Background

Obesity affects almost half the adult population Morbid obesity (BMI >40) is strongly related to metabolic conditions, especially T2DM (20%), HPT (50%) and dyslipidaemia (70%) Combinations of metabolic disorders significantly increase morbidity and early mortality   Management plans is a combination of *Dietary and lifestyle modification *Pharmacotherapy (before surgery) *Primary bariatric and metabolic surgery *Adjunct anti obesity medications (after surgery) *Further revision conversion bariatric metabolic surgery   The best clinical outcome is not weight control alone but also incorporate improvement in metabolic parameters, health related quality of life, reduction in cardio-vascular complications, premature mortality, etc   The optimal management plan requires a team of healthcare and allied health providers, mainly including the GP, endocrinologist, bariatric surgeon and a team of support staff (dietitian, exercise physiologist, psychologist) to: *Achieve the sustained weight management *Achieve the clinical health improvements *Prevent weight regain or relapse back to bad eating habits and food/substance addiction   Most patients can achieve the first two goals with some degree of support *Some patients far exceed their weight loss goals and health improvement *However almost all patients will experience weight regain with the passage of time and return of some of the metabolic conditions due to many reasons (multifactorial reasons for weight regain) *Hence there obesity is now regarded as a chronic relapsing disease with adjunct management options (in the form of GLP-1 injections) being discussed after the initial/primary bariatric surgery     The motivation for primary bariatric metabolic surgery may be very different amongst individual patients. The important thing to note is that: *The criteria for metabolic and bariatric surgery as published by IFSO/ASMBS 2022 should be followed *The surgery is not for cosmetic purposes but for reduction of metabolic/clinical problems associated with obesity and its complications *Patients physical/functional status and mental well being is also a factor to be considered regarding the severity or impact of obesity

Assessment for obesity and metabolic disorders There are many methods used to measure the degree of obesity and its impact on health There are many parameters used to predict the cardio-vascular risk factors and mortality   Some are easy to measure and well known (eg. body weight, BMI, waist circumference) Others are mathematical formulas (eg. WHR, waist:height ratio, RFM, VAI) The more invasive or gold standard investigation is the DEXA scan   There are also different obesity staging system   No single measure or staging system is complete But it is very helpful to understand how obesity affects different patients in so many different ways eg. a lower BMI patient with central/visceral obesity may have a higher mortality risk than a taller obese patient who does not have T2DM or pre-existing coronary artery disease

Simple measurements for obesity

Body Mass Index (kg/m2)

Normal	18.5 – 24.9
Overweight	25 – 29.9
Class 1	30 – 34.9
Class 2 (moderate)	35 – 39.9
Class 3 (severe)	40 or greater

Waist circumference

Waist circumference predicts risk of future coronary artery events and all cause mortality

• Every 5cm increase in waist circumference is associated with 17% increase mortality in men and 13% in women

Below is a study on risk stratification based waist circumference published for Caucasian and non Caucasian population

Nationality	Normal	Overweight	Class 1	Class 2
White men	>90cm	>100cm	>110cm	>125cm
White women	>80cm	>90cm	>105cm	>115cm
African men	>78cm	>92cm	>104cm	>119cm
African women	>76cm	>85cm	>97cm	>110cm

Waist hip ratio or waist/hip circumference ratio (WHR)

This is waist hip ratio is used to assess accumulation of abdominal fat (central/visceral obesity)

• WHR >1 (men) or >0.8 (women) indicate excess abdominal fat

WHR has been associated with increase all cause mortality, cardio-vascular risk factor, T2DM

Waist height ratio (waist/height)

This is WHR adjusted for height

The normal range is 0.46 to 0.62

Waist height ratio is a better predictor for HPT, T2DM, dyslipidaemia than BMI

Relative fat mass (RFM)

The DEXA (dual energy X-ray absorptiometry) is the gold standard for measuring body composition

RFM is the better predictor of % body fat than BMI

RFM >40% (women) and 30% (men) have a higher risk for mortality

Estimated RFM is calculated using the formula

Men RFM = 64 – (20 x height/waist circumference)

Women RFM = 76 – (20 x height/waist circumference)

Visceral adiposity index (VAI)

VAI predicts all cause mortality in older adults

Estimated VAI is calculated using the formula

Men VAI = [waist circumference/39.68 + (1.88 x BMI)] x (triglyceride/1.03) x (1.31/HDL cholesterol)

Women VAI = [waist circumference/36.58 + (1.89 x BMI)] x (triglyceride/0.81) x (1.52/HDL cholesterol)

Body composition study   Introduction Total body mass compose of bone, skeletal muscle, organ, water, essential fat and non essential fat.   There is fat mass and fat free mass (lean body mass as described above). *The skeletal mass and water mass is the heaviest *Triglyceride is stored in the adipose tissue *There is also fat inside the organs (ectopic fat), eg. liver which contribute to fatty liver disease (steatohepatitis, liver cirrhosis) or muscle, eg intramycellular triglyceride problems (insulin resistance, T2DM)   The body adipose tissue is either within the abdominal cavity (visceral fat which makes up 5-10%) or outside the abdominal cavity (subcutaneous fat, 80%). *It is the visceral fat that is associated with increased cardio-vascular risk and mortality risk   10% increase in body fat percentage is associated with a mortality hazard of 1.11 Each 5kg increase in fat is associated with a mortality hazard ratio of 1.06   Loss of muscle mass (weak, loss of function) with obesity and metabolic problems is termed sarcopenic obesity   Measurements There are few methods to directly or indirectly (through mathematical equations) measure the amount of fat in the body, these include: *Skinfold thickness *Hydrostatic underwater weighing (densitometry) and air displacement plethysmography (Body Pod inside a fibre glass chamber) *Bioelectrical impedance (skin electrodes using electrical conduction through fat and lean body mass, measuring the phase angle from the body resistance and capacitive reactance) *Dual energy X-ray absorptiometry (DEXA) *CT scan or MRI scans   DEXA is the gold standard for measuring bone mineral density *DEXA can also differentiate between fat mass and fat free mass (lean tissue) and calculations for body fat mass, % body fat, fat mass index, adiposity index and lean index can be calculated *and reported as a percentile against age matched control and gender specific controls *it is important to monitor weight loss, fat loss but also try to preserve lean body/muscle mass and bone health after bariatric metabolic surgery *but DEXA may be limited for the super obese patient, also a small dose of radiation is involved   CT scan can measure the subcutaneous and visceral adipose tissue thickness MRI scan can be used to estimate the total fat volume instead of specifically measuring the subcutaneous or visceral fat thickness *It doesn’t have any radiation involve but may be limited by cost and not for the super obese

Staging system

At the present time there is no standardized scoring system for the severity of obesity related medical disorders, however there are a few currently in place, these include:

• Edmonton Obesity Staging System
• King’s Obesity Staging Criteria
• American Diabetes Association (ADA) 2022 diagnostic and treatment criteria (optimally treated T2DM is HbA1C <7 with pharmacotherapy)
• Assessment of Obesity Related Conditions (AORC) adopted by ASMBS
• Bariatric Analysis and Reporting Outcome System (BAROS) 1998 to address the immediate and long term outcomes after bariatric surgery
• In Australia The Bariatric Surgery Registry (BSR) was set up to report weight loss outcome, control of T2DM and complications after bariatric surgery
• The scoring system is more useful than focusing on the individual patient weight, BMI, waist circumference or body composition alone

Assessment of Obesity Related Conditions (AORC)

Type 2 diabetes mellitus

Scores	Medication	Clinical definition
0	No	No DM (HbA1C <5.7)
1	No	Insulin resistance or pre-diabetes (HbA1C 5.7-6.4)
2	Oral	DM controlled with oral medications (HbA1C 6.5-8.4)
3	Insulin	DM controlled with insulin (HbA1C <7)
4	Oral + insulin	DM controlled with oral medications and insulin (HbA1C <7)
5	All medications	DM not controlled with medications or with complications (HbA1C >8.5)

Hypertension

Scores	Medication	Clinical definition
0	No	No HPT (BP <120/80)
1	No	Pre HPT (BP 120-139/80-89)
2	No	HPT controlled with lifestyle changes (BP <140/90)
3	Single	HPT controlled with single medication (BP <140/90)
4	Multiple	HPT controlled with multiple medications (BP <140/90)
5	All medications	HPT not controlled with medications or with complications (BP >140/90 or >160/100)

Dyslipidaemia

Scores	Medication	Clinical definition
0	No	No dyslipidaemia
1	No	Pre dyslipidaemia
2	No	Dyslipidaemia controlled with lifestyle changes
3	Single	Dyslipidaemia controlled with medication
4	Multiple	Dyslipidaemia controlled with medications
5	All medications	Dyslipidaemia not controlled with medications

Edmonton Obesity Staging System

Stage	Description
0	No obesity related risk factors, no physical symptom, no psychological symptom, no functional limitations
1	Subclinical risk factors (borderline HPT, impaired fasting glucose, elevated liver enzymes) Mild physical symptoms (shortness of breath on exertion, ache/pain, fatigue) Mild psychological symptoms or mild impairment of well being (not affecting quality of life)
2	Has obesity related co-morbidities requiring medical intervention (HPT, T2DM, OSA, PCOS, OA, GOR) Moderate obesity related psychological symptoms (eating disorder, anxiety, depression)
3	Has significant obesity related end organ damage (AMI, cardiac failure, T2DM complications, incapacitating OA) Significant obesity related psychological symptoms (major depression, suicidal ideation) Significant functional limitations (unable to work, compromise routine activities, reduced mobility) Significant impairment of well being (quality of life)
4	Severe potentially end stage obesity related co-morbidities Severe disabling psychological symptoms Severe functional limitations

King’s Obesity staging Criteria

Stage	Description
0	Airway normal, neck circumference <43cm BMI (not meet criteria for surgery) Cardiovascular risk (<10%) T2DM (HbA1C <5.7) Economic complication none Functional limitation >3 hours moderate physical activity/week Gonadal dysfunction normal Health status, mental image normal
1	Airway mild OSA, neck >43cm, asthma or COAD BMI 35-39.9 Cardiovascular risk 10-19% T2DM (HbA1C 5.7-6.4 Economic complication none Functional limitation 1-2 hours moderate physical activity/week Gonadal dysfunction hyperandrogenaemia Health status, mental image anxiety/depression without medication
2	Airway OSA requires CPAP BMI 40-50 Cardiovascular risk >20% stable coronary artery disease T2DM (HbA1C <9) Economic complication workplace disadvantage Functional limitation <1 hour moderate physical activity/week Gonadal dysfunction PCOS Health status, mental image psychoactive drug, eating disorder
3	Airway severe OSA BMI >50 Cardiovascular risk high T2DM (HbA1C >9) Economic complication disabled Functional limitation Gonadal dysfunction Health status, mental image