L11 - Appetite and Weight Flashcards
Measurements that can be done
BMI (kg/m^2 Waist circumference Skinfold thickness Bioelectrical impedance analysis Ethnicity specific cut offs
Epidemiology in UK
stabilised at 25% between 2010-13
What are the associated health problems with obesity?
Metabolic syndrome, T2 diabetes, CVS disease, Resp disease, liver disease, cancer, reproductive dysfunction, joint problems, psychological morbidity
Metabolic syndrome
what is it?
What is the underlying pathophysiological mechanism?
group of closely related CV risk factors: Visceral obesity Dyslipidaemia Hyperglycaemia Hypertension
Insulin resistance
Obesity
How can it be described / measured
BMI vs body fat distribution
—–Central vs peripheral
Metabolic syndrome associated with
- —Central (visceral) fat
- —BMI > 30
T2 Diabetes Mellitus
risk is determined by what
why is the prevalence increasing
Age, obesity, family history, ethnicity
↑Age population, ↑ obesity (T2 younger), ↑ detection / diagnosis, ↑survival with T2 DM
CV Disease
what happens with this
Metabolic syndrome AND ↑blood volume and blood viscosity ↑ vascular resistance ↑ hypertension ↑ left ventricular hypertrophy ↑ coronary artery disease ↑ stroke
respiratory system - how can this be associated with obesity
Obstructive sleep apnoea
Hypoxia / hypercapnia
Pulmonary hypertension - right heart failure
Accidents - daytime somnolence
Cancer
what types of cancer are associated with obesity
What is the mechanism of this
10% cancer deaths in non smokers attributable to obesity
Types: breast, endometrial, oesophagus, colon, gall bladder, renal, thyroid
Mechanisms: ↑ insulin, ↑ free IGF-I, ↑ oestrogen, apido-cytokines, reflux
Reproductive system
how is this associated with obesity
Polycystic ovarian syndrome:
- —Oligomenorrhoea, hirsutism, acne
- —Subfertility
- —Endometrial hyperplasia
- —Insulin resistance
Male hypogonadism
Adverse pregnancy outcomes
Joints
how are these associated with obesity
Osteoarthritis
Gout
Psychological
how are these associated with obesity
Depression
Eating disorders
Genetics of obesity
RARE:
Obesity associated syndromes
Prader-Willi
Bardet-Biedl
COMMON
Polygenic
Susceptibility genes
Heritability of weight ~ heritability of height
Other causes of obesity
hypothyroidism
Cushing’s syndrome
Environmental factors of obesity
Diet: high fat and sugar, ‘coca-colonisation’ of developing world, socio-economic factors
Physical activity: 20-50% total energy expenditure, obesity prevalence related to proxy measures of physical activity (car ownership, TV viewing), socioeconomic factors
Fetal programming
what is it, how and why can this cause obesity
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
Life course model
what is it and why can this happen
Factors operating at every stage of life affect health outcomes later in life
PATHWAY OF RISK between events and health outcomes
Worst outcome: associated with low birth weight, excessive weight gain in infancy / childhood, adult obesity
Gut microbiome
what can it be influenced by and what can it influence and alter and how
Influenced by diet
Influence disease risk: Obesity, T2 diabetes etc
Differences in gut bacteria can be induced by diet etc high fat diet
Faecal transplant alters insulin sensitivity
What hormones regulate body weight and how
leptin , insulin
slow acting
signal % body fat to hypothalamus
decr food intake and ↑ energy expenditure
What peptides regulate meal sizes
where are they released what do they act on
Released from GI tract
Cholecystokinin (CCK) - decr eating
Ghrenlin - ↑ eating
PYY – ¯ eating up to 12 hrs
Act via hypothalamus
Leptin
what happens with it in mice and humans
deficiency in mice causes obesity
In humans has permissive effect on puberty
very rare for humans to have leptin deficiency / receptor mutation
usually incr in leptin with incr in fat
Lifestyle modification for obese patients: DIET
200-1000 kcal energy deficiency
low energy density
decr sat fat an d sugar
incr fruit and veg
decr portion sizes and snacking
structured meals / meal replacements may help promote weight loss
Lifestyle modification for obese patients: PHYSICAL ACTIVITY
7 days a week 30 min moderate-high intensity 60 low intensity target 10,000 steps in increasing 500 step increments
VLCD and T2 DM
what are usual targets
what are the problems for obese people to loose weight
10% weight loss
0.5-1kg per week
evidence that more ambitous goals promote weight loss
PROBLEMS:
most can achieve 5-10% weight loss but yo yo dieting / regaining weight lost
also obesogenic environment
weight loss results in hunger and decr in satiety and metabolic rate
BEST HOPE
-Sustainable lifestyle changes
–Diet combined with exercise / physical activity
–Ongoing management is required to maintain weight loss
