Diabetes mellitus link with overweight and obesity is very clear and observed in most population in the world. The global prevalence of diabetes in 2019 is 9.3% affecting 463 million people. The prevalence is expected to raise to 10.2% by 2030 and 10.9% in 2045 [20]. International Diabetes Federation estimated that in 2019 the global expenditure on diabetes mellitus that accounts for the direct cost is USD 760 billion. This figure will raise to USD 825 billion in 2030 and USD 845 billion to 2045 [11]. Abdullah et al. [1] in a metaanalysis of 18 prospective cohort studies found that the relative risk of diabetes among the obese was 7.19 and the overweight was 2.99 compared to those with normal weight. Most of the studies that estimated the obesity and overweight cost of diabetes mellitus used the population attributable fraction (PAF) method. In UK, obesity and overweight contributes 79% of PAF of diabetes cost or 2.1% of the total annual DALYs lost. This is equivalent to £533 million in 2002 [2]. In an earlier study conducted by Birmingham et al. [13] in Canada the PAF for obesity in diabetes was estimated to be 50.7%. The total direct cost of diabetes mellitus attributable to obesity was CAD 423 million per year.

Osteoarthritis is one of the major musculoskeletal conditions related to obesity. Study among women in UK found that highest tertile of BMI were six times more likely to develop osteoarthritis [21]. It was observed in another study that for every one standard deviation (SD) increase in BMI, the risk of developing osteoarthri­tis is increased by 40%. The PAF for obesity in osteoarthritis was estimated to be 21% in UK. The total cost of obesity in osteoarthritis was estimated to be around £229 million per year [2]. Chen et al. [8] in their reviews of series of literatures from North Americans, European and Asian regions reported that there are huge variation in the direct and indirect cost of managing osteoarthritis in these regions. The cost of topical and oral NSAID ranged from £19.2 to £26.65 million per year while the cost of knee and hip replacement exceeded £850 per year. The indirect cost of osteoarthritis due to loss of productivity was estimated to be £1.34 billion per year. In Spain, Loza et al. [16] estimated that the direct and indirect cost of osteoarthritis was £4.04 billion and £654 million per year, respectively. Based on PAF estimation from the study in UK, the cost of osteoarthritis due to obesity in Spain was £986 million per year. Le Pen et al. [14] conducted an economic bur­den study of osteoarthritis in France. They estimated that the total direct cost of

Obesity and overweight are two known risk factors of cancers. In 2018, it was estimated there were 18.1 million cancer cases and 9.6 million deaths globally. Risks of 13 types of cancers increased with obesity and overweight that account for 3.6% new cancers among adults worldwide [7]. Cancers that are linked to obe­sity and overweight includes colon, endometrium, postmenopausal breast, kidney, esophagus, pancreas, gallbladder, liver, and hematological malignancy [23]. The overall cost of expenditure on cancers in US in 2017 was estimated to be USD 342 billion, which is equivalent to 1.8% of GDP. Loss of productivity and cost of pre­mature deaths is 53% of the total cost. In the European Union the cost of cancer was estimated to be €141.8 billion or 1.07% of the total GDP.

Breast cancer is the most common cancer among women and accounted for 12% of all cancer cases globally. The cumulative risk of developing breast cancer among women age 75 years is 5%. The PAF for obesity and overweight in breast cancer was estimated to be around 12% in UK. Obesity and overweight is respon­sible for 1.8% of the total DALYs loss due to breast cancer. The total cost of breast cancer attributable to obesity and overweight in UK was £29 million per year [2]. A study in Canada reported that the obesity and overweight cause of breast can­cer was CAD 19.8 million year. However, this study focussed on postmenopausal women and the PAF of 9.1% was used [13].

Overweight and obesity is a major public health problem in both developed and developing countries. Costing studies on these conditions can provide excellent insight to the policy makers on the scale of the problems that affect the health system. Outcome of such studies highlighted the significant amount of resources

required in managing cases of overweight and obesity. The overall health expend­iture to manage overweight and obesity ranged from 2% to as high 12% of the total national health expenditure. However, there are wide variations in the cost­ing methods to estimate the direct and indirect cost as reported in the reviewed studies. Most of the studies employed the step-down approach in combination with PAF to estimate the total cost. Step-down costing was the preferred method in most of the studies because of lack of detail costing information required in activity-based costing. There is also wide range of PAF values depending on the countries where the study was conducted and the conditions linked to obesity and overweight. PAF values were as high as 79% for diabetes mellitus and was only

4.7% for colorectal cancers. One of the major future challenges for the researchers is to work towards standardization of the costing methods in order to increase the usability of the study outcome for policy decisions.

Most cardiovascular disease is increased in the setting of obesity, including coro­nary heart disease, heart failure with reduced ejection fraction (HFrEF), heart fail­ure with preserved ejection fraction (HFpEF), atrial fibrillation and stroke [10–11]. Obesity contributes to these diseases via both indirect and direct effects on the cardiovascular system. The indirect effects are well known and include hyper­lipidemia, dyslipidemia, arterial hypertension, insulin resistance, hyperglycemia, and systemic inflammation [10]. These cardiometabolic risk factors correlate with fat mass in obesity, and particularly with visceral and ectopic fat depots that are known to have systemic metabolic effects [12].

centers have implemented BMI thresholds resulting in an increased demand for more effective weight loss options in this population [30].

Due to the adverse effect of obesity on transplant outcomes, many transplant