Prevalence of obesity worldwide

By 2025 global obesity prevalence is predicted to reach 18% in men and 21% in women.

• 6% of men and 9% of women (257 million adults worldwide) are predicted to live with severe/morbid obesity in 2025, a rapid increase from the last estimate (173 million) in 2014

Obesity is poised to affect 800 million adults by 2030 and is already a significant risk factor to all cause mortality, leading to 4 million annual deaths worldwide

• Obesity is mainly due to high calorie diet, processed food, sedentary lifestyle, low physical activity, industrialization
• Each 5 BMI point increase has been linked to a 30% increase in mortality and reduced life expectancy of 10 years

Bariatric and metabolic surgery effectively improves obesity related health risk factors and reduces all cause mortality

• Thus there has been a rapid rise in the number of primary and revision bariatric surgical procedures in the last 2 decades (before Covid-19 pandemic)
• During the Covid-19 period where there was a significant decrease in the number of bariatric operations performed

In 2019 ASMBS reported the rates of sleeve gastrectomy to be 59.4%, RYGBP 17.8% and revision bariatric surgery to be 16.7%

The recent 8^th IFSO publication also reported that revision bariatric surgery accounts for 6.5% of all procedures

It is understandable that the number of revision bariatric surgeries will continue to go up in the future

Chronic disease of obesity and sarcopenic obesity

Obesity is associated with excessive fat accumulation that leads to impair health, reduce quality of life and reduced life expectancy

• Patients are in a pro-inflammatory state with impaired metabolic pathways
• Associated with medical co-morbidities such as HPT, T2DM, cardio-vascular disease, renal disease, cancers and musculo-skeletal disease
• Obesity is associated with sarcopenia, progressive decline in skeletal or lean muscle mass/function (fat free mass FFM) with increasing fat mass (FM), exacerbating the metabolic disorder
  • Patients with sarcopenic obesity are more likely to suffer from hypertension, insulin resistance and has a higher risk of death and showed poorer weight loss results after surgery
  • Sarcopenic obesity is also associated with dyslipidaemia, metabolic syndrome, non alcoholic fatty liver disease, heart failure, osteoporosis 
  • FM/FFM ratio >0.8 is associated with significant cognitive decline
  • A more intensive exercise program is recommended for patients with sarcopenic obesity with a combination of aerobic plus resistance exercises/training

There is a reciprocal relationship between skeletal muscle and adiose tissue, axacerbated by factors such as aging, malnutrition, sedentary lifestyle, chronic inflammation, oxidative stress, insulin resistance in adipose tissues

This leads to muscle apoptosis, fat accumulation and compromised bone health

Post bariatric surgery changes in body composition aim to prevent loss of lean muscle FFM and improve muscle strength, which is important to functional capacity and overall well being of the patient

A multi component exercise training program may help to improve muscle strength for the lower limb and trunk (core strength)

Bariatric and Metabolic Surgery

Bariatric surgery is the most effective treatment for severe obesity and associated medical co-morbidities

• The criteria for surgery initially was published by NIH (in 1991) but has changed to follow the IFSO and ASMBS guidelines (in 2022)
• The sooner the intervention is performed the greater the probability of positive results
• But surgery is invasive, not reversible, drastic, has longer term side effects, risk and complications
• Septic complications and mortality can occur with bariatric surgery

Weight loss results of bariatric surgery

Losing weight is challenging and maintaining weight loss is even more difficult.

Successful weight loss may be 20-30% from the baseline pre-surgery weight.

But some studies reported that 20-50% of patients who undergo surgery may have inadequate weight loss (IWL) or weight regain

• IWL has been defined as <50% expected weight loss by 18months post op
• Weight regain has been defined as weight increase by >50% from the peak weight loss attained after bariatric surgery

Obesity is now regarded as a chronic relapsing disease and the cause is multi factorial

Weight regain can occur with time with all types of bariatric surgery

• Weigh regain resulting in a total net loss of 5% pre-operative weight has been reported in 3/3% of patients after RYGBP and 12.5% of patients after a sleeve gastrectomy 5 years after surgery

• After 10 years 30% of patients reported losing <20% of their pre-operative weight and 40% of patients have <50% excess weight loss (EWL)

One of the more acceptable indications for revision surgery include reflux or complications of sleeve gastrectomy and for remission of T2DM

However in general revision bariatric surgery are less effective as primary procedures, the risk and complications rate of revision surgery are much higher

Other benefits of bariatric and metabolic surgery

The results of surgery should not be viewed by simply based on the weight loss or BMI loss

There is a quantitative as well as qualitative measure of success of bariatric surgery

Bariatric and metabolic surgery helps to reduce the chronic inflammation

Bariatric and metabolic surgery can help improve mitochondria function by restoring mitochondrial morphology and reduce oxidative stress

Bariatric surgery may help with the physical improvement to the weight bearing joint and exercise tolerance

Bariatric and metabolic surgery may help with quality of life, employment, social and psychological aspects

Bariatric surgery may improve fertility rates in younger women with hormonal imbalance

Changes in mitochondria function

In normal patients mitochondria in the cells are responsible for metabolising nutrients to produce ATP, energy metabolism, generation of free radicals and calcium homeostasis, cell survival and cell death

• Glucose and lipid metabolism depend on mitochondria to generate energy in cells

In the obese patients, there is a lower demand for ATP and mitochondria generate excessive reactive oxygen species (ROS), which damages protein, DNA, lipid membrane components causing mitochondrial dysfunction

• Which in turn increases ROS, result in more oxidative stress, induces more inflammatory response, is related to insulin resistance and metabolic syndrome
• Mitochondria dysfunction leads to oxidative stress, cell death, inflammation and metabolic dysfunction

There have been many scientific studies into the role of mitochondria in the pathogenesis of metabolic problems such as obesity, metabolic syndrome and T2DM

Mitochondria dysfunction is characterized by abnormal mitochondria size, number, morphology, reduced autophagy, altered membrane potential and altered oxidative capacity

Electron microscopy have shown that there are fewer and smaller mitochondria in the skeletal muscle, liver, heart and adipose tissue in the obese, insulin resistant or T2DM patients

Bariatric surgery has been shown to induce several changes in the expression of genes encoding protein involved in mitochondrial action (fusion, fission, mitophagy, biogenesis) and the quality control of mitochondria

Bariatric surgery may result in restoration of mitochondrial architecture which result in metabolic improvements and increase mitochondria respiration

• Reduce reactive oxygen species, increase nitric oxide, decrease super oxide dismutase (SOD), decrease myeloperoxidase (MPO) activity and reduce systemic oxidative stress
• Leads to improvement in blood glucose and lipid profiles (higher HDL cholesterol)

Changes in gut microbiome

In obese patient unfavourable gut microbiome (increased firmicutes, decreased bacteroides) may lead to bacterial translocation and active inflammatory response

Bacterial overgrowth (after gastic bypass) may lead to production of metabolites such as lipopolysaccharide, which may affect immune cell secretion and inflammatory factors

Probiotic supplements may positively affect the microbiota, associated with decrease lipopolysaccharide, resolve inflammatory status and improve health

Obesity and cancer

Cancer is the second leading cause of death globally

Obesity is recognised as a risk factor for cancer due to the low grade chronic inflammation

Mortality from all cancers combined is 52% higher in male & 62% higher in females in the obese group

New IFSO guidelines and criteria for surgery in 2022 stated that

Bariatric surgery has been recommended as a bridging procedure before orthopaedic, abdominal wall hernia and transplant surgery

• Bariatric surgery has been shown to decrease operative time, length of hospital stay & early post op morbidity
• Leads to improvement in LV ejection fraction in patient awaiting heart transplant
• Reduce weight before cancer surgery

Hence to summarize: Visceral/central morbid obesity is a chronic relapsing disease Similar to T2DM it can be progressive and weight regain can occur after any types of non-operative intervention and bariatric surgery   We emphasize to patients not to view bariatric and metabolic surgery as a single entity   The primary aim of bariatric and metabolic surgery is for: Achieving significant total body weight loss Resolution of medical co-morbidities Reduce premature cardio-vascular mortality, cancer related and all cause mortality Improve health related quality of life Improve physical fitness, employment and psycho-social well being To help patient change eating behaviour/habits, improve food choices and make positive lifestyle changes   On a microscopic level metabolic surgery is also to: Reduce secretion of inflammatory mediators and chronic inflammation Improve mitochondria/cell function Improve gut microbiome and bile salt metabolism