Why do we gain weight?- Lecture 3 Flashcards
NHS (2016)
Obesity rates
62% of adults in UK are overweight or obese
Most at risk
Dieters
Students
Low SES indiv.
Shift workers
Dieters and weight gain
-physiological explanation
-dieting is period of starvation so increases fat storage and food cravings
-Reductions in leptin (hormone produced by fat that inhibits hunger) and insulin
-Increase of ghrelin (associated with increased hunger)
Increased food salience and desire to binge eat
Dieters and weight gain
-psychological explanation
- disconnect with internal signals of hunger and fullness
- stop listening to internal bodily signals likely to rely more on external cues
- relying on external cues in an obesogenic environment can lead to excess food intake
Shift workers and weight gain evidence…
Sun et al. (2017)- meta analysis- shift workers 29% more likely to be obese
Shift workers and weight gain
-Physiological explanation
FAT ABSORPTION
- Disruption of circadian rhythm may influence digestion
- Protein NFIL3 in gut during day is disrupted and can malfunction
- when mice sleep in day less NFIL3 produced so gain weight
METABOLISM
- circadian rhythm also influence metabolic rate
- shift patterns have slower metabolisms (around 8% less) – (Buxton et al., 2018)
- Insulin levels also drop- lead to cravings for sweet energy dense products
Shift workers and weight gain
-Psychological explanation
Tend to increase snack food consumption (Gifkin et al., 2018)- often only food available
- Increased evidence of depression & stress (Driesen et al., 2010)
- Greater levels of emotional eating and other bad coping strategies- e.g. smoking, alcohol abuse, reduced exercise
Low SES and weight gain
In past- social disadvantage used to be associated with undernourishment- swapped around in 1970s (Ban et al., 2018)
TYPE OF FOOD AVAILABLE
- Freedman & Bell (2009)- due to food outlets in certain areas- density of fast food outlets is higher in deprived areas
- evidence linking food outlets to obesity is correlational and weak (Cobb et al., 2015)
Wansink, Painter & North (2005)
Self Filling Bowls- People use the bowl as cue for how much to eat
-73% more eaten in one condition but felt equally
-Fullness determined by how much people ‘believed’ they had eaten
Findings have been replicated (Brunstrom et al., 2012)
EXTERNAL CUES POWERFUL
Low SES and the Insurance Hypothesis
Physiological Explanation
When we think availability of food is not certain- most species seek to store resources (Nettle, 2017)
->humans respond in similar manner - Nettle et al. (2018); Sim et al. (2018)
Nettle (2017) (Insurance Hypothesis)
suggests that because females can become infertile when undernourished, they are more likely to store food during times of uncertainty
Insurance Hypothesis Evidence:
Nettle (2018) study
Sim et al (2018) study
-food insecure individuals ate more in a taste test
And moderated by childhood experience of food insecurity
-manipulated how deprived people felt by asking them to imagine scenarios where they were mistreated= Relative deprivation predicted intake
Limitations of Insurance Hypothesis Evidence…
- Correlational
- Not tested in actual food insecure populations (e.g. food bank visitors)
- Rationers didn’t have higher rates of obesity
Social disadvantage and coping mechanisms
Hemmingsson (2014) model posits that psychological and emotional distress is a fundamental link between socioeconomic disadvantage and weight gain- how we cope with these stresses such as emotional eating.
-BUT only theoretical model…
Spinosa et al (2018)
Tested out Hemmingssons model ->Psychological distress and subsequent emotional eating represent a serial pathway that links lower SES with obesity
Freshman 15
In first year of Uni- av. weight gain of 15 pounds (1 stone)
Due to:
1.Change in eating habits- meals higher in calories, uncertainty about nutrition
2.Late night eating- less governed body clock
3.Stress/emotional eating- lots of work
4.Drinking- social norms at uni
5.Snack eating- whats available
What makes an Obesogenic Environment?
Variety
Distraction
Portion Size
Variety
Obesogenic Environment
Variety stimulates appetite
Even different forms of the same flavour
Sweet and savoury most dramatic as at either ends of flavour
Even in ‘fake’ variety (Kahn & Wansink, 2004) i.e. smarties in diff colours
Variety
Obesogenic Environment
Variety stimulates appetite
Even different forms of the same flavour
Sweet and savoury most dramatic as at either ends of flavour
Even in ‘fake’ variety (Kahn & Wansink, 2004) i.e. smarties in diff colours
Surrounded by highly palatable foods that are cheaper than nutririonally rich foods
Why does variety make us eat more?
Sensory specific satiety- become satiated when eating the same food
New sensory properties of food leads to increased appetite
Bodies are designed for scarcity but operate in times of plenty
Psychological explanation behind variety effects
Using heuristics
Decide how filling a food is by weight (Spence et al, 2014) or by volume (Keenan et al., 2015)
Distraction
Obesogenic environment
Performing multiple tasks (phone, watching tv) whilst eating, increases consumption (Oldham- Cooper et al., 2011).
IMPORTANCE OF MEMORY
Bottom-less bowls (Wansink, painter & North, 2005)
Could be that we require memory to code how much we’ve eaten
Brunstrom et al. (2012)
Amnesic patients find difficult to register fullness as their episodic memory is impaired- Participants who thought they had consumed the larger 500-ml portion reported significantly less hunger- perceived hunger over actual
Portion size
Obesogenic environment
Applies to all types of foods and drinks, meals and affects almost everyone- bar very young
children
