Obesity/Diet Flashcards
Prevalence of obesity
From Health survey for England (HSE) and National child Measurement Programme (NCMP) as official national statistics
2014: 58% womrn, 65% men overweight/obese
26% overall obese
Almost doubled since 1993
2014/2015:
1in5 children in reception overweight/obese
1in3 children in year 6 overweight or obese
WHO definition
Overweight and obesity are defined as abnormal or excessive fat accumulation that may impair health
Measuring Obesity:
BMI
Limitations of using BMI
weight in kg/height in m2
underweight: <18.5 Normal: 18.5-24.9 Overweight: 25-29.9 Obese: >30 Severe (morbid) obesity: >40
Limitations:
- no acknowledged difference in fat and muscle
- No acknowledgement of fat placement
- Doesnt account for ethnic difference - south asians have incr risk of weight related diseases at lower weight
UCL study on self-perception of obesity
Johnson et al 2014
2 surveys 5 years apart (2007+2012)
Results showed very few obese people described themselves as obese
women ~12%
Men <10%
There was awareness that stigmatisation may go with the term obese, so also looked at “very overweight” however still very few identified in this category, even fewer women
Black et al. 2015
parents estimating children’s BMI
Looked at children aged 4-5 and 10-11, asked parents to determine BMI
results showed that 1/3 parents underestimated BMI
NB:Overweight children at increased risk of premature mortality and obesity-related disease in adulthood
Jackson et al 2015
adolescents perceptions of their own weight
Looked at adolescents aged 13-15 from annual health survey for england between 2005&2012
asked if they thought they were too light/heavy/just right and also weighed & measured
Results: very few normal weight teens thought they were overweight but overweight teens didnt aknowledge - 39% of overweight teens said they were just right
Measuring Obesity:
Waist Circumference
Men: overweight = >37in
obese >40in
Women: >32in
obese:>35in
(ethinic specific values have been defined)
Measuring Obesity:
Waist to height ratio
Ashwell et al 2012
Waist should be <1/2 height
meta-analysis of 31 studies, over 30,000 people in different ethnic groups showed this was better than WC & BMI for detecting cardiometabolic risk factors
Measuring Obesity:
% body fat - calipers
Bodystat + Tanita
inches of fat in area /height x 27 = body fat %
1st height, weight, age & gender is noted
A small electrical current is circulated, resistance to the current by fat and muscle is measured
resistance depends on fat and muscle as muscle holds more water than fat so current moves through the body with less resistance
Hydrostatic body fat testing
BodPod
considered to be gold standard
expensive & uncomfortable
person must empty their lungs as much as possible, then put in tub and must hold their breath
BodPod:
Also considered gold standard
expensive
equally accurate to hydrostatic
uses air displacement plethymography to detect small changes between fat and lean body mass ie bone muscle organs
person sits in pod for 2-3 mins and volume of air displaced by the body is measured and body fat % calculated
Health Consequences of Obesity
European investigation into cancer & nutrition
Studied relative risk of death among men and women according to BMI & WC, adjusted for age, smoking status, educational level, alcohol consumption, physical activity & height
showed famous J shaped association - normal BMI/WC hits the line of relative risk, then higher rate is found in those with high/low body fat
showed that WC & BMI useful for predicting death
CVD & obesity
Smolina et al 2002
CVD = leading cause of death worldwide
WHO: 30% of worldwide deaths every year
mortality from CVD in the UK has been falling since 1970s - DR from MI have halved since 2002
Smolina et al believe drop due to:
decr smoking
incr hospital treatment
incr management of BP & choelsterol
massive cost to UK
To NHS- £8.7bill
to economy - £19bill
Diabetes & CVD
complications
micro/macrovascular
Obesity is leading caus of T2D
diabetes is incr in prevalence globally & in UK
382million adults have T2D
around 45% sufferers dont know they have it
10% of NHS budget
Complications:
- Chronic hyperglycaemia caused by diabetes linked with long-term damage, dysfunction & failure of various organs
- Harmful effects divided into microvascular & macrovascular complications
microvascular:
retinopathy- damage to the eye, biggest cause of blindness
nephropathy-damage to kidneys, can lead to kidney failure
neuropathy - can lead to foot ulcers, biggest cause of amputation
macrovascular:
Stroke
CHD
Peripheral vascular disease
Obesity & cancer
Link beteen weight and cancer is firmly established (Guh 2009)
meta-analysis of 89 studies:
-overweight & obesity was assoc with incr risk of Breast, colorectal, endometrial, kidney & ovarian Ca
Other consequences of obesity
asthma
gallbladder disease
osteoarthritis
chronic back pain
Adipose tissue as an endocrine organ
Most important to take intra-abdominal fat into account when considering obesity
white adipose tissue is highly complex: composed of various cell types that interact dynamically with each other through secretory factors called adipoteins including: hormones cytokines chemokines
abdominal fat releases adipoteins into the circulation
adipoteins are associated with: IR dyslipidoemia incr LDL cholesterol Triglycerides decr HDL cholesterol incr BP
Diet:
foods linked with ill health
saturated trans fat
salt
sugar
red meat
Diet:
foods linked to good health
strong assoc for red CVD: antioxidants vit C vegetables Nuts Mediterranean diet
mod evidence for protective effect: fruit fish wholegrains fibre
Diet & CVD
high sodium diet increases risk of hypertension which is a CVD risk factor
strong evidence that trans fats contribute to CVD through atherosclerosis
Emotional consequences of obesity
YOUNG
body dissatisfaction
slightly lower self-esteem in community samples
higher rates of depression in clinical populations
discrimination & social exclusion - incr bullying & teasing at school, decr college attendance
-teachers rated ability of obese girls lower
Emotional consequences of obesity
ADULT
body dissatisfaction
higher rates of depression with higher grade of obesity
less likely to get married
employment: employers less willing to hire obese people, obese people earn less, less likely to get a promotion
Fat Shaming
Jackson et al 2014 - 2994 people
<1% of normal weight people reported weight discrimination compared to 36% of morbidly obese people
those who reported weight discrimination gained an average of 0.95kg iver the 4 year stufy period
what causes obesity?
GENETICS
two ways to study genetic link to obesity: quantitave i.e. twin studies or molecular (GWAS)
Twin studies: modelled that weight is heritable
GWAS: Found 31 common genetic variants identified as indices for adiposity
identifying SNPs that are related to body weight
but only account for <3% of variation in BMI of both adults & children ==> missing heritability problem
what causes obesity?
OBESOGENIC ENVIRONMENT
the environment we live in makes obesity easy: food environment: -portion sizes -cost -availability -high fat -low fibre (therefore food not filling) -food advertising
Activity environment:
- high cost of activity (gym membership)
- labour saving devices e.g. dishwasher
- sedentary travel (tube>cycle)
- enjoyable sedentary past times e.g. netflix
- high ambient temperature
