Physiology of appetite and weight Flashcards Preview

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Flashcards in Physiology of appetite and weight Deck (35)
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1
Q

Obesity measurements

A

BMI

Waist circumference

Skin fold thickness

Bioelectrical impedance analysis

Ethnicity specific cut offs

2
Q

Medical problems associated with obesity

A

Metabolic syndrome/ type 2 diabetes

Cardiovascular disease

Respiratory disease

Liver disease

Cancer

Reproductive dysfunction

Joint problems

Psychological morbidity

3
Q

Metabolic syndrome

A

Constellation of closely associated CV risk factors

  • visceral obesity
  • dyslipidaemia
  • hyperglycaemia
  • hypertension

Insulin resistance is the underlying pathophysiological mechanism

4
Q

Pathophysiology of insulin resistance and the metabolic syndrome

A

Increased free fatty acids

Lipolysis of visceral fat

Glucoenoegenesis

Dyslipidaemia

5
Q

Pro-inflammatory cytokines and insulin resistance resistance and the metabaolic syndrome

A

TNF-a, IL 6

Leads to increased insulin resistance

Decreased expression of GLUT-4 (insulin sensitive glucose transporter)

Decreased tyrosine kinase activity of insulin receptor

6
Q

CV disease

A

Metabolic syndrome and

  • increased blood volume and blood viscosity
  • increased vascular resistance
  • increased hypertension
  • increased left ventricular hypertrophy
  • increased coronary artery disease
  • increased stroke
7
Q

Respiratory disease

A

Obstructive sleep apnoea

Hypoxia/ hypercapnia

Pulmonary hypertension
- right heart failure

Accidents
- daytime somnolence

8
Q

GI/ liver

A

Non-alcoholic fatty liver

Non-alcoholic steatohepatitis

May progress to cirrhosis, portal hypertension, hepatocellular cancer

Gallstones

Reflux

9
Q

Cancer

A

10% cancer deaths in non-smokers attributable to obesity

Types of cancer include: breast, endometrial, oesophagus, colon, gall bladder, renal, thyroid

Mechanisms include: increased insulin, increased free IGF-I, increased oestrogen, adipo-cytokines, reflux

10
Q

Reproductive system

A

Polycystic ovarian syndrome

  • oligomenorrhoea, hirsutism, acne
  • subfertility
  • endometrial hyperplasia
  • insulin resistance

Male hypogonadism

Adverse pregnancy outcomes

11
Q

Joints

A

Osteoporosis

Gout

12
Q

Psychological

A

Depression

Eating disorders

13
Q

Genetics of obesity

A

Rare

  • obesity associated syndromes
  • Prader-Willi
  • Bardet- Biedl

Common

  • polygenic
  • susceptibility genes
  • heritability of weight/ height
14
Q

Other causes of obesity

A

Hypothyroidism

Cushing’s syndrome

15
Q

Environmental causes: diet

A

High fat

High sugar

Socio-economic factors

16
Q

Environmental causes: physical activity

A

20-50% total energy expenditure

Obesity prevalence related to proxy measures of physical activity

Socio-economic factors

17
Q

Fetal programming

A

Stimuli/ insults at critical periods have persistent biological effects

Stressors in utero

  • undernutrition, trace elements
  • crudely represented by birth weight

Mechanism: epigenetic modification of gene expression

18
Q

Life course model

A

Factors operating at every stage of life affect health outcomes later in life

Pathway of risk between events and health outcomes

Worst outcomes associated with:

  • low birth weight
  • excessive weight gain in infancy
  • adult obesity
19
Q

Gut microbiome

A

10^4 cells/g in jejunum to 10^14 cells in colon

Integral to host homeostasis

  • absorption of nutrients
  • reabsorption of bile acids
  • fermentation of fibre and bile acid metabolism

Influenced by diet
- high fat, high fibre

Influence disease risk
- obesity, T2 diabetes

20
Q

Slow acting hormones that regulate body weight

A

Leptin

Insulin

Signal % body fat to hypothalamus

  • decrease food intake
  • increase energy expenditure
21
Q

Rapid acting peptides that regulate meal sizes

A

Released from GI tract

  • cholecystokinin: decreases eating
  • ghrelin: increased eating
  • PYY: decreases eating (up to 12 hours)

Act via hypothalamus

22
Q

Accelerator neurones

A

NPY/ AgRP neurones

Neuropepetide Y: increases eating

AgRP: blocks melanocortin receptor

23
Q

Brake neurones

A

POMC neurones

Melanocortin peptides
- a-MSH, CART: decrease eating

24
Q

Leptin

A

Starvation signal

Permissive effect on puberty/ reproduction

Obese humans

  • very rare: leptin deficiency, mutation of leptin receptor
  • usually: increased leptin with increased fat, decreased CNS leptin transport
25
Q

Lifestyle modification: diet

A

500-1000 kcal energy deficiency

Low energy density

  • decreased sat fat, decreased sugar
  • increased fruit and veg

Decreased portion sizes and snacking

Structured meals/ meal replacements may help promote greater weight loss

26
Q

Lifestyle modification: physical activity

A

Exercise 7 days/ week

Target 10000 steps/ day

Regardless of weight/ weight loss, exercise increases health

27
Q

Orlistat mechanism

A

Binds and inhibits lipase in the lumen of the gut

Prevents the hydrolysis of dietary fat into absorbable free fatty acids/ glycerol

Excrete 1/3rd dietary fat

28
Q

Adverse effects of orlistat

A

Flatulence, oily faecal leakage, diarrhoea

Decreased absorption fat soluble vitamins (ADEK)

29
Q

Metformin

A

Best 1st line agent for over weight/ obese patients with T2 diabetes

All other oral hypoglycaemic agents and insulin cause weight gain

Used in diabetes prevention trials but not licensed for this use

30
Q

Laparoscopic adjustable banding

A

Restrictive only

Inject/ withdraw saline to adjust the diameter of the band

31
Q

Roux en- Y gastric bypass

A

Restrictive

Malabsorptive

Alterations in gut hormones and bile acid flow contribute to weight loss

Micronutrient deficiencies
- supplement with iron, B12, folate, calcium, vitamin D

Dumping syndrome
- GI and vasomotor symptoms

32
Q

Advantages of surgical treatment

A

Weight loss 25-30%

Resolve or improve co-morbidities
- brings cost savings

33
Q

Disadvantages of surgical treatment

A

Perioperative mortality/ morbidity

Long term follow up

Some weight re-gain

Expense

34
Q

NICE guidelines for bariatric surgery 2014

A

Recent onset T2DM

Expedite bariatric surgery if BMI>35

Consider surgery if BMI > 30

35
Q

NHS England 2013 bariatric guidelines

A

As per NICE but

  • must have been obese for at least 5 years
  • must engage with non-surgical weight loss programme for 12-24 months first