Obesity

Question 1

What happens when weight is stable

Answer 1

When weight stable

E in = E out + E stored

Question 2

What happens in weight gain

Answer 2

Weight gain

E in exceeds E out
Increase intake
Decrease expenditure

Question 3

When does obesity occur

Answer 3

Obesity can only occur when energy intake remains higher than energy expenditure for an extended period of time.
Excess energy intake is stored as fat

Question 4

When is fat detrimental

Answer 4

In excess

Question 5

What is meant by energy homeostasis

Answer 5

Energy homeostasis = in a steady state, the energy intake must equal the energy expenditure.

Question 6

What is total energy expenditure equal to

Answer 6

Heat produced + work on environment ( at rest all energy expenditure is equal to heat produced that is thermogenesis)

Question 7

What can daily energy expenditure be split into

Answer 7

The RMR (RMR-sum of the sleeping metabolic rate and energy cost of arousal) which represents 50-70% of daily EE
    RMR correlates best with fat free mass, and therefore RMR generally correlates with body 

The thermic effect of food, which represents 5-15 %of daily EE
The energy cost of physical activity (sum of spontaneous PA and unrestricted/voluntary physical activity), which represents 20-40% of daily EE.

Question 8

Why is it harder to lose weight the more you lose

Answer 8

§ REE is proportional to lean fat body mass (LBM) and so 100kg people may have 2800 REE while 80kg may have 2000 REE.
o This means its much harder to lose weight the more you lose – i.e. first 10kg easier than next 10kg.

Question 9

What does BMR correlate with

Answer 9

BMR correlates with body weight. Reason is because the increase in weight is not just fat, usually about 25% is lean tissue - comprising heart, skeletal muscle, enlargement of digestive tract and liver.
Cases of obese patients with low BMR have yet to be found.
Energy expended on a fixed activity is always higher for people carrying extra weight, so total EE in obese persons is generally higher than lean.

Evidence that low levels of PA are a familial trait, which may predispose to obesity.

Question 10

Describe a different view of the equation

Answer 10

Looking at the equation in a different way – the enegy expenditure sie of the eqn can be subdivided into obligatory EE – which is what all cells of the body need to maintain function – this forms between 50-70% of EE in humans.

Adapytive thermogenesis covers the energy converted into heat as a result of body temperature regulation – not particularly important in humans since we have methods to counteract these changes in temperature ie. Clothes and heating within buildings etc.

The majority of energy expenditure is in the form of REE/BMR and so exercise etc. will only affect a small portion of our energy expenditure (while REE represents like 65-70%).

Question 11

Describe adaptive thermogenesis

Answer 11

variable, regulated by the brain
responds to temperature and diet
occurs in adipocyte mitochondria, skeletal muscle and other sites

Question 12

Describe the use of BMI to measure energy stores

Answer 12

o Weight & height measurements – i.e. BMI (2530 = obese).
§ Note – measurements of BMI have different ranges depending on ethnicity (Asians lower bounds).
§ Also be aware the muscle weighs more than fat and so the values may be misleading.

Question 13

List the range for BMI

Answer 13

18.5 Underweight
18.5-24.9 Healthy weight
25–29.9 Overweight
30-34.9 Obese (class1 obesity)

35-39.9 Severe obesity (class 2 obesity)

40-50 Morbid obesity (class 3 obesity)
50-60 Super obesity
>60 Super-morbid obesity

Question 14

How do the values of BMI differ for Asian populations

Answer 14

<18.5			Underweight
18.5-22.9 	Healthy weight
23-24.9		Pre-obese (overweight)
25-29.9		Obese 
> 30			Severe obesity

Question 15

What was BMI derived from

Answer 15

Life insurance tables- how much they cost the health service

Question 16

Describe another method for assessing energy stores

Answer 16

o Regional adiposity/energy partitioning.
§ Central adiposity is much more strongly associated to CVD.
§ “Waist: hip” ratio – Associated to the “Metabolic Syndrome”
§ Now in the UK, around 65% of the population is ‘overweight’ and so it is ‘normal’ to be overweight.

Question 17

Describe the situation in 2004

Answer 17

In 2004, 10% 6- 10 year old boys and girls
5% of 11-15 year old boys, and 11% of 11-15 year old girls are obese.

Across the under 20 age group as a whole, 10% of females and 8% males are obese.

If we include those who are overweight and obese this is 35% for females and 28% for males.

These figures do not include any adjustment to allow for bias in non-respondents to the survey and may actually under-represent the proportion of obese teenagers.

Question 18

Describe obesity as a disease of ageing

Answer 18

As we age, the proportion of people who are overweight and obese increases

Question 19

What happens to people who gain weight at key measuring points

Answer 19

Hard to stop their path- they will become overweight or obese

Question 20

What does genetic background predict

Answer 20

Risk to the environment- environment is a major factor for change

Question 21

Describe the impact of obesity for the low-middle income countries

Answer 21

Devastating
problems with malnutrition and now also the complications of obesity (T2DM, hypertension)- more strain on the health system

Question 22

Summarise the epidemiology of BMI in the UK

Answer 22

Highest in age group 55-64
Ethnic groups – highest in Caucasian and Bangladeshi1
Regional variation – Scotland and North England highest2
Smokers: lower BMI but greater central obesity3
Higher in social class 5 – men and women1

Question 23

Describe the variation of BMI amongst smokers and different ethnic groups

Answer 23

Smokers – data on WHR that smoker, despite being leaner than non-smokers, have more central obesity than non-smokers.
The highest WHR among smokers was found to be dose dependent, being greatest in those smoking 20 or more cigs / day.

Ethnic Group –Varies depending on age. BMI not found to be higher in different ethnic groups, but we know that south asians are more likely to have abdominal obesity and a higher risk of developing type 2 DM.

Question 24

Describe the genetic contribution to obesity

Answer 24

60% inheritable but explain only 5% of obesity

Question 25

Describe the impact of obesity on non-communicable diseases

Answer 25

Obesity drives most of the non-communicable diseases (T2DM, cancer, hypertension)- affects every field of medicine

Question 26

List the Orexigenic / anabolic molecules

expressed by genes in the CNS

Answer 26

Neuropeptide Y (NPY)
Agouti gene related peptide (AGRP)
Agouti-related transcript (ART)
Melanin-concentrating hormone (MCH)
Dopamine

Question 27

List the Anorectic / catabolic molecules

expressed by genes in the CNS

Answer 27

Leptin receptor (LEPR)
Pro-opiomelanocortin (POMC)
Melanocortin receptor 4 (MCR4)
Corticotropin releasing hormone (CRH)
Serotonin receptor subtype 2C (5-HT2C)
Glucagon-like peptide 1 receptor (GLP-1R)

Question 28

Describe the Prentice and Jebb studies

Answer 28

Prentice and Jebb have graphically documented two indicators of inactivity (hours per week of TV viewing and cars per household) against the current secular trend in obesity in Britain. A strong relationship exists.

At the same time, similar data for total energy consumption and fat intake show downward trends (bad science- didn’t take into account food consumed between meals).

Points convincingly towards reduced energy expenditure, as a result of increased availability of labour saving devices, as a major contributor to obesity.

Numerous studies show that those who remain active or increase their physical activity level, or perhaps more importantly who reduce their sedentary pursuits like tv viewing

TV viewing is a surrogate for daily activity- linked to weight gain over time

Question 29

What do our genes protect against

Answer 29

Malnutrition- appetite regulation
excess energy is new
survival was eating food in contact- and to use the energy efficiently
this works against us in an environment of excess energy as we store it

Question 30

Describe the regulation of feeding

Answer 30

Average human eats 900,000 kcals per year.

A 0.02% error would result in an extra 3500 kcals per year
This would result in an extra 1lb weight gain per year

Question 31

Describe the economic costs of obesity

Answer 31

Costs of treating obesity £49m
Other direct costs of up to £1.2bn 
	(2.6% of total NHS budget)
Other indirect costs of up to £1.07bn
Premature mortality accounts for £1.1bn
Sickness absence accounts for 18m days/yr 
	(= up to £1.45bn)

Total direct + indirect costs = up to £3.7bn
(= 42% increase in just 6 years)

The Foresight report (Oct07) - cost estimates suggest that by 2022 the costs of obesity may increase by up to £30bn per year

Question 32

Describe the link of obesity to other medical conditions

Answer 32

Obesity is known to lead to both chronic and severe medical problems.
Biggest killer – coronary heart disease
Biggest impact on morbidity and quality of life – diabetes
Ostearthritis – weight bearing joints
Infertility: in women as PCOS and men are more likely to be impotent
Cancers: breast, endometrial

Question 33

Describe IHD

Answer 33

This is the main cause of premature death among the obese.

Hypertension, coronary thrombosis and congestive heart failure are all significantly commoner among obese people than normal weight control

Obese women are over 3 times more likely to have an MI cf. Non-obese women.
And both men and women are twice as likely to experience angina.

Question 34

Describe T2DM

Answer 34

Obese people are up to 80 times more likely to develop diabetes than those who are of a normal weight.

Question 35

Describe the link between obesity and cancers

Answer 35

breast, endometrial, stomach, and colon.

Obesity is thought to increases risk of developing cancer primarily through its effect on hormones

Question 36

Describe the link between obesity and gallstones

Answer 36

Formed when the bile contains too much cholesterol or bilirubin or not enough bile salts, or when the gall bladder does not empty properly.
Increasing weight – increased prevalence

Question 37

Describe the link between obesity and osteoarthritis

Answer 37

Hips, knees and spine.

Overweight adults are more than twice as likely as their peers to devlelop osteoarthritis in their hips and knees.

Question 38

Describe the link between obesity and mental health

Answer 38

Obese women – less likely to be hired
More likely to have their performance rated negatively
Less likely to be promoted
Depression

Question 39

What else is obesity linked to

Answer 39

Sleep apnoea
Infertility
Gout