

what happens to the adipokines in obesity

Answer 10

• Adipose tissue from lean individuals preferentially secretes anti-inflammatory adipokines e.g. adiponectin. These mediate physiological functions.
• In contrast, obese adipose tissue mainly releases proinflammatory cytokines e.g. TNF alpha, angiotensin II. These modulate insulin resistance.

Question 11

adiponectin

Answer 11

• anti inflammatory cytokine
• secretion reduced in obestiy
• It is a protein hormone involved in regulating glucose levels and fatty acid breakdown
• Reduction of adiponectin is associated with atherosclerosis and dyslipidaemia.

Question 12

cellular stress in adipocytes

Answer 12

the ER in adipocytes cannot cope with the increased metabolic demands due to an expanding fat mass - activates pathways that in the short term cause inflammation

these same pathways in the longer term can lead to insulin resistance (diabetes) and hyperlipidaemia (atherosclerosis)

Question 13

leptin

Answer 13

• one of the main secretions of adipose tissue
• Secreted from adipocytes proportionally to fat cell mass
• Acts on the brain to decrease food intake, increase energy expenditure and influence glucose and lipid metabolism.

Question 14

leptin in obesity

Answer 14

In obese subjects, leptin levels are increased, with little or no impact to regulate energy homeostasis – leptin resistance.

Question 15

what are the features of high and low leptin

Answer 15

high - decreased appetite and increased thermogenesis

low - increased appetite and decreased thermogenesis

Question 16

why can leptin not be used as an anti obesity drug

Answer 16

if one has plenty of fat stores, leptin has a flat dose response curve

Question 17

what is the mainstay of every weight loss programme

Answer 17

diet

many morbidly obese patients have little capacity to exercise

Question 18

hypocaloric diet

Answer 18

calories consumed < calories used

Question 19

what is defined as a very low calorie diet

Answer 19

<800 calories/day

Question 20

what is the most important determinant of success with dietary interventions

Answer 20

compliance

Question 21

Orlistat

Answer 21

inhibits lipases to block absorption of dietary fat over a certain level

up to one third of digested fat is excreted into the faeces - steatorrhoea

Question 22

what must Orlistat always be prescribed in the context of

Answer 22

hypocaloric diet

Question 23

bariatric definition

Answer 23

deals with the causes, treatment and prevention of obesity

Question 24

who is eligible for bariatric surgery

Answer 24

BMI >40

BMI >35 with co-morbidities

Question 25

gastric banding

Answer 25

purely restrictive means that the stomach holds less food, one eats less and feels full quicker it is the simplest surgical operation, but is the most prone to complications eg band slipping, especially when patients lose a lot of weight

Question 26

sleeve gastrectomy

Answer 26

also restrictive significantly reduces capacity in terms of eating

Question 27

gastric bypass

Answer 27

both restrictive and malabsorptive

Question 28

what must always be performed post bariatric surgery

Answer 28

nutritional assessments

Question 29

what causes more weight loss - conservative treatment or bariatric surgery

Answer 29

bariatric surgery also huge improvements in post op hyperglycaemia

Question 30

resting metabolic rate

Answer 30

* amount of energy expended at rest - minimum energy consumption * eg amount of energy required to perform basal functions

Question 31

what contributes to RMR

Answer 31

fat and fat free (eg muscle) mass

Question 32

describe the relationship between RMR and weight loss

Answer 32

* RMR is higher in obesity and falls with weight loss - it is the amount of energy required to perform basal functions * however, it falls more than one would expect with the weight loss * it is as if the body perceives the weight loss as a threat to survival * = adaptive thermogenesis acts as a brake on further weight loss

Question 33

with reference to RMR, why is bariatric surgery more effective

Answer 33

less adaptive thermogenesis

Question 34

with reference to RMR, why is it harder for some people to lose weight

Answer 34

essentially, the lower the RMR, the harder it is to lose weight people have different RMR

Question 35

define adaptive thermogenesis

Answer 35

Adaptive thermogenesis is defined as the decrease in energy expenditure beyond what could be predicted from body weight or its components (fat-free mass and fat mass) under conditions of standardized physical activity in response to a decrease in energy intake.

Question 36

BMI thresholds

Answer 36

Underweight: \<18.5 Increased risk: 23-27.5 High risk: ≥27.5

Question 37

waist circumference thresholds

Answer 37

men≥ 94 women ≥80

Question 38

what are thresholds values for BMI and waist circumference in asian populations

Answer 38

lower

Question 39

risk with relative BMI

Answer 39

Question 40

definition of weight status in children - centile cut offs

Answer 40