The Global Burden of Obesity and Diabetes

(1)

Baker IDI Heart & Diabetes Institute, Clinical Obesity Research, Melbourne, VIC, Australia

Keywords

PandemicDiabesityGlobalBurdenEpidemiologyWeight lossRegional variation

One could only wonder what aliens who visited Earth briefly 40 years ago and returned today would think of the changes seen in the dominant intelligent life form inhabiting the planet. Large numbers of humans have become quite bloated, sluggish, and many have difficulty getting around. This would appear the most obvious change in the human condition during that period. What has happened? What has gone wrong? What will things be like should our visitors return in another 40 years?

The obesity-diabetes epidemic has rolled out progressively and inexorably since the 1970s, and little has been done globally to prevent it. The causes are poorly understood, and any attempts to change the trends appear piecemeal, tokenistic, and ineffective. Regions of the developing world that appeared to be protected with their economic and lifestyle characteristics are surpassing all expectations, and even those in rural areas of developing countries are running head first into the diabesity epidemic.

Obesity a Global Issue: The global age-standardized prevalence of obesity nearly doubled from 6.4 % in 1980 to 12.0 % in 2008. Half of this rise occurred in the 20 years between 1980 and 2000 and half occurred in the 8 years between 2000 and 2008 [1]. The magnitude of rise has varied with region, country, and gender; however, stabilization of the obesity prevalence is rare, and of great concern, the rise has accelerated globally over the last decade. In 1980, half of the 572 million adults with a BMI >25 kg/m² lived in just five countries headed by China 72 million and the USA 70 million. In 2008, countries with the most overweight people were China (241 million) and the USA (158 million). The largest absolute rise in obesity (BMI >30 kg/m²) occurred in the USA (56 million) and China (42 million), followed by Brazil (20 million) and Mexico (18 million). The region with the highest global prevalence of obesity includes small islands in the Western Pacific such as Nauru, Samoa, Tonga, and the Cook Islands where obesity rates exceed 50 % and for some subgroups 70 % [1].

Of the high-income nations, there were divergent trends for both men and women with greater rises in obesity prevalence in Australasia and North America compared with Western Europe and high-income areas of Asia. Women had greater increases in obesity prevalence than men in sub-Saharan Africa and Latin America and the Caribbean. Men had greater a increase in prevalence throughout Europe and the high-income regions of the Asia-Pacific region [1]. “If the rates of weight gain (in Australia) observed in the first 5 years of this decade are maintained, our findings suggest that normal-weight adults will constitute less than a third of the population by 2025, and the obesity prevalence will have increased by 65 %” [2].

With increasing levels of obesity, we see an exponential rise in class III obesity (BMI > 40 kg/m²). In the USA between 2000 and 2005, the prevalence of obesity increased by 24 %, class III obesity by 50 %, and BMI >50 kg/m² by 75 %, two and three times faster, respectively [3]. Similar trends are reported in Australia [4]. The resultant exponential increase in class III obesity and super obesity is an expected trend as the mean BMI for a community steadily increases. There is also an important gender trend with increasing levels of obesity with women more likely to have the more severe forms of obesity Table 1. Scattered reports of a leveling off of obesity prevalence in small subsections of the community, for example, in adolescent and young adult women, should be treated cautiously as levels are still high, and we need to reflect about the weight trajectories of their mothers and grandmothers who at an equivalent age were generally more petite.

Table 1.

Estimates of the proportion of the US adult population with a BMI > 40 kg/m²

	1960 (%)	1980 (%)	2000 (%)	2010 (%)
Women (USA)	1.4	2.8	6.1	7.4
Men (USA)	0.4	0.8	2.9	4.3

Adapted from the IASO website [5]

For years we have watched as the US CDC state by state obesity levels have risen year by year and reassured ourselves that either our state was not the worst or, better still, we lived outside the USA and were immune to the catastrophe within. But alas, we can now watch similar changes in the Canadian provinces and UK counties, and thanks to the International Association for the Study of Obesity (IASO), we have a global atlas of the emerging trends. Sadly no global area is or will remain immune.

Ethnic Differences Risk: Ethnic-Based Action Points

Diabetes as a Global Issue: While it can be often assumed that the emerging epidemic of type 2 diabetes parallels the obesity epidemic, there are a range of other important considerations that influence the global and regional incidence, prevalence, and total burden of type 2 diabetes.

The International Diabetes Federation “World Diabetes Atlas” updated in 2012 provides an excellent overview of the global situation, and there are very important regional considerations. Globally it is estimated that 371 million live with diabetes, an overall adult prevalence is 8.3 %, and half of these cases are undiagnosed:

Countries with the highest prevalence of diabetes are in two regions the Western Pacific Island nations and in the Middle East. Examples of the highest prevalence rates in adults include Federation of Micronesia (37 %), Nauru (31 %), and Marshall Islands (27 %) in the Western Pacific and Kuwait (24 %), Saudi Arabia (23 %), and Qatar (23 %) in the Middle East.
Countries with the highest absolute numbers in descending order are China (92 million), India (63 million), the USA (24 million), and Brazil (14 million). And the region with the highest numbers is the Western Pacific with 132 million.
Sub-Saharan Africa is the region with the highest level of undiagnosed diabetes (80 %).

It is the Asian area that now contributes to more than 60 % of the world’s population with diabetes where some of the most dramatic increases in diabetes prevalence have occurred over recent decades. All Asian countries have seen major rises as the rapid socioeconomic growth and industrialization interact with populations that have a strong genetic and ethnic risk of diabetes. Asians develop diabetes at a lower threshold of environmental and anthropometric risk (BMI and waist circumference) [6]. Another striking characteristic of diabetes in the Asian region is the striking narrowing of the urban–rural divide in diabetes prevalence. While urbanization and industrialization were thought to drive increased risk of diabetes, it is now clear that the rural areas are following very closely behind. In the Shanghai region of China, urban diabetes prevalence rose from 11.5 to 14.1 % between 2002–2003 and 2009, while the rural diabetes prevalence rose from 6.1 to 9.8 % during the same period [7]. The rapid rise in diabetes numbers in China indicates a major public health problem that has occurred in parallel with the massive changes in development and gross domestic product [8].

A recent review of diabetes prevalence in the rural areas of low- and middle-income countries revealed a quadrupling of prevalence over the last 25 years. Diabetes prevalence increased over time, from 1.8 % in 1985–1989, 5.0 % in 1990–1994, 5.2 % in 1995–1999, 6.4 % in 2000–2004, to 8.6 % for 2005–2010 [9]. However, this is only part of the story as it is estimated that between 2010 and 2013, the number of adults with diabetes will increase by 69 % in developing countries, while the expected increase in developed countries is 20 % [10]. The diabetes burden in developing countries is also troubling as the increase in diabetes prevalence is dominated by the 40–59 age group, a time of productivity and employment, rather than being driven by aging as is the case developed countries (Fig. 1) [10].

Fig. 1.

The predicted number of people with diabetes in 2030 in comparison with 2010 (adapted from: Shaw, J.E. et al., Diabetes Res Clin Pract, (2010). 87(1): p. 4–14).

Factors influencing the number of people with diabetes also vary considerable between developed and developing countries. If the incidence of diabetes exceeds mortality, then the prevalence rises. The absolute number of people with diabetes will be influenced by a range of factors, and the relative contributions of these factors vary considerably (Fig. 2). An increased prevalence of diabetes is not simply related to an increase incidence. In the period between 1999 and 2004 in Taiwan, the prevalence of diabetes increased 38 % and 24 % in men and women, respectively, but during the same period, incidence dropped 4 % and 13 %, respectively. An increased incidence in younger adults and a reduced incidence in the elderly increased prevalence substantially [11].

Fig. 2.

The reasons associated with an increase in the numbers with diabetes. The relative impact of these population characteristic varies considerably between developed and developing countries.

Diabetes incident and prevalence data from Ontario Canada between 1995 and 2005 provides another example of the interactions that lead to prevalence. During this period, the age- and sex-adjusted prevalence of diabetes in the province increased 69 %, from 5.2 % in 1995 to 8.8 % in 2005. The rate of increase in prevalence was greater in a younger population and the mortality of those with diabetes fell by 25 %. Thus, the increased prevalence in diabetes is attributed to both an increased incidence and improved survival [12].

The prevalence of diabetes in the USA is also greatly influenced by an increased survival of those with diabetes. During the period 1997 to 2004, the National Health Interview Survey found that age-adjusted excessive death rates for those with diabetes (compared with those without diabetes) declined by 60 %, from 5.8 additional deaths/1000 to 2.3 additional deaths/1000, for cardiovascular disease, and for all-cause age-adjusted mortality a decline of 44 % from 10.8 to 6.1 deaths/1000. The declines were similar in both men and women [13]. Similar declines in mortality have been reported in other developed countries including Canada, Norway, and Finland. These encouraging findings have been attributed to a range of advances including systematic improvements in the quality and organization of care, improved models of chronic disease management, and the active promotion of self-care behaviors. More intensive pharmacotherapy targeting optimal levels of blood pressure [14] and cholesterol [15] has been shown to reduce morbidity and mortality, while the targets for glucose control remain more controversial [16]. There have also been reductions in smoking, limb amputations, and visual loss associated with retinopathy.

It becomes clear that while increasing levels of obesity play a major role in the increasing global population with diabetes, there are other major contributing determinants. The contrast in these determinants in developing compared with developed nations is presented in Table 2.

Table 2.

The differing determinants of the increasing population with diabetes in developing compared with developed countries