Success & Failure of Dieting

Explanations for success or failure of dieting

Why do so many females want to lose weight?
It’s estimated at any 1 time 40% of the female population is trying to lose weight, usually by dieting.
If you are obese, losing weight has many health benefits. But many females diet when they have faulty perceptions of their actual body or are simply dissatisfied with their bodies. Ogden (’07) suggests some factors: Media Influence, Family, Ethnicity, Social Class, Peer groups & social learning.

Why doesn’t dieting work?
Some women can lose and maintain weight using diet only. However, most can’t and bizarrely they end up eating more. Boundary model; Normal circumstances- Body weight set point controlled through homeostatic mechanisms, can’t fluctuate too much (PHYSIOLOGICAL BOUNDARY). But in restrained eaters person also has a COGNITIVE lower than PHYSIOLOGICAL. Tested using Preload/taste test. Non-dieters eat until they’re full; physiological. Dieters eat until cognitive reached; if high calorie preload disinhibits eating behaviour so eat until satiety. Ogden ‘what the hell’

Herman and Mack: 3 conditions: 1st group no preload, 2nd group 1 milkshake, 3rd group 2 milkshakes
- 2 & 3 asked to rate quality of the milkshakes then all given 3 flvours of ice cream given 10 mins to rate taste, told eat as much as they want. All pps given questionnaire to assess degree of dieting.
All groups put into subgroups according to dieters and non-dieters. Found non-dieters at less in the 2 milkshakes conditions; understandable as would be fuller. BUT surprisingly dieters ate significantly more in the 1 and 2 milkshakes condition than 0. Also the more they were trying to diet, ...

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Herman&Mack’s preload/taste-test was a lab experiment carried out in controlled conditions, so it had high reliability
Cause\effect can’t be established as other variables such as mood may have showed the correlation
PPs were all females so results cannot be generalised to male population
No account of individual differences- as sample small not all may like ice cream
Element of deception but needed for validity of experiment, debriefed after.
Not unethical; eat as much or as little pps liked
Given course credit for taking part – so not real ‘volunteers’

Overall Evaluation

Boundary model- Combines biological & psychological factors to explain feeding behaviour
Much research lab exp – high reliability as controlled conditions but low ecological validity as dieting in real world more complicated ..........
Doesn’t explain what cognitive/emotional processes lead to ‘what the hell’ effect
Ogden- restrained eaters preoccupied with thoughts of food then try to suppress them. Research shows the more thoughts we suppress the more we think about it. Hence, may overeat as rebound effect of trying to suppress thoughts about food.
Dieting associated with low moods, depression linked to low self esteem and food can be used to raise moods. So increased motivation to eat more, but if they overeat blame themselves and continue to overeat hence the ‘what the hell’ effect.
Like the research discussed- Mann et al found in the real world low calorie diets are ineffective and in long term 1 to 2 thirds gain weight!
‘Yo-Yo dieting’ are repeated dieting attempts actually lead to higher risk of heart disease
Too many extraneous variables for significant conclusions e.g. culture, social class etc

How can dieting work & other treatments?

Powell et al suggest dieting successful if combined with lifestyle changes e.g. PE, group/individual support and self monitoring(diary monitor progress- feel increased control)
Set realistic goals which can actually be maintained and good for health – Powell et al
Psychology/physiology of dieting explains failures of dieting but also helped develop psychological and medical intervention to help weight loss.
Pharmalogical treatments: Treatment of Obesity, significant weight loss but side effects. Never recommended for long term as they don’t deal with psychological aspect and could be dangerous side effects. Orlistat- Stops absorption and processing of fat so it’s excreted Side effects e.g. oily faeces. Sibutramine- acts on brain serotonin pathways which regulate food intake. SE e.g. High BP.
Surgical Treatment effective as stomach factors e.g. ghrelin in eating avoided and appetite reduced. Only used if obesity is life threatening as dangers of surgery and SE e.g. abscesses and lung infections also mortality rate 2-4% : Gastric band- around stomach reducing size hence amount of food eaten to feel full, Gastric Bypass- tube b/w duondeum and stomach again reduce stomach size so only small meals can be eaten.