Obesity background

Nomenclature

In general, there is persistent hunger that is not satiated by the amounts of food that satisfy the non-obese
- This leads to long-term positive energy balance, and accumulation of adipose tissue
- Adipose tissue eventually develops reduced ability to assimilate excess calories
- This leads to fat redistribution to other tissues, causing diverse health consequences
Metabolic actions of adipose tissue
- Increased secretion of 'adipokines' - leptin, adiponectin, resistin and inflammatory cytokines - comes from white fat, as opposed to brown fat
- Causes chronic low-grade inflammation, interfering with cellular processes, leading to metabolic derangements (T2DM, etc)
Ghrelin - the 'hunger hormone'
- Levels decrease after meals
- Acts on hypothalamus
- Primarily produced in fundus of stomach
- Regulates hunger together with leptin
Genetic
- Specific genes - FTO, MC4R - however these only rarely are the sole cause of obesity, and generally become apparent in childhood.
- Syndromes - Prader-Willi (deficits in ghrelin signalling)
Microbiome
- May be a relationship between gut microbiome and obesity, suggested by some animal studies
Nutrition
- Hypoalbuminaemia
- Vitamin and micronutrient deficiencies are common
Weight regain
- Body defends fat vigorously
- Increased hunger, driven by ghrelin
- Decreased energy expenditure, driven by multifactorial neurohormonal changes including reduced SNS input

Not necessarily directly correlated with BMI
Predicts mortality
- Large BMI people may even be lower risk mortality than normal
Do not assume that larger BMI = harmful = need for treatment

Cardiovascular
- HTN
- MI
- Cardiomyopathy
- DVT
- Pulmonary HTN
- Right heart failure
Pulmonary
- OSA (35-94% amongst morbidly obese) - benefit from CPAP/BiPAP post-op to avoid hypoxia
- Hypoventilation syndrome of obesity (Pickwickian syndrome)
  - Generally seen BMI >60
  - Plethoric face, maybe clinically cyanotic, with difficulty at mild exertion
  - High haematocrit and PaCO2 > PaO2
  - Elevated pulmonary artery pressure
- Asthma
Metabolic
- Metabolic syndrome
- T2DM (see in 20-30% of bariatric surgery patients)
- Hchol/hyperlipidaemia
GIT
- GORD
- Cholelithiasis
- NASH cirrhosis - benefit from caloric restriction pre-op
MSK
- Degenerative joint disease
- Lumbar disc disease
- Osteoarthritis
- Ventral hernias
Genitourinary
- Stress urinary incontinence
- CKD (diabetes and HTN)
Gynaecologic
- Menstrual irregularities
Skin/integumentary system
- Fungal infections
- Boils/abscesses
Oncologic
- Cancer of thyroid, prostate, oesophagus, kidney, stomach, colon, rectum, GB, pancreas, breast, ovaries, cervix, and endometrium
Neurologic/psychiatric
Social