Diet, Obesity and Healthy Related Outcomes Flashcards
How do we measure BMI and what are the cut offs?
weight (kg)/ height (m^2)
Underweight - <18.5 Normal - 18.5-24.9 Overweight - 25-29.9 Obese - 30 and up Severe 'morbidly' obese 40 and up
What are the latest figures of overweight and obesity for men and women?
Latest figures - 2018
~7 out of 10 men are overweight or obese (67%)
More than 4 in 10 men are obese (26%)
2% of men are morbidly obese
6 in 10 women are overweight or obese (60%)
~ 3 in 10 women are obese (29%)
4% of women are morbidly obese
What are some problems with BMI?
- Famously fails to distinguish between fat and muscle- tall man at 6’2” estimated BMI over more than 30
- BMI is a unreliable indicator of actual fat- It fails to account for WHERE fat is located on the body
- BMI does not apply equally to people of all ethnicities- Asians have higher weight-related disease related risks- possible explanation is body fat. South Asians higher levels of body fat. Blacks have lower levers of body fat and higher lean muscle mass lower risk of obesity-related disease. International debate whether cut points for overweight and obesity should be lower cutoffs. China and Japan define overweight as a BMI of 24 or higher and obesity a BMI of 28 or higher; in India, overweight is defined as a BMI of 23 or higher, and obesity, a BMI of 27 or higher
How do we define overweight and obesity using waist circumference?
MEN:
Overweight: WC > 37 inches (94 cm)
Obese: WC > 40 inches (102 cm)
WOMEN:
Overweight: WC >32 inches (80cm)
Obese: WC > 35 inches (88cm)
Describe trends in waist circumference since 1993.
There has been an increase in mean waist circumference among both men and women since 1993.
There are well documented links between high levels of central adiposity in adults, as measured by waist circumference, waist-to-height or waist-to-hip ratio and risk of obesity-related conditions including type 2 diabetes, hypertension and heart disease. These links remain even once BMI is adjusted for, demonstrating that measures of central adiposity are independent predictors of future obesity-related ill health.
What are health consequences of obesity for men and women?
Male deaths (2018) 1. Heart disease 2. Dementia 3. Lung cancer 4. Chronic lower respiratory disease 5. Cerebrovascular disease Influenza and pneumonia
Female deaths (2018)
- Dementia
- Heart disease
- Cerebrovascular disease
- Chronic lower respiratory disease
- Influenza and pneumonia
Expand on cardiovascular disease as a health consequence of obesity.
Umbrella term for a range of diseases
Heart disease and stroke are the leading causes of death worldwide
Confirmed link between obesity and cardiovascular disease
Mortality rates from heart disease and stroke have been falling over the past decades
Cost to NHS over 9 billion yearly
Expand on diabetes as a health consequence of obesity.
Huge increase in the prevalence of diabetes
Type 2 diabetes accounts for the majority of cases
Obesity is the main risk factor for type 2 diabetes
One of the leading causes of death worldwide (4th)
Undiagnosed diabetes is a cause for concern
Expand on cancer as a health consequence of obesity.
Link between weight and cancer is firmly established
2nd biggest preventable cause of cancer
Meta-analysis 89 studies on overweight and obesity
Increased risk of 13 cancers
2 of the most common types– breast & bowel cancer
3 of the hardest to treat – pancreatic, oesophageal & gallbladder cancers
Expand on dementia as a health consequence of obesity.
Emerging evidence in this area
2020 study of over 6000 adults from the English Longitudinal Study of Ageing with 11-year follow-up
Obesity linked with a 31% increased risk of dementia than those with BMI in normal range
Women with abdominal obesity (based on waist circumference) had a 39% increased risk of dementia
No association with waist circumference in men
What are the pathways linking obesity and health?
Direct pathway
Obesity has a direct impact on our physiology
Indirect pathway
Obesity associated with poor health behaviour which in turn impacts health
Expand on the direct pathway.
see ppt slide 25
Expand on the indirect pathway with sleep and obesity
Sleep Short sleep (< 6hours per night) & poor sleep quality increases the risk of obesity
Sleep and metabolic change
Decreased glucose tolerance & decreased insulin sensitivity
Increased evening concentrations of cortisol
Increased levels of ghrelin & decreased levels of leptin
Ghrelin increases hunger signalling
Leptin reduces hunger signalling
Expand on the indirect pathway with diet and CVD.
STRONG EVIDENCE
High-sodium diet increases risk of hypertension
Vegetables, nuts & Mediterranean diet (RCT) are protective
High consumption of trans fats causally contributes to atherosclerosis
MODERATE EVIDENCE
Consumption of fruits, fish, whole grains, fibre and alcohol
WEAK EVIDENCE
Consumption of saturated fat and atherosclerosis
But saturated fats linked with bad cholesterol. Red meat often high in salt!
“Evidence for most nutrients or foods too modest to be conclusive”
Expand on the indirect pathway with diet and Type 2 diabetes.
“Sugar may be linked to type 2 diabetes by making a significant contribution to becoming overweight…sugar alone in your diet is not enough. Weight is determined by total energy intake”.
Diabetes UK
“The myth that sugar causes diabetes is commonly accepted…one of the biggest risk factors for type 2 diabetes is beingoverweight, and a diet high in calories from any source contributes to weight gain”.
American Diabetes Association
Sugary drinks have been linked to 30% increase risk of diabetes
Effect remains even when taking BMI into account (26% adjusting for BMI)
Expand on the indirect pathway with diet and cancer.
Early evidence
Estimated 32- 35% of cancer was avoidable by diet change
But few specific food items have been convincingly linked to cancer
EPIC cohort (EU)
Fruit & vegetables reduce mouth, larynx, oesophagus, lung & bowel cancer risk
No effect on lymphoma, breast, prostate or ovarian cancers
NIH-AARP study (US)
Fruit and vegetable consumption and reduced risk of head and neck cancers
Strong link between red meat and colorectal cancer
Red meat consumption also linked with oesophagus, liver, kidney, and prostate cancers
What are the emotional consequences of obesity in young people and adults?
YOUNG PEOPLE
- Body dissatisfaction
- Slightly lower self-esteem in community samples
- No consistent evidence of higher rates of depression in community samples
- Higher rates of depression in clinical populations
ADULTS
Body dissatisfaction
No consistent differences in self-esteem
Higher rates of depression at the higher grades of obesity
Higher rates of depression in clinical populations
What are the social consequences of obesity?
Educational access
- Lower college attendance
- Lower teacher ratings of ability for obese girls
- Bullying and teasing at school
Marriage and social position
- Less likely to get married
- Downward socioeconomic status trajectory for obese women
Employment
- Employers less willing to take obese people as employees
- Obese employees earn less and are less likely to get a promotion
Social stereotyping
- Unattractive
- Weak-willed
Discrimination
- Out of 2,944 participants less than 5% reported weight discrimination
<1% of ‘normal weight’ reported discrimination
36% of ‘morbidly obese’ individuals reported discrimination
- Weight discrimination associated with 0.95kg weight gain over 4 year follow-up
What is the annual probability of achieving normal weight?
Annual probability of achieving normal weight (n=278, 982):
Obese man: 1 in 210
Obese woman: 1 in 124
Morbidly obese man: 1 in 1290
Morbidly obese woman: 1 in 677
Expand on lifestyle interventions as a treatment for obesity.
Multi-factorial interventions that are tailored according to patient needs and risk factor status
Promoting healthy habits, dietary counselling, exercise training, and behavioural change targets
Meta-analytic evidence:
Analysis of 17 interventions that had a minimum observation period of 1 year
Lifestyle interventions resulted in significant reductions in weight compared with standard care
On average participants lose about 3.5 kg which is maintained for 3 years
Expand on behavioural therapy as a treatment for obesity.
Nutrition and exercise advice
e.g. Easy nutritional swaps e.g. Beeken top 10 tips
Functional analysis of behaviour Self-monitoring of eating and activity Evaluation of positive and negative cognitions Stimulus control in relation to food and activity choices Self-reinforcement of behaviour change Cognitive restructuring Reward good behaviour Relapse prevention
Expand on functional analysis of behaviour and behaviour chain
Functional analysis of behaviour:
- Classical conditioning is central
- 2 stimuli repeatedly paired will become linked
- Eating cookies whilst watching TV –> turning on TV triggers craving for cookies
- Identify and distinguish cues
Behaviour chain:
- One behaviour, linked to another, can contribute to an overeating episode.
- What appears to be an unexpected dietary lapse can be traced to a whole series of small decisions and behaviours.
- The behaviour chain also reveals where the individual can intervene in the future to prevent unwanted eating. Thus, the individual might avoid bringing cookies into the house or at least store them out of sight to reduce impulse eating.
Expand on self monitoring as a behavioural therapy treatment option for obesity,
Most important component of behavioural treatment
People can underestimate calorie intake by 40-50% per day
Detailed records of: Food intake Physical activity Weight Mood (positive and negative)
Reveals patterns such as calories from soft drinks
Monitors internal triggers (e.g. mood modification & “what the hell effect’)
Targets for intervention in the behaviour chain
Expand on cognitive restructuring.
Cognitive restructuring
Modify thoughts that undermine weight loss
The impossibility of weight loss – previous failed attempts
Unrealistic eating and weight loss goals
Self-criticism regarding over eating or weight gain
“I’ve blown my diet so I might as well eat what ever I want”
vs
“I’ve over eaten today, but only by about 400 kcals. If I stop now, I can easily make up the difference by cutting back over the next couple of days”
Can help people feel more positive about weight loss
Disappointment -> abandonment of healthy behaviours
Focus on health rather than appearance aspects of weight loss
Improve body image -> help with acceptance of modest weight loss
How effective is behavioural therapy and does the review of studies from 1996-2002 say?
Effectiveness:
- Favourable results based on WHO criteria
- 5-10% reduction in initial weight
- Dose response relationship between weight loss and treatment duration
Review of studies 1996-2002:
- Group behavioural approach mean weight loss of 10.7kg (~10% of initial weight)
- 30 weeks of treatment
- 80% of patients who begin treatment complete it
Give an example of a pharmacological treatment of obesity.
ORLISTAT:
Reduced weight by 2.9kg on average (2.5-3.2 kg)
Reduced incidence of diabetes
lowered LDL cholesterol and blood pressure
Improved glycaemic control in those with diabetes
But attrition rates 30-40% on average
Expand on the surgical treatment options for obesity and give their mean % weight loss.
Vertical banding - 47.5 Gastric bypass - 61.6 Gastroplasty - 68.2 Duodenal switch - 70.1 Overall: 61.2%
What are the areas of interest when discussing causes of obesity?
- Genetics
- Obesogenic environment
- Psychology of eating behaviour
Expand on genetics as a cause of obesity.
And analyses using data from the TEDS twins at age 10 support the observation that weight is heritable. The bar graph shows the monozygotic twin pair correlation in blue and the dizygotic twin pair correlation in red for BMI- STANDARD DEVIATION SCORE (SDS) on the left, and waist-SDS on the right. As you can see, the MZ correlation is far higher than the DZ correlation, indicating a substantial genetic contribution to these two indices of adiposity.
When modelled formally, heritability to be high at 77% for BMI-SDS and 76% for waist circumference
Expand on the obesogenic environment as a cause of obesity.
FOOD ENVIRONMENT:
- Availability
- Cost –> unhealthy food cheaper
- Variety
- Portion -> sizes increasing over time
- High energy density (kcal/g)
- Low fibre (not filling)
- Food advertising/labelling
ACTIVITY ENVIRONMENT:
- Activity environment
- High cost of activity
- Labour saving devices
- Sedentary travel
- Enjoyable sedentary pastimes
- High ambient temperatures
Expand on psychology and eating behaviour as a cause of obesity.
Basis for eating
- Hunger is biological survival mechanism
- Born with innate food preferences (sweet rather than bitter foods)
- But there are many other reasons for eating other than biological need…
Psychological models of eating behaviour
Developmental model
Cognitive model
Weight concern and body dissatisfaction
Expand on the developmental model of eating behaviour.
Emphasis on learning
Exposure
People show neophobia but this reduces after exposure
Social learning
Importance of modelling and observation
Parental feeding styles and practices are important!
Association
Food as the reward
Food and control- overt & covert differ
Expand on the cognitive model.
- Emphasis on beliefs and attitudes
- Frameworks for explaining, predicting and changing behaviour e.g. Theory of planned behaviour
see ppt for diagram
In the field of eating behaviour research has suggested that intentions are not particularly good predictors of behaviour per se. So this has driven research looking at the intention-behaviour gap
As intentions are not that good as predictors they have looked at cognitive predictors (i.e. attitude, subjective norms, and perceived behavioural control) of eating behaviour
Attitudes has been found to be a fat intake, salt use, eating in fast food restaurants, low-fat milk, f&v intake.
Attitudes centred around positive vs negative attitudes but also ambivalence ie. presence of both positive and negative attitudes simultaneously e.g. tasty vs fattening
Perceived behaviour control associated with eating behaviour in relation to weight loss and healthy eating
Social norms have NOT been shown to predict eating behaviour
What are some problems of the cognitive model?
- Components of model chosen by the researcher based on existing questionnaires important cognitions may be missed
- Ignore meaning of food and body size
- Assumes behaviour is rational ignores the role of affect e.g. emotions like guilt, fear of weigh grain, guilt at overeating
- Ability to predict behaviour is poor- large amount of unexplained variance
What are some problems of the developmental model?
- most of the research has taken place in a lab- generalise to naturalistic settings?
- Food has more diverse meanings than reward and control- more on this later
- Ignores meaning of weight, body satisfaction, ideas of attractiveness success
