Obesity & CHD Flashcards
Distribution of fat
- Fat can be subcutaneous (under the skin) or
- visceral (around the organs)
- The greatest concern is that visceral fat can interfere with the functioning of vital organs
- Fat deposits around the middle are associated with visceral fat (i.e., Apple-shaped body)
The World Health Organization: Obesity
Overweight and obesity are defined as abnormal or excessive fat accumulation that may impair health.
Why is it important?
• Increased risk of a broad range of health conditions and
mortality, also poorer psychological wellbeing
• Cancers, stroke, CHD, type II diabetes etc
• Possibly depression, stereotyping and negative attitudes
A problem?
- Associated with cardiovascular disease, diabetes, joint trauma, back pain, cancer, hypertension, and mortality
- Men more likely to be obese, women more likely to be concerned – more research on women
- Link to mortality clearest at extreme levels, but many studies of many types have made link clear – 2002 House of Commons about 7% of all UK deaths attributable to obesity
Psychological problems?
- Focus on body shape – aversiveness to fat, attribution of blame, might promote low self esteem and poor self-image
- Certainly strong stigma common
- Consistently higher rates of depression (often in clinical studies where people are awaiting surgical intervention), but also in general population – lifetime diagnoses of depression, bipolar, panic disorder, agoraphobia (Simon et al., 2006), but not always (Ross, 1994)
What causes obesity? Genetics?
One obese parent > 40% chance of obese child, two obese parents > 80%
• Twin studies - Stunkard et al. (1990) found that 60-70% of variance in body weight was determined by genetics.
• the role of genetic appears to be greater in lighter twins.
• Adoptee Studies – strong relationship between adopted child and biological parents’ weight class (especially mother).
• No relationship with adoptee parents’ weight class.
Metabolic rate: Part 1
• The rate of energy use for necessary biological processes (resting
metabolic rate- RMR) is heritable
•Relationship between metabolic weight gain:
• Researchers studied RMR of Pima Native Americans (80% obesity rate) through breathing over a 40-min period – oxygen consumed and CO2 were measured.
Metabolic rate: Part 2
- After 4 years, the participants who gained weight had the lowest metabolic rates. Similar results in other studies.
- Other research indicates that overweight people have slightly higher metabolic rate, although they might have lower rates prior to their weight gain.
- Higher metabolic rate required to maintain larger body
Appetite control - leptin: Part 1
- A hormone released by the fat cells decreases food intake and increases energy expenditure
- Plays a role in feeling full
- The role of leptin was clarified during experiments with mice:• Following a genetic mutation, leptin was not produced in some mice – these mice did not feel full, and therefore ate excessively.
Appetite control - leptin: Part 2
- Ob gene – some humans absent, do not produce leptin (Farooqi et al., 1999)
- However, injections of leptin are not the answer, as obesity is associated with leptin resistance.
- i.e., large amounts of circulating leptin having no effect
“Obesogenic environment”
- Rapid increase since mid 1970s, something in the environment?
- Food industry, advertising, labelling, availability of energy dense foods
- Sedentary lifestyle, lack of manual labour, transport, computers, tv, urban design, lifts, escalators, etc etc
- Easier to gain weight than to lose it, and easier than ever to gain weight
- A focus on environment warranted?
Physical inactivity
- Approx 20% of men and 10% of women employed in ‘active occupations”
- TV viewing – 1960’s 13 hours per week, 1990’s 26 hours per week, currently similar but also more ‘screen time’
- Yet we complain we are busier than ever!
- Lot of data shows steady (or declining) caloric intake since 1970s paralleled by increase in body fat…
- Activity is implicated, more devices, more sedentary careers, more cars etc
- Calories from what?
Eating
- Exposure, modelling, associative learning, availability, emotions, body (dis)satisfaction, dieting etc…• Food used as reward, when comfort required, modelled by parents
- But, most data show overall decrease in caloric intake since 1970s
- Carbohydrates and fat…• Proponents for each as the key factor, and some research suggesting they interact – a balance?
- As always, it’s complicated
Fats and carbohydrates: appetite regulation: Part 1
- Complex carbohydrates and energy use
- Body uses carbohydates for energy, intake increases utlisation, not so with fat - carbs burned (as needed) and fat stored
- Complex carbohydrates and hunger
- Some argue complex carbohydrates (breads, potatoes, pasta, rice) suppress appetite due to their bulk… evidence mixed
Fats and carbohydrates: appetite regulation: Part 2
- Fat and hunger
- Fat more resistant to appetite suppression
- Complex carbohydrates are better for energy, but not necessarily better overall… fruit, veges, milk, contain simple carbohydrates… so often come in context with substantial nutritional benefit… but also added in large quantities to processed foods
