Eating Behaviour

Leptin:

• HAVEL: hormone that inhibits release of NPY; neurotransmitter that stimulates hunger
• low calorie diet = low leptin = more hunger
• explains difficulty in maintaining weight loss
• MARK: diets have low success rate as they do not address underlying biological or genetic problems such as leptin
• WEIGLE ET AL: weight loss from a low carb., low calorie diet = lower leptin & more hunger
  
• but, if diet is changed to low fat, weight loss = maintained due to no compensatory increase in hunger (i.e. leptin levels stay the same)
  

• TRUBY ET AL: 6 month randomised controlled comparison of 4 commercial diet programmes
• all pps had significant weight loss despite 1 plan being low carb & another low fat - CONTRADICTS LEPTIN EXPLANATION
• something else must play a role (e.g. media as study was filmed)

Operant Conditioning:

• initial, rapid weight loss = motivation - behaviour is reinforced
• when weight loss slows, social support becomes important
• media interest = also motivating in Truby study

Dieters mindset:

• LICHTMAN ET AL: dieters delude themselves - they underestimate their food intake & overestimate their exercise
• OGDEN: difference in psychology of weight loss regainers (stable obese) who tend to attribute weight to biological/genetic factors & weight loss maintainers (no longer obese) who tend to instead attribute it to psychological factors
  

• HERMAN & MACK
• suggests dieting can be successful & lead to weight loss OR unsuccessful, resulting in overeating & weight gain
• KIRKLEY ET AL: 50 women filled in dietary self monitoring forms for 4 days - restrained eaters ate less calories

Boundary Model:

• HERMAN & POLIVY: restrained eaters have a cognitive boundary for eating & once this is crossed, they overeat until they reach physiological satiety which is further from hunger than in an unrestrained eater
• explained in HERMAN & MACK study (preload/test method):
• 45 female students put in 3 conditions: 1) no preload, 2) 1 milkshake & 3) 2 milkshakes
• low restraint pps ate less ice cream after 2 milkshakes whereas high restraint pps ate MORE with 1 or 2 milkshakes => 'what the hell effect' after exceeding cognitive boundary
  

Leptin Hypothesis:

• ignores psychological factors (reductionist)
• no room for free will = deterministic

Psychological Factors:

• ignores biological factors (also reductionist)
• operant conditioning doesn't explain why we might regain weight after diet being so rewarding
  
• idea of mindset & operant conditioning = fairly deterministic

Restraint Theory/Boundary Model:

• doesn't account for any contributing biological factors
• judgement of restrained/unrestrained eaters based on questionnaire = open to social desirability bias