Physiology of Appetite and Weight Flashcards
1
Q
What are the various measurements of obesity?
A
- Body mass index (BMI) kg / m2
- < 18.5 underweight
- 18.5-24.9 normal
- 25-29.9 overweight
- 30-39.9 obese
- ≥40 morbid obesity
- Waist circumference
- Skin-fold thicknesses
- Bioelectrical impedance analysis
- Ethnicity specific cut-offs
2
Q
What are the medical problems associated with Obesity?
A
- Metabolic syndrome / type 2 diabetes
- Cardiovascular disease
- Respiratory disease
- Liver disease
- Cancer
- Reproductive dysfunction
- Joint problems
- Psychological morbidity
- the higher the BMI the greater the percentage of patients with co-morbidities
3
Q
What is metabolic syndrome?
A
- a constellation of closely associated CV risk factors
- Visceral obesity
- Dyslipidaemia
- Hyperglycaemia
- Hypertension
- Insulin Resistance is the underlying pathophysiological mechanism
4
Q
What is the epidemiology of Type 2 DM?
A
- Risk is determined by
- Age, Obesity, Family History, Ethnicity
- Prevalent in
- the rich in poor countries
- in the poor in rich countries
5
Q
What does CV disease cause
A
All the following are increased
- blood volume and blood viscosity
- vascular resistance
- hypertension
- left ventricular hypertrophy
- coronary artery disease
- stroke
6
Q
How is the respiratory system effected in obesity?
A
- Obstructive sleep apnoea
- Hypoxia / hypercapnia
- Pulmonary hypertension
- Right heart failure
- Accidents
- Daytime somnolence
7
Q
how does obesity effect the GI/ Liver
A
- Non-alcoholic fatty liver
- Non-alcoholic steatohepatitis
- May progress to cirrhosis, portal hypertension, hepatocellular cancer
- Gallstones
- Reflux
8
Q
Wha is the prevalence of cancer in obesity?
A
- ~ 10% cancer deaths in non-smokers attributable to obesity
- Types of cancer include
- Breast, endometrial, oesophagus, colon, gall bladder, renal, thyroid
- Mechanisms include
- increase insulin, increase free IGF-I, increase oestrogen,
- adipocytokines, reflux
9
Q
How does obesity effect the reproductive system?
A
- Polycystic ovarian syndrome
- Oligomenorrhoea, hirsutism, acne
- Subfertility
- Endometrial hyperplasia
- Insulin resistance
- Male hypogonadism
- Adverse pregnancy outcomes
10
Q
How are joints affected by obesity?
A
- Osteoarthritis
- Gout
11
Q
What psychological effects of obesity?
A
- Depression
- Eating disorders
12
Q
What are the genetic components of obesity?
A
- Rare
- obesity-associated syndromes
- Prader-Willi
- Bardet-Biedl
- obesity-associated syndromes
- Common
- Polygenic
- Susceptibility genes
- Heritability of weight ~ heritability of height
13
Q
What are other causes of obesity?
A
- Hypothyroidism
- Cushing’s syndrome
14
Q
How does the environment contribute to obesity?
A
- High fat
- High sugar
- ‘Coca-colonization’ of developing world
- Socio-economic factors
- 20-50% total energy expenditure
- Obesity prevalence related to proxy measures of physical activity
- Car ownership
- TV viewing
- Socio-economic factors
- Social Networking
15
Q
Explain Fetal programming and it’s relation to obesity
A
- ‘Programming’: stimuli /insults at critical periods have persistent biological effects
- ‘Stressors’ in utero
- ?undernutrition, ?trace elements, ?other
- crudely represented by birth weight
- Mechanism: epigenetic modification of gene expression
- Example:
- ‘Programmed’ adrenal axis overactivity in adulthood
- Causal factor for metabolic syndrome
- Increased vulnerability to coronary heart disease
16
Q
How does the ‘Life Course Model’ explain obesity?
A
- factors operating at every stage of life affect health outcomes later in life
- there is a ‘pathway of risk’ between events and health outcomes
- the ‘worst outcomes’ are associated with:
- low birth weight
- excessive weight gain in infancy/childhood
- adult obesity
17
Q
What role does the Gut Microbiome play in Obesity and T2 Diabetes
A
- Differences in gut bacteria
- can be induced by diet e.g high-fat diet
- Transplantation of faecal material alters insulin sensitivity
- mice and humans
18
Q
How are weight and appetite regulated?
A
- slow-acting hormones that regulate body weight
- Leptin
- Insulin
- Signal % body fat to the hypothalamus
- decrease food intake
- increase energy expenditure
- Rapid-acting peptides that regulate meal sizes are released from GI tract
- CCK: decreases eating
- Ghrelin: increases eating
- Peptide YY (PYY): decreases eating (up to 12 hours)
- they act via the hypothalamus
19
Q
How does the Hypothalamus control appetite?
A
Via the Arcuate nucleus
Increases eating
- NPY (Neuropeptide Y)
- increases eating
- AgRP neurons
- Blocks melanocortin receptor
Decreases eating
- POMC neurons
- Melanocortin peptides
- alpha-MSH, CART
20
Q
What is Leptins role in Obese humans?
A
- usually acts as a starvation signal
- Obesity rarely caused by
- leptin deficiency
- mutation of leptin receptor
- Obesity usually caused by
- increased leptin with increased fat
- potentially leptin resistant
- potentially decreased CNS leptin transport
21
Q
Review this overview of how appetite is controlled
A
22
Q
What pathways could be taken to control/ treat obesity?
A
- Lifestyle modification
- Pharmacological
- Surgical
- Public health/ Societal
23
Q
What Lifestyle modifications need to be made?
A
- Diet
- 500-1000 kcal energy deficiency
- low energy density: decrease sat fat & sugar, increase fruit and veg
- decreased portion sizes, decreased snacking
- Structured meals/ meal replacements
- Physical activity
- exercise 7 days/wk
- 30 mins moderate-high intensity or 60 mins low intensity
- target 10,000 steps/day
- exercise 7 days/wk
24
Q
What is a VLCD and what are it’s outcomes in T2 DM patients?
A
- a very low-calorie diet used in patients diagnosed with T2DM <6 yrs prior
- VLCD (830kcal/day) for 3-5 months
- initially, total diet replacement with formulae
- stepped food introduction
- long term maintenance with structured support
Outcomes
- 12 month outcomes reported
- 24% of participants achieved 15 kg weight loss or more
- 46% induced remission of T2DM
- Normal HbA1c off all medication for 2 months
- >10 kg weight loss: 73% remission
25
What are the usual targets and problems with Lifestyle Modification?
* USUAL TARGETS
* 10% weight loss (¹ ideal weight)
* 1-2 lb (0.5 – 1 kg) per week
* Some evidence that ‘ambitious’ goals promote more weight loss
* PROBLEMS
* Most patients can achieve ~ 5-10 % weight loss / 1 year
* ‘Yo-yo’ dieting / regaining weight lost
* ‘Obesogenic environment’
* Weight loss results in increased hunger, increased satiety, increased metabolic rate
* BEST HOPE
* Sustainable lifestyle changes
* Diet combined with exercise / physical activity
* Ongoing management is required to maintain weight loss
26
What is the Mechanism of Orlistat?
* BInds & inhibits lipases in the lumen of the gut
* prevents the hydrolysis of dietary fat into absorbable free fatty acids/ glycerol
* Excrete ~1/3 of dietary fat
27
What are the adverse effects of Orlistat?
* Flatulence, oily faecal leakage
* Diarrhoea
* decreased absorption of fat soluble vitamins
* vit. ADEK
* take supplements
28
What is the indication of Metformin?
* 1st line agent for over-weight/ obese patients with Type 2 diabetes
* all other oral hypoglycaemic agents and insulin causes weight gain
* used in diabetes prevention trials
* recommended by NICE for prevention of T2DM in adults at high risk
29
What surgical treatment can be done to treat obesity?
* Laparoscopic adjustable banding
* restrictive only- inject/withdraw saline to adjust the diameter of the band
* Roux-en-Y gastric bypass
* Restrictive
* increased satiety
* malabsorptive
* micronutrient deficiencies: iron, B12, folate, Ca++, Vit D
* alteration in gut hormones and bile acid flow contribute to weight loss
* causes dumping syndrome
30
What are the pros and cons of surgical treatment?
_Advantages_
* weight loss 25-30%
* resolves or improve co-morbidities
_Disadvantages_
* Perioperative mortality/morbidity
* depends on the procedure and experience of the surgeon
* Long-term follow-up
* micronutrient deficiencies
* Some weight re-gain
* patients will still be obese
* Expense
* cost-effective after some time depending on co-morbidities
31
What are the NICE guidelines for bariatric surgery?
NICE 2006
* After failure of other options if
* BMI \> 40 kg/m-2
* BMI \> 35 with co-morbid conditions
* Or first line
* BMI \> 50 kg/m-2
NICE 2014
* Recent onset T2DM:
* Expedite bariatric surgery if BMI \> 35
* Consider surgery if BMI \> 30
32
What are the NHS guidelines on bariatric surgery
NHS England 2013
* 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
33
What are Public Health/ Societal approaches to tackling obesity?
* Schools
* PE, lunches, vending machines
* Urban design
* Marketing/ media/ social media
* food labelling, food advertisements
