L11 Physiology of appetite and weight Flashcards
What methods can be used to measure weight?
BMI Waist circumference Skin-fold thickness Bioelectrical impedance analysis Ethnicity specific cut-offs
What are the BMI measurements?
<18.5 - underweight
18.5 - 24.9 - overweight
30-39.9 - obese
≥40 - morbidly obese
What is the definition of obesity?
A BMI above 30 kg/m2
What are some consequences of obesity?
Metabolic syndrome Type II diabetes Cardiovascular disease Respiratory disease Liver disease Cancer Reproductive dysfunction Joint problems Psychological morbidity
What is metabolic syndrome?
Cluster of closely - associated cardiovascular risk factors
What is metabolic syndrome associated with?
BMI > 30 Visceral obesity Dyslipidaemia Hyperglycaemia Hypertension
What is the underlying pathophysiology of metabolic syndrome?
Insulin resistance
Increased free fatty acids
Pro-inflammatory cytokines
What are the risk factors for type II diabetes mellitus?
Age
Obesity
Family history
Ethnicity
Why is the prevalence of type II diabetes mellitus increasing?
Ageing population
Increasing obesity which is becoming more common in younger population
Increased detection / diagnosis
Increased survival
Describe cardiovascular disease
Metabolic syndrome plus:
- Increased blood volume & blood viscosity
- Increased vascular resistance
- Increased hypertension
- Increased left ventricular hypertrophy
- Increased coronary artery disease
- Increased stroke
Describe respiratory disease
Obstructive sleep apnoea
Hypoxia / hypercapnia
Pulmonary hypertension
Describe GI / liver disease
Non-alcoholic fatty liver
Non-alcoholic steatohepatitis
Gallstones
Reflux
What can non-alcoholic fatty liver and steatohepatitis progress to?
Cirrhosis
Portal hypertension
Hepatocellular cancer
What types of cancers can be caused by obesity?
Breast Endometrial Oesophagus Colon Gallbladder Renal Thyroid
What are the mechanisms of cancer associated with obesity?
Increased insulin Increased free IGF-1 Increased oestrogen Adipo-cytokines Reflux
What are the symptoms of PCOS?
Oligomenorrhoea
Hirsutism
Acne
What are the consequences associated with PCOS?
Subfertility
Endometrial hyperplasia
Insulin resistance
What are some of the effects of obesity on the reproductive system?
PCOS
Male hypogonadism
Adverse pregnancy outcomes
What is the effect of obesity on joints?
Osteoarthritis
Gout
What are the psychological effects of obesity?
Depression
Eating disorders
Describe the genetic causes of obesity
Rare: obesity-associated syndromes such as Prader-Willi and Bardet-Biedl
Common: polygenic, susceptibility genes, heritability of weight
Describe the environmental causes of obesity
Diet: high fat, low sugar, socioeconomic factors
Physical activity: 20-50% of total energy expenditure, socioeconomic factors
Describe the relevance of the gut microbiome in obesity
Differences in gut bacteria between those with obesity / type II DM and health individuals
Transplantation of faecal matter alters insulin sensitivity
Describe the role of leptins in obesity in the human
A leptin deficiency or mutation of the leptin receptor can cause obesity
Increased leptin concentration is associated with increased fat
Possibly leptin resistant
Possible decrease in CNS transport of leptin
What does CCK do?
Induces satiety which inhibits eating
What does ghrelin do?
Induces eating
What does PYY do?
Inhibits eating for up to 12 hours
Describe changes in diet to help lower weight
Diet 500-1000kcal energy deficiency Low energy density: decreased saturated fat, decreased sugar, increased fruit and veg Decreased portion sizes Decreased snacking Structured meals / meal replacements
Describe changes to physical activity to help lower weight
Exercise 7 days a week - 30 min moderate / high intensity - 60 min low intensity 10,000 steps per day Exercise will increase health regardless of weight loss
Describe the mechanism of orlistat
Binds and inhibits lipases in lumen of the gut
Prevents hydrolysis of dietary fat into absorbable free fatty acids / glycerol
Excrete 1/3 dietary fat
What are the adverse effects of orlistat?
Flatulence, oily faecal leakage, diarrhoea
Decreased absorption of fat-soluble vitamins
What is the best 1st line agent for overweight / obese patients with T2DM?
Metformin
Describe laparoscopic adjustable banding
Restrictive only
Inject / withdraw saline to adjust diameter of the band
Describe roux-en-Y gastric bypass
Restrictive
Malabsorptive
Alterations in gut hormone and bile acid flow which contribute to weight loss
What are some consequences that can occur due to roux-en-Y gastric bypass?
Micronutrient deficiencies
Dumping syndrome
What are the disadvantages of surgical treatment for obesity?
Perioperative mortality / morbidity
Long-term follow up
Some weight re-gain
Expensive
Describe the NICE guidelines for bariatric surgery in 2006
After failure of other options if:
-BMI > 40kg/m2
- BMI > 35 with co-morbid conditions
First line if BMI >50
Describe NICE guidelines for bariatric surgery in T2DM
Expedite bariatric surgery if BMI > 35
Consider surgery if BMI > 30
Describe the NICE guidelines for bariatric surgery in 2013
Must have been obese for at least 5 years
Must engage with non-surgical weight loss programme for 12-24 months first
