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(bariatric surgery (or weight loss surgery) includes a variety of procedures performed on people who
are obese. Long term weight loss through the standard of care procedures (roux en-y bypass, sleeve
gastrectomy, and biliopancreatic diversion with duodenal switch) is largely achieved by altering gut
hormone levels responsible for hunger and satiety, leading to a new hormonal weight set point. Bariatric surgery is the most effective treatment causing weight loss and reducing complications of
Bariatric surgery can have significant health benefits in addition to weight loss, including
improvement in cardiovascular risk factors, fatty liver disease, diabetes management, and reduction
in mortality.
Each type of procedure exerts its effects through at least one of three mechanisms: restricting food
intake, decreasing nutrient absorption, or affecting the body’s cell signaling pathways. Often,
procedures affect several of these mechanisms.
Restricting food intake
This is accomplished by reducing the size of the stomach that is available to hold a meal, (for example,
gastric sleeve or stomach folding, see below). Filling the stomach faster enables an individual to feel
more full after a smaller meal.
Decreasing nutrient absorption
Some procedures work by reducing the amount of intestine that food passes through. For example, a
roux-en-y gastric bypass connects the stomach to a more distal part of the intestine, which reduces the
ability of the intestines to absorb nutrients from the food.
Affecting cell signaling pathways
While bariatric procedures may have initially been targeted at reducing intake and absorption, studies
have shown additional affects on the hormones that dictate hunger (e.g. ghrelin) and satiety (leptin).
This is especially important when considering the durability of weight loss compared to lifestyle
changes. While diet and exercise are essential for maintaining a healthy weight and physical fitness,
metabolism typically slows as the individual loses weight, a process known as metabolic
adaptation. Thus, efforts for obese individuals to lose weight often stall, or result in weight regain. Bariatric surgery is thought to affect the weight “set point,” leading to a more durable weight
loss. This is not completely understood, but may involve the cell-signaling pathways and
hunger/satiety hormones.

Medical uses
Bariatric surgery has proven to be the most effective obesity treatment option for durable weight loss
] along with this weight reduction, the procedure has significant health benefits ranging from reduced cardiovascular risk factors, remission of type 2 diabetes, reduced fatty liver disease, lower incidence
and severity of depression syndromes, among others
As surgery is contraindicated with a medically correctable cause of obesity, substance abuse,
concurrent or planned pregnancy, eating disorder, or inability to adhere to postoperative
recommendations and mandatory lifestyle changes.
When counseling a patient on bariatric procedures, providers should take an interdisciplinary
approach. Psychiatric screening is also critical for determining postoperative success. Patients with a
body-mass index of 40 kg/m2 or greater have a 5-fold risk of depression, and half of bariatric surgery
candidates are depressed. Some people with disordered eating may not be able to follow postoperative dietary guidelines.

Weight loss
In adults, the malabsorptive procedures lead to more weight loss than the restrictive procedures;
however, they have a higher risk profile.
In children and teens, evidence for the effectiveness of bariatric surgery is more context-specific. A
2017 meta-analysis found bariatric surgery to be effective for weight loss in adolescents 36 months
after the intervention and that additional data was needed to determine whether it is also effective
for long-term weight loss in type 2 diabetes mellitus.
Type 2 diabetes is characterized by the body’s resistance to the hormone insulin, which results in high
blood sugars and a range of complications including increased risk of heart attack, retinopathy, kidney
failure, and peripheral neuropathy. Recent studies have shown that patients who have undergone
bariatric surgery can often maintain their blood sugars within acceptable levels while discontinuing
their diabetes medications.[15][24] this may essentially amount to a ‘cure’ for diabetes. Prior to the
updated guidelines asmbs/ifso, international diabetes organizations had recommended considering
bariatric surgery in people with a bmi over 30 who have type 2 diabetes and poorly controlled

Reduced mortality and morbidity
A meta-analysis of 174,772 participants published in the lancet in 2021 found that bariatric surgery
was associated with 59% and 30% reduction in all-cause mortality among obese adults with or
without type 2 diabetes respectively. This meta-analysis also found that median life-expectancy was
9.3 years longer for obese adults with diabetes who received bariatric surgery as compared to routine
(non-surgical) care, whereas the life expectancy gain was 5.1 years longer for obese adults without
Bariatric surgery in older patients has also been a topic of debate, centered on concerns for safety in
this population; the relative benefits and risks in this population is not known.

Fertility and pregnancy
It was not clearly understood whether medical weight-loss treatments or bariatric surgery had an
effect responsiveness to subsequent treatments for infertility in both men and women. Bariatric
surgery reduces the risk of gestational diabetes and hypertensive disorders of pregnancy in women
who later become pregnant but increases the risk of preterm birth.[28]
Bariatric surgery had an effect responsiveness to subsequent treatments for infertility in both men and
women bariatric surgery reduces the risk of gestational diabetes and hypertensive disorders of
pregnancy in women who later become pregnant but increases the risk of preterm birth.
Mental health
Among the patients who seek bariatric surgery, pre-operative mental health struggles are
common. Some studies have suggested that psychological health can improve after bariatric surgery,
due in part to improved body image, self-esteem, and change in self-concept—these findings were
also present in pediatric populations. Bariatric surgery has consistently been associated with
postoperative decreases in depressive symptoms and reduced severity of symptoms. Importantly, the
surgery may not affect everyone the same way, and there are potential adverse effects outlined in the
next section.

Adverse effects
Weight loss surgery in adults is associated with relatively large risks and complications, compared to
other treatments for obesity.
The likelihood of major complications from weight-loss surgery is 4%. “sleeve gastrectomy had the
lowest complication and reoperation rates of the three (main weight-loss surgery) procedures…..the
percentage of procedures requiring reoperations due to complications was 15.3 percent for the gastric
band, 7.7 percent for gastric bypass and 1.5 percent for sleeve gastrectomy,” according to a 2012
study by the american society for metabolic and bariatric surgery.[34] over a 10-year study while
using a common data model to allow for comparisons, 8.94% of patients who received a sleeve
gastrectomy required some form of reoperation within 5 years compared to 12.27% of patients who
received a roux-en-y gastric bypass. Both of the effects were fewer than those reported with
adjustable gastric banding.
As the rate of complications appears to be reduced when the procedure is performed by an
experienced surgeon, guidelines recommend that surgery be performed in dedicated or experienced
units.it has been observed that the rate of leaks was greater in low volume centres whereas high
volume centres showed a lesser leak rate. Leak rates have now globally decreased to a mean of 1-5%.
Postoperative complications

Laparoscopic bariatric surgery requires a hospital stay of only one or two days. Short-term
complications from laparoscopic adjustable gastric banding are reported to be lower than
laparoscopic roux-en-y surgery, and complications from laparoscopic roux-en-y surgery are lower than
conventional (open) roux-en-y surgery.
Risks of roux-en-y gastric bypass include anastomotic stenosis (narrowing of the intestine where the
two segments are rejoined), marginal ulcers (ulcers near the rejoined segment), internal hernia, small
bowel obstruction, kidney stones, and gall stones. Sleeve gastrectomy also carries a small risk of
stenosis, staple line leak, and gastro-esophageal reflux disease (also known as gerd, or heartburn).
In addition to procedure-specific risks, patients also face risks to surgery in general. Pulmonary
embolism is another common adverse complication of bariatric surgery.[39] pulmonary embolism
occurs due as a result of deep vein thrombosis, in which blood clots form in the deep veins of the
extremities, usually the legs. If not treated, the clot can travel to the heart and then to the lung. This
adverse effect is simply prevented by heparin and lmwh, which are both blood thinning medications.
Dumping syndrome
Dumping syndrome is a condition characterized by quick emptying of the stomach and frequent bowel
movements. It is more common following rygb than sg, and can typically be treated through dietary

Metabolic bone disease
Metabolic bone disease manifesting as osteopenia and secondary hyperparathyroidism have been
reported after roux-en-y gastric bypass surgery due to reduced calcium absorption. The highest
concentration of calcium transporters is in the duodenum. Since the ingested food will not pass
through the duodenum after a bypass procedure, calcium levels in the blood may decrease, causing
secondary hyperparathyroidism, increase in bone turnover, and a decrease in bone mass. Increased
risk of fracture has also been linked to bariatric surgery.

Cholelithiasis (gallstones)
Rapid weight loss after obesity surgery can contribute to the development of gallstones by increasing
the lithogenicity of bile. Estimates for prevalence of symptomatic cholecystitis after roux-en-y gastric
bypass range from 3-13%.[15] cholelithiasis can be managed with a removal of the gallbladder
Renal effects
Adverse effects on the kidneys have been studied. Hyperoxaluria that can potentially lead to oxalate
nephropathy and irreversible renal failure is the most significant abnormality seen on urine chemistry
studies. Rhabdomyolysis leading to acute kidney injury, and impaired renal handling of acid and base

has been reported after bypass surgery additionally, nephrolithiasis (kidney stones) are common after
roux-en-y gastric bypass, with estimates of prevalence ranging from 7-11%.
Nutritional deficiencies
Deficiencies of micronutrients like iron, vitamin b12, fat soluble vitamins, thiamine, and folate are
especially common after mal-absorptive bariatric procedures. Seizures due to hyperinsulinemic
hypoglycemia have been reported. Inappropriate insulin secretion secondary to islet cell hyperplasia,
called pancreatic nesidioblastosis, might explain this syndrome.
Mental health
Though many benefits to mental health are described above, there are several potential adverse
effects that should be discussed. Alcohol problems have been reported to be more common in patients
who have undergone gastric bypass surgery. Of note, patients who receive an rygb may reach a higher
peak alcohol concentration more quickly, due to changes in their metabolism.in addition, self-harm
behaviors and suicide appear to be increased in people with mental health issues in the five years
after bariatric surgery had been done.)
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