science of body weight week 2 Flashcards
obesogenic environment
an environment that promotes gaining weight and one that is not conducive to weight loss.
explain the key milestones/ changes in the environment
-advent of agriculture
- rise of slave trade ( availability of sugar)
- rising rates of obesity in the last 50 years
what are 5features of an obesogenic environment
- energy dense foods
- highly palatable food
- large portion size
- abundance (opportunities)
- food variety
how does ultra-processed foods drive excess intake
Rolls (2020) : easy to get hands on = low cost and convinced
energy density : palatability (preserves test good, sugar) and eating rate (easy to get more energy) increase.
what are the issue with research into ultra processed food
- correlation does not mean causation
- epidemiology is not experimental
- BMI is problematic so how do we know we’re measuring obesity
- issues with first language
processed vs ultra- processed foods
processed : at home
ultra- processed : more industrial
multi- component food
are those that involve more than one food class being brought together usually via processing of some kind, in order to make a single product
How does multi component food increase food intake
sensory-specific satiety
food variety
portion size selection
food intake increase
habituation
- most basic form of learning
- diminishing response to a repeated stimulus
- most know in terms of smell
- also applies to taste and eating
Eptien et al (2009) study for habituation
salivation for subject who received lemon or lime juice as the habituating stimulus in trails 1-10
other juice as the dishabituating stimulus in trail 11
presentation of the habituating stimulus in trail 12
hetherington et al (2006) study
used the principle of habituation but with real food
rated pleasantness is preserved in congruent and incongruent condition compared to same condition.
Higher overall consumption in congruent and incongruent conditions compared to control and same condition.
sensory complexity
perception of multiple sensations with a single mouthful of a food/drink as well as across an eating and drinking experience as a whole/
optimal arousal theory
dember and earl (1957) : too complex (may not like to begin with) , as our liking goes up, food that is below that level will create boredom.
gene x environment interaction
different effect of an environment exposures on disease risk in persons with different genotype.
Whats an example of G X E
- pima people are native Americans living in two areas : Glia river and Sierra Madre mountains
- both DNA test - genetic similarity
- high prevalence of type 2 diabetes in population of Pima people living in USA
how do genes play a role in fat
- genes are instructions for cells to produce protein
- proteins perform particular jobs in body
- a mutation or deletion in the DNA - knock - on effect to the proteins and job it could perform
explain the role of leptin
- hormone (protein)
- codded by the ob gene on chromosome 7
- produced by adipose tissue
- can cross the BBB to reach hypothalamus
- influence appetite and energy expenditure
What are the findings by leptin?
1949 : mutation on the ob/ob gene in mice, cannot produce leptin, ate excessively, gained weight.Leptin administration = reversal.
1999: leptin should =ivly correlate with body fat, case reports for children with congenial leptin, result in hyperphagia and sever obesity
leptin therapy led to weight decrease
how does leptin work in humans
- binds to receptors in brain and peripheral tissues
- anorexigenic ( Appetite- diminishing ) or orexigenic (appetite stimulating)
- interacts with mesolimbic dopamine system (motivation and reward for feeding)
why do obese people have high leptin levels?
- leptin resistance
- anorexic effect of leptin is reduced
- decrease in leptin across BBB
- defect in intracellular signalling via leptin receptor.
why is leptin not a good explanation for obesity
- mutation for low and high levels of leptin is rare.
5-6%
polygenic risk scores
- meta analysis of genetic studies concered with BMI
- 97 BMI associated SNPs
how do the 97 found genes effect bodyweight
- 5024 PPs
- 90/97 loci use to calculate polygenic risk score
- appetite traits measured by questionnaire (uncontrolled and emotional eating)
what is ghrelin
hunger hormone
