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Roux-en-Y bypass - small gastric pouch (15-30mL) on the lesser gastric curvature which is completely divided from the gastric remnant and then anastomoses to the jejunum, get the stomach secretions still


Complication with the RYGB

30 days after the surgery - 4% of patients - bleeding, perforation or leakage - immediate surgical re-intervention


What does RYGB treat? - 3

Not some of the aetiological factors of morbid obesity e.g. obesogenic environment
20-30% long term over 2 years of weight loss and maintenance, >50% of excess body weight
Improvement/remission of many obesity related comorbidities (hypertension, T2D, mellitus, obstructive sleep apnoea and musculoskeletal pain) - 40% of T2D go into remission within days/weeks


What causes the reduced kcal intake after RYGB?

Significantly smaller meal sizes = reduced caloric content


What’s a dominant contributing factor of reduced caloric intake.

Enhanced satiety


Calorie count for post RYGB

Dramatic decrease - 600-700kcal in the first month, then rise to 1000-1800 during the first year.


Changes in behaviour associated with eating after RYGB?

Reported in 1970s using structured interviews that suggested they reached satiety more quickly - common reason of lack of desire for food.


RYGB and endogenous gut hormone responses

Elevated responses for Glucagon like peptide 1, peptide YY respond to mixed meals/oral glucose - may remain high for more than a decade


Why do we think its more than GLP 1 that works after RYGN

Because enhanced GLP 1 signaling is not sufficient to reduce body weight so there should be multiple gut hormone that mediate the increased satiation


Ghrelin and RYGB

Ghrelin deficiency b/c it usually increases after diet induced weight loss


RYGN and neural responses - 2

Reduce hedonic behaviour associated with eating highly palatable and calorie dense foods compared to patients who ha
Selective decrease of reward value of a sweet and fat tastant, but not veggies.


GYFB and total plasma build acids

Pournaras et al - elevated - partly responsible for anorexigenic hormone secretion


What causes the the significant improvement of weight, inflammation and metabolic status after surgery?

Increased bacterial variety


Gut microbiota from GYGB treated mice to non -operated germ free mice

Caused weight loss and reduced fat mass - altered microbial production of short chain fatty acids


hedonic response to high calorie foods compared between RYGB and adjustable gastric banding

lower for RYGBs


Thermogenesis after RYGB - 2

decreased basal metabolic rate but increased meal induced thermosgenesis


RYGB and pancreatic exocrine function

impair it which could contribute to a small amt of fat malabsorption but probably too small to contribute to weight loss


will RYGB result in calorie malabsorption?

not likely


RYGB and unexplained chronic abdominal pain



Iron and RYGB

deficiency due to reduced acid production in the small stomach pouch


B12 and RYGB

deficiency in 70%


folic acid and RYGB

deficiency in 35%


RYGB and hypocalcemia & 25 -hydroxy vit D

hypocalcemia up to 10 % and low serum 25-hydroxy vit D levels in up to half


Major physiological changes that take place after RYGB

exaggerated release of satiety gut hormones with their central and peripheral effects on glycemia and food intake


Understanding the mechanisms of RYGB will

speed up the development of more effective and safer surgical and non-surgical treatments for obesity.


Is the challenge to lose weight?

no its to keep it off


Do diff diets of macros work differently?

no - modest diff in weight loss and metabolic risk factors - little diff in weight and health outcomes in time frames longer than 6 months


National Weight Control Registry looked at adults that have lost more than 13.6 kg of weight and kept it off for a year, tracking 10,000 people their strategies were - 3 +3

formal program
98% diet
94% PA
regular meal patterns -
prepare and eat at home
portion control - limit intake of food and quantity - count calories and food diary
weigh in daily


Additional ways of keeping weight off - 12

decrease total energy intake
decrease energy density
increased dietary fibre
decrease fat intake from fast foods
fewer sugar sweetened beverages
low sugar and low fat foods
decreased total alcohol intake
increased water intake
food diaries
increased PA (lifestyle and planned)
breakfast everyday
behavioural strategies - self monitor, food diary, weigh in, goal setting-fdbk


diet consistency

maintaining same diet regimen across the week and year instead of having cheat days is also important


PA and maintenance of weight loss

essential - less than 10% said they dont engage in PA - lifestyle and planned activities to balance the enery intake and expenditure


how to best use a diet to keep your weight off

Take one that you will find easiest to adhere to long term


How did the Twinkie diet work?

1800kcal cap, 2/3 came from junk food
- decreased LDL
- increased HDL
- decreased body fat
multivit everyday


4 treatment options for overweight and obesity

Lifestyle management - diet and PA
Pharmacotheraphy - Liraglutide (GLP-1 agonist) and Orlistat (Xenical)
Metabolic/bariatric surgery - indications: BMI>40, or >35 with diabetes
Not doing anything


What does Orlistat do?

inhibit the breakdown of fat


3 types of bariatric surgery

Roux-en Y gastric bypass
Sleeve gastrectomy
Adjustable gastric band


adjustable gastric band

if you filled the outside thing with saline you can adjust the opening and food wont go down as rapidly


if you reverse the surgery what happens to your weight

Comes back up


adverse effects of bariatric surgery - 6

post operational complications - 4% bleeding, perforations, leakage
mortality 0.1-2%, depending on surgery type
abdominal pain
vit b12, folate, and D deficiency - diff acids
calcium and iron deficiency
bone loss


4 mechanisms of bariatric surgery

increased delivery of food into the midgut
altered appetite and gut satiety hormones
increased thermic effect of food (increased metabolic rate of small bowel)
may be some fat malabsorption


7 altered appetite and gut satiety hormones

increase GLP1 and PYY for years - they dont have to wait for food to get down
ghrelin decreases
altered vagal signaling
altered bile acid signaling - enteroendocrine Lcells and Liver cells (metabolism and more satiety hormones)
modified gut microbiota composition and diversity
conditioned food avoidance due to dumping syndrome (glycemic issues)
reduced hedonic response to palatable food


how many people got bariatric surgery in 2013/14?

6500, increase of 300%


recidivism of weight management

reduced leisure time activity, dietary restraint, self weighing
increased energy intake from dietary fat and increased disinhibition


is our biology broken?

no, we just need to learn to deal with it