science of bodyweight lect 3

Question 1

what are the 3 ways to reduce bodyweight

Answer 1

dieting (lifestyle modifications)
drugs
bariatric metabolic surgery

Question 2

what is the historical development of dietary restrictions

Answer 2

dr george cheyne 1708
-reduced bodyweight by taking diet of milk with seeds, bread, mealy roots and fruit
-lost between 16 and 18 stone (102-114kg)
(strings 2019)

Question 3

what are the findings of the WRAP trial

Answer 3

-1 year follow up assessed mean weight changes in groups
-brief intervention = loss of 3kg
-12 week programme = loss of 5kg
-52 week programme = loss of 7kg

Question 4

what do the findings of the WRAP trial suggest

Answer 4

longer the intervention = greater weight loss
-difference between groups still significant after 2 years but NOT after 5 years
-most of weight lost in first year
-there is a problem maintaining weight

Question 5

what does the research into duration of effect of dieting show

Answer 5

Crawford et al
-might yield results in the ST but not LT
-54% gained weight in first 12 months
-26% maintained weight over three years
-5% lost (after 1 year) and maintained weight successfully over the next 2 years

Question 6

what happens when undertaking an energy restricted diet

Answer 6

Mars et al
-looked at leptin and appetite ratings
-44 healthy adult male pp (mean age of 43) (mean BMI = 27.3 = overweight category)
-measured over a 4 day diet (36% energy requirement provided)
-looked at fasting leptin cone and appetite levels

Question 7

what are the findings of Mars’ study into an energy restricted diet

Answer 7

-after 4 days fasting leptin concentration decreases by 39%
-leptin levels are negatively correlated with hunger/desire to eat/total appetite (as leptin decreases, hunger increases)
-suggests leptin has an important role in bodyweight regulation (likely mediated through appetite)
-helps us to understand role of leptin

Question 8

what happens when diet is nutrient targeted

Answer 8

wiegle et al
-looks into protein and weight loss
-19 pp
-2 week weight maintaining diet (15% protein)
-2 week iso-caloric diet (30% protein) (calorie controlled specific to indiv)
-12 week ad libitum (30% protein) (pp eat as many calories as the want)
-measured levels of insulin, ghrelin and leptin

Question 9

what are the findings of wiegle nutrient controlled diet study

Answer 9

-satiety increased on iso caloric diet (less hunger) with no change to leptin
-ad libitum: energy intake decreased, bodyweight decreased by 4.9kg, decreased leptin and ghrelin
-decreased leptin = anorexigenic affect/ appetite suppressing

Question 10

what are the basic drug mechanisms

Answer 10

1.decreasing appetite and caloric intake
2.increasing energy expenditure
3.decreasing fat absoption

Question 11

what is an agonist

Answer 11

binds to receptor and produces an effect within the cell

Question 12

what is an antagonist

Answer 12

binds to same receptor but does not produce response, instead it blocks that receptor from a natural agonist

Question 13

what is an analogue

Answer 13

compound having structure similar to that of another compound but differing from in in respect to a certain component

Question 14

lorcaserin

Answer 14

-serotonin agonist, decreasing caloric intake
-part of anorexigenic pathway
-humans fmri study
show pics e.g doughnuts
when taking drug = decreasing emotion and saliency related to activity or limbic system
decreases activity of parietal and visual cortices in response to highly palatable food

Question 15

phentermine hydrochloric, deithylpropion, benzphetamine, phendimetrazine

Answer 15

-noradrenergic agonists suppress appetite
-humans: mechanism of action not completely understood
-rats: acting on homeostatic related hypothalamus and reward related nucleus accumbens

Question 16

phentermine and topiramate

Answer 16

-combination of these suppresses appetite
-humans: mechanisms poorly understood
-phentermine: enhances release of serotonin, norepinephrine and dopamine
-topiramate: GABA agonist, glutamate antagonist and carbonic anhydrase inhibitor

Question 17

naltrexone and bupropion

Answer 17

-both have weight loss as side effect
-work to increase POMC peptide production, regulate appetite and decrease food intake
-rats: bupropion act on POMC neurons and activates anorexigenic pathway
-humans: fmri showed change in response to food in hypothalamus

Question 18

ciraglutide and semaglutide

Answer 18

-blood glucose regulation
-slows gastric emptying
-increases fullness
-acts on hypothalamus, reduces appetite/hunger etc
-rats: acts on reward system to reduce intake of highly palatable foods
-humans: altered activation in response to images of desirable foods, decreased hunger and increased fullness

Question 19

orlistat

Answer 19

-inhibits gastrointestinal and pancreatic lipases
-reduced fatty acid absorption
-1/3 of fatty acids in foods not absorbed

Question 20

how does bariatric surgery work

Answer 20

weight loss via
-restricting amount of food stomach can hold
-malabsorption of nutrients
(or a combination of both)
(often causes hormonal changes)

Question 21

gastric bypass

Answer 21

Roux- en - Y gastric bypass
- small stomach pouch created
-beginning of small intestine divided and one part brought up to reach new stomach pouch

Question 22

sleeve gastrectomy

Answer 22

-laparoscopic sleeve gastrectomy ‘The sleeve’
-removal of about 80% of stomach
-creates tubular pouch
-effect on gut hormones

Question 23

adjustable gastric band

Answer 23

-small stomach pouch via inflatable band around upper part of stomach
-port allows for filling of band with saline

Question 24

biliopancreatic diversion with duodenum switch

Answer 24

-first part similar to sleeve gastrectomy
-second part involves bypassing of large section of small intestine

Question 25

procedures around the world

Answer 25

-23 countries
-311,441 procedures registered
-61% sleeve gastrectomy procedures

Question 26

success of bariatric metabolic surgery

Answer 26

Sjostrom (swedish obese study)
-all pp lost weight but struggled to maintain it

Question 27

bariatric surgery and ghrelin

Answer 27

-ghrelin decreased
-removal of gastric fundus = main source of ghrelin
-variability due to differential exclusion
-ghrelin changes might underpin post surgery decrease in liking of palatable food, new food dislikes and changes in taste

Question 28

bariatric surgery and leptin

Answer 28

-leptin decreases after surgery = in line with weight loss
-adipose tissue secretes leptin, as volume of adipose tissue decreases so does leptin

Question 29

other hormones and bariatric surgery

Answer 29

-GLP-1, increases after surgery (anorexigenic pathway)
-post prandial levels increase after surgery
-effects seem to by LT

Question 30

variability evidence after bariatric surgery

Answer 30

Hollanda 2015
-looked at people after surgery
-1 year more weight loss, maintained for some but not all

Question 31

effects/co morbidities associated with obesity

Answer 31

-cardio vascular disease (ortega 2016)
-type II diabetes (mokdad 2003)
-some cancers (Font Burgada 2016)

Question 32

who reviewed the relationship between obesity and cog functions by using reaction times

Answer 32

Prickett et al

Question 33

supportive links with bodyweight and cog

Answer 33

-intellectual functioning
-psychomotor performance and speed
-visual construction
-decision making

Question 34

no links between bodyweight and cog

Answer 34

-general cog performance
-time judgement
-working memory
-verbal fluency

Question 35

mixed evidence for bodyweight and cog

Answer 35

-visual memory
-verbal memory
-complex attention
-inhibition

Question 36

weaknesses of studies into bodyweight and cog

Answer 36

-many studies fail to account for cofounds e.g age, education, depression
-many studies do not use exclusion criteria (people included who have cog deficits)
-lack of comparison groups
-publication bias (sig effects published)
-quality of assessment tools varied
-lack of broad assessment of cog domains

Question 37

leptin and cog functions

Answer 37

-leptin associated with impaired cog function
-higher bodyweight = higher adipose tissue = higher leptin = lower cog function
-leptin influences hippocampul dependent learning and memory
-anti depressant properties

Question 38

inflammation

Answer 38

-inflammation related with immune system is associated with obesity
-increase of adipose tissue = cell death = inflammatory marker
-inflammation causes neuronal dysfunction
-associated with subtle cog deficits

Question 39

balter research

Answer 39

-reaction time test for people with high and low BMI for diff ages
-older and high BMI had worst reaction time
-higher reaction time for high BMI due to inflammation

Question 40

can losing weight improve cog fucntion

Answer 40

• yes attention and memory improved
  -veronese: overall there is an improvement in cog function when people lose weight

Question 41

is food addiction a valid concept

Answer 41

fletcher and kenny
-not enough support (fletcher)
-there is enough support (kenny)

Question 42

what are the behavioural and clinical features of food addiction

Answer 42

-addiction from DSM 5 has 11 criteria e.g taking substance in large amounts, craving it, wanting to stop etc

-Yale food addiction scale (Gearhardt et al 2009)
-self report questionnaire
-symptom count: how many of 11 criteria points to food addiction
-limited predictive power
-does not give clear pic about behavioural and clinical signs

-concept of food addiction does not directly map onto DSM 5

Question 43

what is an addictive substance (food addiction)

Answer 43

-many studies on sugar addiction are with animal studies
-not generalisable to humans
-more evidence needed
-no consistent evidence for sugar addiction

Question 44

is there a neural basis for food addiction

Answer 44

-overlapping neural substrates
-dopamine released when drugs taken and when we anticipate or eat food
-sensitisation seen over time (robinson and berridge) leading to increased wanting of food/drugs
-food lacks the motivational intensity of drugs
-reduction of D2 binding in substance addiction and obesity

Question 45

what are the 3 things we need to establish in food addiction

Answer 45

1.behavioural and clinical characteristics
2.the addictive substance
3.neural mechanism