Physiology of appetite and weight Flashcards
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
Methods of measuring weight/ body composition
BMI
Waist circumference
Skin fold test
Bioethical impedance analysis
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
Epidemiology of obesity
Prevalence is increasing.
- 25% in England [2010-2013]
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
Adipocytokines
White adipose tissue can release a lot of pro-inflammatory cytokines
- Such as IL-6, TNF-alpha
Risk factors of Type 2 DM
Age
Obesity
Family history
Ethnicity [i.e south asian]
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.
Respiratory consequences of obesity
Obstructive sleep apnoea
Hypoxia/ Hypercapnia
Pulmonary hypertension/ Right heart failure
Daytime somnolence—> Daytime accidents
GI/ Liver consequences of Obesity
Progresison of: Non-alcoholic fatty liver Non-alcoholic steatohepatits Cirrhosis Portal hypertension Heptocellular cancer
Gallstones
GORD- gastroesophageal reflux disease
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
Consequences of obesity on the reproductive system
Polycystic ovarian syndrome
Male hypogonadism
Adverse pregnancy outcomes
Consequences of obesity on the joints
Osteoarthritis
Gout
Consequences of obesity on mental health
Depression
Eating disorders
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.
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.
Ghrelin
Hormone released from the stomach before meals
- Stimulates hunger
- Acts on hypothalamic neurones NPY, AgRP
Hormones that reduce appetite
CCK
GLP-1
Peptide YY [PPY]
- All peptide released rapidly after a meal.
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.
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.
Insulin and body weight
Acts on the cortex and limbic system
- Regulates bod weight by signalling body fat composition.
- Decreases food intake.
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
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.
Physical activity modification and Obesity
Exercising 7 days a week
- 30 min intense or 1 hr low intensity
10,000 steps a day
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.
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
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]
Problems with using pharmacological therapy in obesity
Only increases 5% weight loss by 3-4 fold.
Weight gain occurs when treatment is stopped.
Laproscopic adjustable banding [Gastric banding]
Restrictive surgery
- Reduces diameter of the stomach
- Allows reduced dietary intake and improves satiety.
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
Advantages of bariatric surgery
Significant weight loss
- 25-30%
Resolves/ Improves co-morbities
- Cost effective in the long term.
Disadvantages of bariatric surgery
Perioperative mortality/ morbidity
Long term follow-up
- Micronutrient deficiencies
Weight regain
Expensive
Bariatric surgery guidelines
NICE
For T2 DM recent onset
- Proceed if BMI > 35
- Consider if BMI >30
For obese, after failure of other options
- First line if BMI> 50
- BMI> 40
- BI> 35 with co-morbidities
Bariatric surgery guidelines
NHS England
Same as NICE but
- Obese for at least 5 years
- Must engage with non-surgical weight loss programme for 12-24 months
Metformin and obesity
Increases insulin sensitivity
- Increases peripheral glucose uptake
- Inhibits gluconeogenesis
Prevents hyperglycaemia
Weight loss from lifestyle interventions
5-10%
