Obesity I Flashcards
What is obesity?
*The body utilises fat cells for long-term energy storage *We have 2 types of fat cell *Brown fat cells (BAT) are used to generate heat and are located either side of the spinal column (shoulders) *BAT are rich in mitochondria (hence high energy use) and are not directly implicated in obesity *BAT cells contain 30-50% fat *BAT constitute 5% of the body mass of babies to generate heat *The distinction between the 2 types may not be absolute
What are 4 functions of white fat cells?
–They insulate the body
–They cushion the internal organs
–They form the bodies long-term energy store
*Each white fat cell is 85% fat
*This is stored in a single large vacuole
*It is not currently known whether obesity is the result of the progressive enlargement of a set number of white fat cells or enlargement plus the addition of new white fat cells
–White fat cells serve an important endocrine function
*Leptin
*Resistin (producing insulin resistance in a variety of cell types)
*Fasting-inducing Adipose Factor (akin to Leptin in action)
*The full variety of this endocrine role is not as yet fully elucidated
How do we gain white fat cells?
*Around 20% of an average weight woman and around 15% of an average weight man is composed of white fat cells
*This represents roughly 1 months store of energy
*White fat cells are distributed in different ways in men and women
*Women more on hips/thighs and men more on the waist
*Subcutaneously and around organs in both
*When we ingest more energy than we use we are in positive energy balance
*It is under these conditions that we start to turn this excess energy into fat which is stored in the white fat cells
*It is this process which can ultimately result in obesity
How do we measure obesity?
*The aim of all forms of obesity measurement is to estimate the proportion of a person’s body which is made of fat (i.e., white fat cells)
*The most frequently used measure is the Body Mass Index (BMI) or Quetelet’s index.
*To calculate your BMI you divide your weight in Kilograms by the square of your height in Metres
What do different BMIs mean in adults?
*BMI’s below 18.5 are in the underweight range
*BMI’sof 18.5-24.9 are in the normal range
*BMI’sof 25.0-29.9 are in the overweight range
*BMI’s above 30 are in the obese range
–Moderate obesity 30.0-34.9
–Severe obesity 35.0-39.9
–Very severe obesity 40.0+ (or Morbid obesity)
*There is someargument about where cut-offs fall
What are 4 pros and 4 cons of BMI?
*For
–Easy to use
–Can be measured remotely
–Accurate
–Correlates with adiposity (r = 0.4 to 0.9)
*Against
–Takes no account of fat distribution (abdominal vs. other)
–Takes no account of variation in muscle mass (e.g., many professional athletes have BMIs in 25-32 range)
–Influenced by age
–Influenced by trunk to leg length
What are other measures of obesity (4)?
*Skin fold thickness (Calipers)
–Stomach and top of arm/leg
–Does not provide measure of general adiposity
–Difficulty of definition
*Waist circumference
–Around stomach (or waist to hip ratio)
–Good for estimating a separate risk factor for heart disease and stroke
*Excess risk occurs in men with waists 94cm+ and in women with waists 80cm+
–Does not provide measure of general adiposity
–Difficulty of definition, especially in the obese
*Bioelectrical impedance
–Indirectly estimates % body fat by measuring the resistance to flow of electricity through the body
–Very sensitive to hydration status of body
–Only provides a rough overall measure of body fat
*Other measures
–Ultrasound, Chemical [metabolic rate], Computerised Tomography/MRI
What is the prevalence of obesity?
*There is a consensus that we are in the midst of an obesity epidemic
–This is affecting men and women, (and boys and girls), to a similar extent, which is why most of the statistics to come are not divided by gender
What is the obesity prevalence data in the USA?
*The CDC (Centre for Disease Control) provides the worlds most comprehensive set of data on body weight
*These data come from the Behavioral Risk Factor Surveillance System (BRFS) which is a telephone interview conducted with a representative sample of Americans in all states every year
*Studies consistently show that telephone surveys systematically underestimate levels of obesity and overweight (by around 5%) so these are conservative estimates
*This view is supported by the National Health and Nutrition Examination Survey (NHANES) which actually measures people and indicates broadly similar results
Which states have the most obesity?
The states with the most obesity are the poorest states and the states with the most african americans (clear link between socioeconomic status and ethnicity with obesity)
Clear relationship between SES and obesity, more poor = more chance of being obese, highest rates of obesity are found in african americans and latinos bc socioeconomic status and lower levels of education are often tied to ethnicity, low SES gives less access to healthy food (cost) and lack of time (work a lot) and hard to find safe place to exercise, ppl who are poorer have a harder time to live a healthy life, with age obesity increases (gain weight with age) but theres a drop from 64-67 yrs bc obese ppl die younger
What is the prevalence of child and adolescent obesity in the US?
Obesity levels have increased across all ages
What is the prevalence of obesity in the OECD?
Theres a general trend of weight gain across all wealthy countries but not all countries have the same rates of increase, anglo countries increase faster bc of the economic policies (ex. funding of education impacts how much children can exercise)
What is the prevalence of obesity in Australia?
Regional areas of Au are much poorer so have the highest rates of obesity vs cities that are richer so less obese
What is the prevalence of childhood obesity in Australia?
Poorer children are much more likely to be obese
Theres a progressive increase in obesity in kids
What are the health care costs of obesity?
*In Australia estimates suggest that direct health costs from obesity are 10.7 Billion Aus$ per year
*Normal weight direct health costs per year per person = $1472
*Obese direct health costs per year per person = $2788
–In addition, indirect government costs exceed 10 Billion Aus$ for obesity
*In the US direct health care costs for the obese have risen from 52 Billion US$ in 1995 to 178 Billion US$ in 2012 (current estimate, 210 Billion US$)
–Amongst children/adolescents in the US, obesity-related direct health care costs tripled between 1980 and 1998
–Amongst US adults, for cardiovascular disease alone, 17% of all direct medical costs were related to overweight and obesity
