Physiology of appetite and weight Flashcards Preview

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Flashcards in Physiology of appetite and weight Deck (36)
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1

BMI
- Calculation
- Underweight
- Normal
- Overweight
- Obese
- Morbidly obese

Calculation: Kg/ m2

Underweight: <18.5

Normal: 18.5-24.9

Overweight: 25-29.9

Obese: 30-39.9

Morbidly obese: >/= 40

2

Methods of measuring weight/ body composition

BMI

Waist circumference

Skin fold test

Bioethical impedance analysis

3

Metabolic syndrome

A group of symptoms/ signs associated with high risk of cardiovascular disease.
- Insulin resistance being the underlying factor.

Visceral obesity- central body fat
Dyslipidaemia
Hyperglycaemia
Hypertension

4

Epidemiology of obesity

Prevalence is increasing.
- 25% in England [2010-2013]

5

Mechanism behind insulin resistance and metabolic syndrome.

An increase in free fatty acids causes dyslipidemia
- Visceral fat lipolysis
- Increase in gluconeogenesis

Increase in pro-inflammatory cytokines
- TNF-alpha, IL-6 from white adipose tissue
- Decreases the expression of GLUT-4 and tyrosine kinase activity of insulin receptor

6

Adipocytokines

White adipose tissue can release a lot of pro-inflammatory cytokines
- Such as IL-6, TNF-alpha

7

Risk factors of Type 2 DM

Age
Obesity
Family history
Ethnicity [i.e south asian]

8

CVD associated with obesity

Stroke
Coronary heart disease
Hypertension
Left ventricular hypertrophy

Effects of obesity on the CVS
- Increased blood volume
- Increased blood viscosity
- Increased vascular resistance.

9

Respiratory consequences of obesity

Obstructive sleep apnoea

Hypoxia/ Hypercapnia

Pulmonary hypertension/ Right heart failure

Daytime somnolence---> Daytime accidents

10

GI/ Liver consequences of Obesity

Progresison of:
Non-alcoholic fatty liver
Non-alcoholic steatohepatits
Cirrhosis
Portal hypertension
Heptocellular cancer

Gallstones

GORD- gastroesophageal reflux disease

11

Cancer and obesity
- Prevalence
- Examples
- Mechanism

Increases risk of cancer significantly
- 10% of non-smoker cancer deaths related to obesity.

Common cancers included
- Breast
- Colon
- Endometrial
- Oesophageal
- Gall bladder
- Renal
- Thyroid

Mechanism
- Increase in insulin, IGF-1, oestrogen
- Increase in adipocytokines
- Reflux

12

Consequences of obesity on the reproductive system

Polycystic ovarian syndrome

Male hypogonadism

Adverse pregnancy outcomes

13

Consequences of obesity on the joints

Osteoarthritis

Gout

14

Consequences of obesity on mental health

Depression

Eating disorders

15

Genetic causes of obesity

Obesity associated syndromes
- Prader Willi
- Bardet Biedl
- Fragile X

Can also be polygenic
- Susceptible genes
- Inherited almost as similarly as height.

16

Stimulation of appetite

Arcuate nucleus- Lateral hypothalamus contains hunger/thirst centre.
- Can be inhibited by the satiety centre.

Activation of neurones by grehlin stimulates appetite [accelerator neurones]
- Neuropeptide Y [NPY]
- Agouti-related protein {AgRP]

AgRP can also block melanocortin receptors

Leptin acts on NPY to promote satiety.

17

Ghrelin

Hormone released from the stomach before meals
- Stimulates hunger
- Acts on hypothalamic neurones NPY, AgRP

18

Hormones that reduce appetite

CCK

GLP-1

Peptide YY [PPY]

- All peptide released rapidly after a meal.

19

Leptin

Hormone released from adipose tissue.
- Slow acting on arcuate receptors [NPY neurones]

Signals to the hypothalamus body fat %.
- Acts on satiety centre
- Negatively regulates fat mass by inhibiting hunger.
- Increases basal metabolic rate if fat mass rises.

Also important for puberty and reproduction.

20

Leptin mutations

Loss of genes encoding leptin or its receptors cause severe,, early onset obesity.
- Lack of satiety.
- Shown in Ob/ob mouse.

If receptors are fine but there is lack of leptin
- Administering leptin can reverse obesity. [shown with ob/ob mouse]

Leptin cannot be used to reverse obesity in human adults as they already have high levels of leptin.

21

Insulin and body weight

Acts on the cortex and limbic system
- Regulates bod weight by signalling body fat composition.
- Decreases food intake.

22

Brake neurones

Located in the arcuate nucleus
- ventromedial hypothalamus

Contains neurones that inhibit appetite
- Alpha-melanocyte stimulate hormone [MSH]
- POMC
- CART

These neurones can inhibit NPY and AgRP

23

Diet regulation for obesity

Eating 500-1000 cal energy deficient

Decrease portion size and snacking.

Eating more low energy dense foods
- More fruit and veg
- Less food high in sat fat and sugar.

24

Physical activity modification and Obesity

Exercising 7 days a week
- 30 min intense or 1 hr low intensity

10,000 steps a day

25

Environmental factors and obesity

Dietary intake
- Increase in energy intake
- Increase in portion size
- Cheaper cost of food.

Decease in physical activity
- Car ownership and Tv ownership show positive trend with obesity.

26

Targets for lifestyle modification

10% of weight loss
- Continue until ideal weight is reached
- 1-2 lbs/ 0.5-1kg loss a week

Problems
- 5-10% weight loss takes a year to achieve
- Yo-yo dieting

27

Orlistat
- Mechanism of action
- Indications
- Adverse effects

Action
- Inhibits pancreatic and and gastric lipases
- Prevents hydrolysis of TG into FFA and glycerol.
- Prevents absorption of dietary fat.

Indications
- Obesity

Adverse effects- associated with fat malabsorption
- Loose/ liquid stools
- Faecal urgency
- Anal discharge
- Fat-soluble vitamin deficiency [ADEK]

28

Problems with using pharmacological therapy in obesity

Only increases 5% weight loss by 3-4 fold.

Weight gain occurs when treatment is stopped.

29

Laproscopic adjustable banding [Gastric banding]

Restrictive surgery
- Reduces diameter of the stomach
- Allows reduced dietary intake and improves satiety.

30

Roux-en-Y gastric bypass

Restrictive and malabsorptive surgery
- Bypasses the duodenum into the jejunum and reduces stomach size
- Alters gut hormones and bile acid flow
- Improves satiety

Complications
- Micronutrient deficiences
- Dumping syndrome