Healthy-Obesity Flashcards
Obese
describes a person who’s very overweight, with a lot of body fat. It is a common problem in the UK where its estimated to affect around 1 in 4 adults and 1 in 5 children. (NHS Website)
Body Mass Index (BMI)
used to measure obesity. A measure of whether you’re healthy for your height.
Biological factors:
Genetic explanation
-Family clusters
The weight of your parents is likely to determine the weight of their children.
If one parent is obese=40% chance child being obese.
Both parents=80% chance.
Parents thin=7% chance.
Same observations are found cross culturally (Maes et al 1997).
BUT parents and children share the same environment.
Biological factors:
Genetic explanation
-Twin studies
Stunkard et al (1990) examines BMI of 93 pairs of identical twins reared apart= found that genetic factors accounted for 66-70% of variance in body weight.
Suggests a strong genetic component in obesity.
But what about other 30%?
Biological factors:
Genetic explanation
-Adoption studies
Stunkard et al (1986): gathered information about 540 adults adoptees and their biological parents and their adoptive parents.
Results= strong relationship between the weight category of the adoptee and of their biological parents. (=suggests major role of genetics).
Biological factors:
Thrifty gene hypothesis
As it’s a global problem-suggests evolutionary.
• An evolutionary explanation=storing fat as an adaptive response.
• Functional to store fat when food is in short supply, however this is inappropriate now as food is abundant.
Neel (1962): “in such an environment, genes that predispose to obesity increase energy stores and provide survival advantages in times of famine.”
• Individuals who were most energy efficient in terms of burning off excess energy and remaining thin would have been less successful.
• Therefore we are now left with those who were best adapted to surviving harsh winters and floods, which resulted in food shortages and famine.
• Now, lots of food and increasingly sedentary lifestyles, these people overeat=obese=health problems.
Ψ The environment no longer needs their thrifty gene.
Strengths of biological explanations
- Drug treatments can be used.
* Useful to know-can educate to prevent.
Limitations of biological explanations
- Gives people an excuse-removing the blame from an individual suggesting that their weight is out of their control.
- Some people more susceptible than others=hard to control.
- Reductionist- increase in obesity within the last 20 years has occurred over too short a period for genetic makeup to have changed substantially.
Cognitive factors:
Cognitive restraint theory
Suggests that people who diet replace physiological hunger sensations with “cognitive restraint”- they put a cognitive limit on what they eat.
BUT this is not enough in eliminate hunger signals and according to cognitive restraint theory, dieting lead to obesity.
Herman and Mack (1975)
Aim: Investigate cognitive restraint theory using Preload/taste test method.
Method:
• Told 45 female students they were participating in a taste test, half we given a high calorie preload and half a low calorie preload.-half the participants of each group were dieters and the other half non-dieters.
Findings:
• Restrained eaters in high calorie preload went on to eat the most.
• Whereas the non-dieters showed compensatory regulatory behaviour and ate less during the taste test after high calorie preload, the dieters consumed more in the taste test if they had the high calorie preload than the low calorie preload.
Evaluation:
+
Approach they used was novel and interesting and finding challenged some of the contemporary ways of thinking about eating behaviour.
Demonstrated trying not to eat could result in overeating.
Took place in controlled lab setting= credibility.
-
Lab=low EV.
Small sample.
Sociocultural:
Physical activity
General decline in physical activity is recent years. Why? Increases in: • Car use • Internet • Mobile phones
Prentice and Jebb (1995)
Aim: investigate the association between reports of car ownership and TV viewing and population changes in obesity.
Results: strong positive correlation between an increase in both car ownership and television viewing and an increase in obesity.
Conclusion:
Low levels of physical activity in Britain and reduced energy needs must have played an important role and, possibly even a dominant role, in the development of obesity.
Evaluation:
+
Used a large population=results generalizable.
Objective measure of activity in the form of car ownership, which is less contaminated by the problems of self-report than other measures used in questionnaires.
Population data of obesity were used rather than using people’s self-report height and weight, which are known to be inaccurate.
Suggests in can easily be controlled through change in lifestyle.
Compliments thrifty gene hypothesis.
-
Correlational not clear whether decreases in activity cause obesity or whether increases in obesity cause decreases in activity. Also possible are not directly related and some unidentified factor may determine both obesity and activity.
May overall individual differences as at population level eg people who are obese and active, people who are thin and inactive.
Doesn’t explain why some active people/good eaters are still ‘fat’ and vice versa.
Relationship between physical activity and excess weight gain
also been observed in Finland with Rissanen et al (1991) following 12,000 adults over a five 5 period. They found that lower levels of activity were a greater risk factor for weight gain than any other baseline measure.
Bullen et al (1964)
Observed adolescent girls on a summer camp and found that during swiiming obsess girls spent less time swimminh and more time floating than their non-obese counter[arts and during tennis, obese girls were inactive 77% of the time compared with 56% of the time in non-obese girls.
Evaluation:
+
Did show clear relationship between activity levels and obesity in female adolescents.
Observation= high EV
-
May be subject to observer bias
Ethics of observation
Young female only sample= low generalizability
Summary sociocultural factors
Summary
• Positive correlation between population decreases in activity and increases in obesity.
• Evidence for obese people exercising less than obese people.
• BUT in inactivity a cause or a consequence for obesity.
While the research is undeniable that a lack of physical activity causes obesity, it is important to take a holistic approach when looking at the development of obesity as biology and cognition both clearly also play a role.
