**4. Causes of the high prevalence rate of diabetes in South Asians**

#### **4.1. Physiological and traditional causes**

#### *4.1.1. Genetic factors*

In this section, we explore why the prevalence rate of diabetes in South Asia is so much higher than in other developed or developing countries. Among the causes, genetic factors seem to be important, as a study suggested that 30–70% of the diabetes risk could be attributed to genetic variants (SNPs of diabetic genes) [32]. Genetic variants causing diabetes have been screened since the 1990s [33]. Around 50 genetic variants, known as "obese genes" or "thrifty genes" have been identified, and the relationship between diabetes and genetic variants of β3-adrenalin receptor—a thrifty gene—have been examined in particular detail. Individuals with a variant genotype of a thrifty gene proactively store fat in the body by reducing the energy metabolism; this is beneficial in times of nutrient scarcity [34, 35]. Asian populations are much more likely to possess thrifty genotypes than Europeans. The reason for this is believed to be because South Asian populations have not had sufficient time to adapt from this variant genotype to a normal genotype, as Europeans evolved in environments where they were relatively unaffected by famine cycles [32].

Several studies have reported that South Asians have several risk factors for disorder of glucose consumption and insulin resistance. For instance, features of insulin resistance, such as hypertriglyceridemia, and increased abdominal or visceral fat have been seen even in nonobese Asian populations [36–38], and South Asians have more adiposity than Europeans and residents of other parts of the world with the same body weight [39, 40]. Furthermore, South Asians are more insulin resistant than other races [36, 41]. Studies conducted in India as representative South Asians have reported that Indians were at a higher risk of glucose intolerance than Europeans, even in groups with a low waist circumference [42, 43]. Insulin resistance and compensatory hyperinsulinemia have been found even in children and adolescents of Asian-Indian origin [44]. These studies firmly suggest that South Asians have a special variant genotype of the thrifty gene strongly inducing insulin resistance and unusual glucose consumption. The Asian Indian phenotype—a thrifty gene seen among Pima Indians, is the most likely candidate for this special variant among the recognized thrifty genes based on the findings from several studies [36, 37]. Studies have shown that migrant Asian-Indians had a higher risk of developing diabetes and related metabolic abnormalities than other ethnic groups [37] and that the prevalence rate of diabetes and its adverse health effects has risen more rapidly among native and migrant populations in South Asia than in any other geographic region. However, another study that included 20,119 participants from South Asia revealed a considerable degree of genetic contribution to the onset of T2DM [45]. The researchers identified novel six loci (GRB14, ST6GAL1, VPS26A, HMG20A, AP3S2 and HNF4A) showing correlations with T2DM [45]. Therefore, the diabetic constitution in South Asia is suspected to be related to other genes in addition to the Asian Indian phenotype.

#### *4.1.2. Effects of family history, age and gender*

typical course of diabetes and its complications in South Asia, as explained in this section. It is evident that the prevalence rates of diabetes and its complications in South Asians are much higher than in other countries. Therefore, recognition of this critical situation is duly war-

In this section, we explore why the prevalence rate of diabetes in South Asia is so much higher than in other developed or developing countries. Among the causes, genetic factors seem to be important, as a study suggested that 30–70% of the diabetes risk could be attributed to genetic variants (SNPs of diabetic genes) [32]. Genetic variants causing diabetes have been screened since the 1990s [33]. Around 50 genetic variants, known as "obese genes" or "thrifty genes" have been identified, and the relationship between diabetes and genetic variants of β3-adrenalin receptor—a thrifty gene—have been examined in particular detail. Individuals with a variant genotype of a thrifty gene proactively store fat in the body by reducing the energy metabolism; this is beneficial in times of nutrient scarcity [34, 35]. Asian populations are much more likely to possess thrifty genotypes than Europeans. The reason for this is believed to be because South Asian populations have not had sufficient time to adapt from this variant genotype to a normal genotype, as Europeans evolved in environments where

Several studies have reported that South Asians have several risk factors for disorder of glucose consumption and insulin resistance. For instance, features of insulin resistance, such as hypertriglyceridemia, and increased abdominal or visceral fat have been seen even in nonobese Asian populations [36–38], and South Asians have more adiposity than Europeans and residents of other parts of the world with the same body weight [39, 40]. Furthermore, South Asians are more insulin resistant than other races [36, 41]. Studies conducted in India as representative South Asians have reported that Indians were at a higher risk of glucose intolerance than Europeans, even in groups with a low waist circumference [42, 43]. Insulin resistance and compensatory hyperinsulinemia have been found even in children and adolescents of Asian-Indian origin [44]. These studies firmly suggest that South Asians have a special variant genotype of the thrifty gene strongly inducing insulin resistance and unusual glucose consumption. The Asian Indian phenotype—a thrifty gene seen among Pima Indians, is the most likely candidate for this special variant among the recognized thrifty genes based on the findings from several studies [36, 37]. Studies have shown that migrant Asian-Indians had a higher risk of developing diabetes and related metabolic abnormalities than other ethnic groups [37] and that the prevalence rate of diabetes and its adverse health effects has risen more rapidly among native and migrant populations in South Asia than in any other geographic region. However, another study that included 20,119 participants from

ranted in order to mitigate the propagation of the disease condition.

**4.1. Physiological and traditional causes**

they were relatively unaffected by famine cycles [32].

*4.1.1. Genetic factors*

6 Diabetes and Its Complications

**4. Causes of the high prevalence rate of diabetes in South Asians**

Individuals' profiles are important to consider when examining the prevalence rate of diabetes [46]. The incidence of the disease in a patient's family is often involved in a given individual's risk, as the variant genotype of thrifty genes is passed down from parents to offspring. Studies comparing the effect of family with others estimated that the risk factors for diabetes in offspring with a single diabetic parent and two diabetic parents are, respectively, 3.5- and 6-fold higher than those without parental diabetes [47]. Among patterns of inheritance, diabetes and its related traits are both polygenic and heterogeneous, with multiple genes involved in different combinations [48]. However, the number of risk genes and their relative contributions are complicated and remain somewhat uncertain. A relationship is known to exist between diabetes and age, probably because the β-cells of older individuals have a reduced proliferative capacity and secreting activity, reduced expression of cell cycle activators, increased expression of cell cycle inhibitors, reduced pdx1 expression and increased amylin aggregation [49]. This decreased functional status is exacerbated in diabetic patients by increased rates of beta cell apoptosis [38]. In addition, in South Asia, elderly people tend to have a decreased muscle mass due to sedentary lifestyles [17].

In South Asians, diabetes does not always develop in the elderly, and the characteristics are remarkable. An investigation on the prevalence rate of diabetes in various age groups of South Asians showed that the diabetes population was highest among those ≥60 years of age for both males and females. However, the rate of diabetes among relatively young individuals was found to be higher in South Asians than Caucasians [37]. Furthermore, in India, the prevalence rate of diabetes peaks at 60–69 years of age [42], and Indian people develop the disease even in their youth [41]. Similar results to those in India were found in Pakistan and Sri Lanka [47]. The development of diabetes in younger generations is likely caused by changes in lifestyle brought about by urbanization [42]. The prevalence rate of diabetes (5.02%) was found to be associated with age-adjusted impaired glucose intolerance (5.27%) in a rural community in Sri Lanka [47]. Diabetes develops at any age, and the change in the prevalence over time is hypothesized to be associated with the rural to urban population shift [49].

The prevalence rate is also related to gender in South Asia. Diabetes is the second leading cause of death among South Asian women with diabetes, although it is only the ninth leading cause globally [9]. A relationship was reported between age and gender in Bangladesh diabetes patients [50]. The proportion of female diabetic patients (31.2%) was higher than that of male diabetic patients (28.5%) among subjects 31–50 years of age. Among subjects >50 years of age, the diabetic male population was 18.1% and that of the female population was 12.9%. However, below 31 years of age, only 3.3% of the male population had diabetes, whereas 6% of the female population was diabetic [51]. A study conducted in four provinces of Sri Lanka showed that the prevalence of severe obesity among males was 2.4%, whereas that among females was 8.8%. Further, the report found that, in all categories of overweight, the prevalence was greater in women than in men in all provinces [50]. Women with diabetes are also more likely to suffer a heart attack at a younger age than those without diabetes.

a result. The percentage of regular smokers in adult males of South Asia is estimated to be very high (50–60%). India is the second-largest producer and consumer of tobacco products. Many persons in India use smokeless tobacco products such as betel quid, as these are nontaxable, and those products are commonly used in rural areas of the country [58]. Concurrent use of alcohol and tobacco, which is also extremely common among South Asian populations, has a synergistic effect on the enhancement of diabetes risk [56]. With the spread of chewing tobacco, smoking is being taken up by younger and younger individuals. An investigation in 7735 British men of 40–59 years of age suggested that the consumption of tobacco, either as a smoker or user of chewing tobacco, is occurring at lower ages, and 47% of men and 14% of women who admitted to consuming tobacco had started at age 15 [57]. Reducing heavy smoking rates and the concurrent intake of alcohol are important targets for preventing diabetes and its complications among South Asians [59]. Changes in the policy and effective education programs for tobacco use in addition to alcohol use must be implemented as soon as possible.

Diabetes Mellitus in South Asia

9

http://dx.doi.org/10.5772/intechopen.76391

**4.2. Causal factors of diabetes induced by rapid globalization and development**

oped country—the prevalence rate in urban areas is similar to that in rural areas.

Afghanistan 407.00 1.02 228.59 0.40 Bangladesh 3261.80 1.20 3053.02 1.50 Bhutan 9.60 0.69 12.11 1.17 India 31384.00 0.88 30571.31 0.89 Maldives 8.00 0.88 4.75 1.51 Nepal 196.40 0.38 244.02 0.57 Pakistan 3369.70 0.94 2934.76 0.78 Sri Lanka 569.60 0.94 330.11 0.41

**Countries Female (in 1000s) Female/male (–) Urban (in 1000s) Urban/rural (–)**

Unprecedented urbanization of rural areas of South Asia is a major environmental factor involved in the increasing rate of diabetes [61]. **Table 2** shows the ratio of urban/rural localization among diabetics based on data from the International Diabetes Federation. The urban prevalence of diabetes in Sri Lanka is lower than that in rural areas [5], and similar incidences can be seen in India, Pakistan, Nepal and Afghanistan. In contrast, in countries such as Bangladesh, Bhutan and the Maldives, where urbanization has not rapidly occurred, an opposite trend is shown [5]. This is a characteristic of importance, as the prevalence rate of diabetes is generally high in urban areas (12.4%) followed by the midland (8.1%), highland (5.8%) and coastal areas (2.5%) in developing countries. To further highlight this anomaly, in Japan—which is a devel-

**Effects of gender on diabetes\* Effects of area on diabetes\*\***

*4.2.1. Urbanization*

\*

 Data from Diabetes Atlas in 2014. \*\* Data from Diabetes Atlas in 2013.

**Table 2.** Ratio of diabetes by gender and area of South Asia.

Gestational diabetes may be the main reason why there is a high prevalence rate of diabetes in women in South Asia, because the prevalence rate of GDM in South Asia is much higher than that in Europe [52, 53]. One cause of the high prevalence rate in South Asia is considered to be genetic factors. Several studies have suggested that South Asians basically have a constitution that is conducive to the development of GDM [53, 54]. Another cause is the influence of sociocultural and socioeconomic factors [55]. Weight and physical activity should be carefully controlled in order not to develop GDM before and during pregnancy. However, actions based on incorrect knowledge and bad traditional habits for pregnancy, which are taught from a person's mother, can lead to an increase in weight and a decrease in physical stress [55]. To make matters worse, GDM often causes miscarriages or birth defects, and the children born from mothers developing GDM also have a tendency to develop diabetes. Therefore, the prevention of GDM is very important to stop the passing of diabetes from mother to children and to decrease the development of diabetes among women in South Asia. It is hoped that future studies on diabetes in South Asia will focus on gestational and neonatal diabetes, and programs to prevent GDM should be established in the field at all governmental levels.

#### *4.1.3. Chronic and heavy intakes of alcohol and smoking*

Chronic drinking of large amounts of alcohol exacerbates a potential risk factor of diabetes [50]. The liver is an important organ for consuming and supplying glucose. As the chronic intake of high concentrations of ethanol induces alcoholic liver injury and inhibits the capacity to control the blood glucose level, the liver accumulates triglycerides. Such a liver condition is known as "alcoholic fatty liver." The serum levels of acetaldehyde, an intermediate metabolite of ethanol, are increased by the decrease in the detoxification capacity under conditions of alcoholic fatty liver, often severely adversely affecting the β-cells in the pancreas. Dysfunction of the liver and β-cells causes hyperglycemia, dyslipidemia and diabetes. In all South Asian countries, chronic and heavy drinking is traditionally common in poor rural regions; in addition, alcohol consumption is on the rise with rapid globalization and socioeconomic development. For instance, alcohol use among Indians has been increasing because the lifestyle patterns have been rapidly changing due to migration to urban regions and socioeconomic changes [56]. Public health policies regarding alcohol consumption are needed to stem this tide of change.

Cigarette smoking is an indirect but important risk factor for diabetes [57]. Studies have reported that a smoking habit increased the risk of developing diabetes by 44% [58], and smokers are 30–40% more likely to develop diabetes than nonsmokers [59]. Several studies have attempted to elucidate the relationship. Smoking reduces the insulin sensitivity because nicotine included in cigarettes has the ability to inhibit insulin secretion via neuronal nicotinic acetylcholine receptors. Furthermore, smoking damages cells by increasing the amount of reactive oxygen [60], and inflammation occurs at the damaged portion, causing swelling of cells. Smoking is also associated with an increased risk of abdominal obesity [39]. These harmful effects cause metabolic disorders of glucose and lipids and increase the risk of diabetes as a result. The percentage of regular smokers in adult males of South Asia is estimated to be very high (50–60%). India is the second-largest producer and consumer of tobacco products. Many persons in India use smokeless tobacco products such as betel quid, as these are nontaxable, and those products are commonly used in rural areas of the country [58]. Concurrent use of alcohol and tobacco, which is also extremely common among South Asian populations, has a synergistic effect on the enhancement of diabetes risk [56]. With the spread of chewing tobacco, smoking is being taken up by younger and younger individuals. An investigation in 7735 British men of 40–59 years of age suggested that the consumption of tobacco, either as a smoker or user of chewing tobacco, is occurring at lower ages, and 47% of men and 14% of women who admitted to consuming tobacco had started at age 15 [57]. Reducing heavy smoking rates and the concurrent intake of alcohol are important targets for preventing diabetes and its complications among South Asians [59]. Changes in the policy and effective education programs for tobacco use in addition to alcohol use must be implemented as soon as possible.

#### **4.2. Causal factors of diabetes induced by rapid globalization and development**

#### *4.2.1. Urbanization*

females was 8.8%. Further, the report found that, in all categories of overweight, the prevalence was greater in women than in men in all provinces [50]. Women with diabetes are also

Gestational diabetes may be the main reason why there is a high prevalence rate of diabetes in women in South Asia, because the prevalence rate of GDM in South Asia is much higher than that in Europe [52, 53]. One cause of the high prevalence rate in South Asia is considered to be genetic factors. Several studies have suggested that South Asians basically have a constitution that is conducive to the development of GDM [53, 54]. Another cause is the influence of sociocultural and socioeconomic factors [55]. Weight and physical activity should be carefully controlled in order not to develop GDM before and during pregnancy. However, actions based on incorrect knowledge and bad traditional habits for pregnancy, which are taught from a person's mother, can lead to an increase in weight and a decrease in physical stress [55]. To make matters worse, GDM often causes miscarriages or birth defects, and the children born from mothers developing GDM also have a tendency to develop diabetes. Therefore, the prevention of GDM is very important to stop the passing of diabetes from mother to children and to decrease the development of diabetes among women in South Asia. It is hoped that future studies on diabetes in South Asia will focus on gestational and neonatal diabetes, and programs to prevent GDM should be established in the field at all governmental levels.

Chronic drinking of large amounts of alcohol exacerbates a potential risk factor of diabetes [50]. The liver is an important organ for consuming and supplying glucose. As the chronic intake of high concentrations of ethanol induces alcoholic liver injury and inhibits the capacity to control the blood glucose level, the liver accumulates triglycerides. Such a liver condition is known as "alcoholic fatty liver." The serum levels of acetaldehyde, an intermediate metabolite of ethanol, are increased by the decrease in the detoxification capacity under conditions of alcoholic fatty liver, often severely adversely affecting the β-cells in the pancreas. Dysfunction of the liver and β-cells causes hyperglycemia, dyslipidemia and diabetes. In all South Asian countries, chronic and heavy drinking is traditionally common in poor rural regions; in addition, alcohol consumption is on the rise with rapid globalization and socioeconomic development. For instance, alcohol use among Indians has been increasing because the lifestyle patterns have been rapidly changing due to migration to urban regions and socioeconomic changes [56]. Public health policies regarding alcohol consumption are needed to

Cigarette smoking is an indirect but important risk factor for diabetes [57]. Studies have reported that a smoking habit increased the risk of developing diabetes by 44% [58], and smokers are 30–40% more likely to develop diabetes than nonsmokers [59]. Several studies have attempted to elucidate the relationship. Smoking reduces the insulin sensitivity because nicotine included in cigarettes has the ability to inhibit insulin secretion via neuronal nicotinic acetylcholine receptors. Furthermore, smoking damages cells by increasing the amount of reactive oxygen [60], and inflammation occurs at the damaged portion, causing swelling of cells. Smoking is also associated with an increased risk of abdominal obesity [39]. These harmful effects cause metabolic disorders of glucose and lipids and increase the risk of diabetes as

more likely to suffer a heart attack at a younger age than those without diabetes.

*4.1.3. Chronic and heavy intakes of alcohol and smoking*

stem this tide of change.

8 Diabetes and Its Complications

Unprecedented urbanization of rural areas of South Asia is a major environmental factor involved in the increasing rate of diabetes [61]. **Table 2** shows the ratio of urban/rural localization among diabetics based on data from the International Diabetes Federation. The urban prevalence of diabetes in Sri Lanka is lower than that in rural areas [5], and similar incidences can be seen in India, Pakistan, Nepal and Afghanistan. In contrast, in countries such as Bangladesh, Bhutan and the Maldives, where urbanization has not rapidly occurred, an opposite trend is shown [5]. This is a characteristic of importance, as the prevalence rate of diabetes is generally high in urban areas (12.4%) followed by the midland (8.1%), highland (5.8%) and coastal areas (2.5%) in developing countries. To further highlight this anomaly, in Japan—which is a developed country—the prevalence rate in urban areas is similar to that in rural areas.


**Table 2.** Ratio of diabetes by gender and area of South Asia.

Rapid urbanization gives important variation of rural area where agriculture had been the principle profession [9]. Urbanization has reduced the physical activity and altered dietary habits by changing the lifestyle among residents of rural areas through means such as increased mechanization of the agriculture industry, automation of daily activities, popularization of television and increased computer usage, which has accordingly increased the proportion of obese persons [9, 10]. Studies have shown that the prevalence rate of diabetic complications is associated with wealth/income, education and office-based occupations in South Asia [62]. Socially deprived urban South Asian communities have a lower prevalence of diabetes and obesity than developed countries [1], and a study performed in Sri Lanka reported that the majority of patients developing diabetic neuropathy resided in rural areas (75.3%) with a monthly income exceeding Sri Lankan Rs. 12,000 (87.6%) [31]. The inhabitants of South Asian countries who reside in rural areas and show a low prevalence of diabetes are involved in agriculture and engage in intense physical labor. These results suggest that the affluence accompanying urbanization leads to a luxurious—and by extension—more sedentary lifestyle, thereby increasing the rate of diabetes [63].

The amounts of fats and carbohydrates as well as the total calories strongly influence the rate of obesity, and the body mass index (BMI), glycemic index (GI) and glycemic load (GL) can be used as indices to estimate the amounts of fats and carbohydrate. Many nations in South Asia tend to have relatively high-GI and high-GL diets. For example, white rice, which is a daily staple of the South Asian diet, has a higher GI than whole-grain rice. A recent meta-analysis found that a single increment in white rice serving per day increased the risk of diabetes by 11% [71]. Furthermore, large portion sizes and predominantly starch-based diets in South Asians, which correspond to a high GL, are also associated with obesity. Reducing the carbohydrate portion sizes and increasing the portion of vegetables is necessary to reduce the

Diabetes Mellitus in South Asia

11

http://dx.doi.org/10.5772/intechopen.76391

Poor lifestyles, such as a short sleeping time, watching TV for a prolonged period and physical inactivity brought about by urbanization, may function as factors exacerbating and triggering the development of diabetes. The sleep duration among Asians is relatively short. In a meta-analysis of data from 23 countries, adolescents in Asia were sleeping 40–60 min less each night than Americans and 60–120 min less each night than Europeans [73]. Some studies have suggested that this short duration of sleep in Asians was associated with an increased risk of diabetes, childhood obesity and cardiometabolic abnormalities [73, 74]. As sleep-disordered breathing induces a twofold increase in the risk of diabetes [73], a short duration of sleep may

Inactive behaviors (watching TV or playing on a PC for a prolonged period and sedentary careers) may also be associated with diabetes in South Asians. Prolonged stints of watching TV are independent of the metabolic activity for obesity, but wasting so much time with this behavior tends to be associated with an unhealthy diet, including increased consumption of snacks, sugary beverages and fast food [38]. Furthermore, this lifestyle is associated with physical inactivity due to a decrease in the metabolic capacity when performing such daily work. Therefore, watching TV for a prolonged period consequently increases the prevalence rate of obesity and diabetes. In addition, many studies in South Asians have revealed a rapid shift to careers in the service sector due to economic growth and the advent of new technologies. This has led to careers involving long durations of sitting, thereby resulting in a marked decline in physical activity [38]. People in a high socioeconomic class are more prone to developing diabetes than those in lower economic classes. Of special note, a study in adults in Sri

Lanka revealed a strong association between physical inactivity and diabetes [75].

Education about diabetes is much more lacking among South Asians than in Europeans, and this low consciousness of diabetes has consequently contributed to an increase in the rate of diabetes in South Asians. A study conducted in Bangladesh found that individuals with more education had a 1.67-fold lower risk of developing diabetes than those with little or no education [75]. In that study, employees who had often been educated about diabetes had a lower probability of having diabetes themselves than unemployed individuals [75]. Another study in Sri Lankans showed that a higher educational level may be associated with better diabetes-related outcomes [70]. Therefore, education starting from elementary school may be an effective and practical

diabetes risk, as high-GI and high-GL diets contribute to obesity [71, 72].

*4.2.3. Increase in undesirable lifestyles and a shortage of education programs*

induce a condition similar to that of sleep-disordered breathing.

#### *4.2.2. Increase in the rate of obesity due to changes in the diet*

Obesity is a major determinant of T2DM. Many recent studies elucidated the mechanism underlying the development in T2DM. White adipocytes secrete adipokines, such as leptin, adiponectin and TNF-α. Leptin and adiponectin enhance the capacity of glucose consumption by increasing the noradrenalin secretion, but TNF-α inhibits it via the inhibition of insulin receptor and transport of GLUT4 [64]. As the secretion of leptin and adiponectin is decreased and the secretion of TNF-α is increased in white adipose tissues highly accumulating triglyceride, the glucose intake is inhibited [65]. Furthermore, the pressure on blood vessels induced by hypertrophic white adipose tissues causes an inflammatory response, and the enhanced concentration of free fatty acids in the blood by obesity causes the dysfunction of mitochondria in muscle cells and β-cells of the pancreas [66, 67]. These harmful effects induce disorder of glucose consumption and insulin resistance, thereby resulting in the development of T2DM.

Urbanization in South Asia is a major contributory factor to obesity [68, 69]. Investigations conducted among rural communities in Sri Lanka showed a strong relationship between diabetes and excess body weight, and the prevalence rate of obesity in diabetic patients (21%) was higher (*P* < 0.05) than in nondiabetic individuals (10.5%) [70]. Obesity is no longer a disease of affluent and therefore majority of the populations in South Asia in the wake of rapid changes in lifestyle among more rural populations [58]. As previously stated, migration toward rural areas of South Asia induced dramatic changes to the diet within a decade. Traditional dietary patterns are now being lost, and a significant transition to energy-rich diets is occurring in South Asia. The diet has shifted from relatively monotonous food products like indigenous staple grains or starchy roots, locally grown legumes, other vegetables and fruits, along with limited foods of animal origin (except for prosperous subpopulations), to more varied diets that include more preprocessed foods with higher fat and lower carbohydrate content, more foods of animal origin, edible oils and more added sugars, especially in the form of processed drinks and foods, and often more alcohol. These changes in diet have caused a rapid increase in the obese population of South Asia.

The amounts of fats and carbohydrates as well as the total calories strongly influence the rate of obesity, and the body mass index (BMI), glycemic index (GI) and glycemic load (GL) can be used as indices to estimate the amounts of fats and carbohydrate. Many nations in South Asia tend to have relatively high-GI and high-GL diets. For example, white rice, which is a daily staple of the South Asian diet, has a higher GI than whole-grain rice. A recent meta-analysis found that a single increment in white rice serving per day increased the risk of diabetes by 11% [71]. Furthermore, large portion sizes and predominantly starch-based diets in South Asians, which correspond to a high GL, are also associated with obesity. Reducing the carbohydrate portion sizes and increasing the portion of vegetables is necessary to reduce the diabetes risk, as high-GI and high-GL diets contribute to obesity [71, 72].

#### *4.2.3. Increase in undesirable lifestyles and a shortage of education programs*

Rapid urbanization gives important variation of rural area where agriculture had been the principle profession [9]. Urbanization has reduced the physical activity and altered dietary habits by changing the lifestyle among residents of rural areas through means such as increased mechanization of the agriculture industry, automation of daily activities, popularization of television and increased computer usage, which has accordingly increased the proportion of obese persons [9, 10]. Studies have shown that the prevalence rate of diabetic complications is associated with wealth/income, education and office-based occupations in South Asia [62]. Socially deprived urban South Asian communities have a lower prevalence of diabetes and obesity than developed countries [1], and a study performed in Sri Lanka reported that the majority of patients developing diabetic neuropathy resided in rural areas (75.3%) with a monthly income exceeding Sri Lankan Rs. 12,000 (87.6%) [31]. The inhabitants of South Asian countries who reside in rural areas and show a low prevalence of diabetes are involved in agriculture and engage in intense physical labor. These results suggest that the affluence accompanying urbanization leads to a luxurious—and by extension—more seden-

Obesity is a major determinant of T2DM. Many recent studies elucidated the mechanism underlying the development in T2DM. White adipocytes secrete adipokines, such as leptin, adiponectin and TNF-α. Leptin and adiponectin enhance the capacity of glucose consumption by increasing the noradrenalin secretion, but TNF-α inhibits it via the inhibition of insulin receptor and transport of GLUT4 [64]. As the secretion of leptin and adiponectin is decreased and the secretion of TNF-α is increased in white adipose tissues highly accumulating triglyceride, the glucose intake is inhibited [65]. Furthermore, the pressure on blood vessels induced by hypertrophic white adipose tissues causes an inflammatory response, and the enhanced concentration of free fatty acids in the blood by obesity causes the dysfunction of mitochondria in muscle cells and β-cells of the pancreas [66, 67]. These harmful effects induce disorder of glucose consumption and insulin resistance, thereby resulting in the development of T2DM. Urbanization in South Asia is a major contributory factor to obesity [68, 69]. Investigations conducted among rural communities in Sri Lanka showed a strong relationship between diabetes and excess body weight, and the prevalence rate of obesity in diabetic patients (21%) was higher (*P* < 0.05) than in nondiabetic individuals (10.5%) [70]. Obesity is no longer a disease of affluent and therefore majority of the populations in South Asia in the wake of rapid changes in lifestyle among more rural populations [58]. As previously stated, migration toward rural areas of South Asia induced dramatic changes to the diet within a decade. Traditional dietary patterns are now being lost, and a significant transition to energy-rich diets is occurring in South Asia. The diet has shifted from relatively monotonous food products like indigenous staple grains or starchy roots, locally grown legumes, other vegetables and fruits, along with limited foods of animal origin (except for prosperous subpopulations), to more varied diets that include more preprocessed foods with higher fat and lower carbohydrate content, more foods of animal origin, edible oils and more added sugars, especially in the form of processed drinks and foods, and often more alcohol. These changes in diet have caused a rapid increase

tary lifestyle, thereby increasing the rate of diabetes [63].

10 Diabetes and Its Complications

*4.2.2. Increase in the rate of obesity due to changes in the diet*

in the obese population of South Asia.

Poor lifestyles, such as a short sleeping time, watching TV for a prolonged period and physical inactivity brought about by urbanization, may function as factors exacerbating and triggering the development of diabetes. The sleep duration among Asians is relatively short. In a meta-analysis of data from 23 countries, adolescents in Asia were sleeping 40–60 min less each night than Americans and 60–120 min less each night than Europeans [73]. Some studies have suggested that this short duration of sleep in Asians was associated with an increased risk of diabetes, childhood obesity and cardiometabolic abnormalities [73, 74]. As sleep-disordered breathing induces a twofold increase in the risk of diabetes [73], a short duration of sleep may induce a condition similar to that of sleep-disordered breathing.

Inactive behaviors (watching TV or playing on a PC for a prolonged period and sedentary careers) may also be associated with diabetes in South Asians. Prolonged stints of watching TV are independent of the metabolic activity for obesity, but wasting so much time with this behavior tends to be associated with an unhealthy diet, including increased consumption of snacks, sugary beverages and fast food [38]. Furthermore, this lifestyle is associated with physical inactivity due to a decrease in the metabolic capacity when performing such daily work. Therefore, watching TV for a prolonged period consequently increases the prevalence rate of obesity and diabetes. In addition, many studies in South Asians have revealed a rapid shift to careers in the service sector due to economic growth and the advent of new technologies. This has led to careers involving long durations of sitting, thereby resulting in a marked decline in physical activity [38]. People in a high socioeconomic class are more prone to developing diabetes than those in lower economic classes. Of special note, a study in adults in Sri Lanka revealed a strong association between physical inactivity and diabetes [75].

Education about diabetes is much more lacking among South Asians than in Europeans, and this low consciousness of diabetes has consequently contributed to an increase in the rate of diabetes in South Asians. A study conducted in Bangladesh found that individuals with more education had a 1.67-fold lower risk of developing diabetes than those with little or no education [75]. In that study, employees who had often been educated about diabetes had a lower probability of having diabetes themselves than unemployed individuals [75]. Another study in Sri Lankans showed that a higher educational level may be associated with better diabetes-related outcomes [70]. Therefore, education starting from elementary school may be an effective and practical way of reducing the rate of diabetes. The World Diabetes Foundation has already implemented prevention programs at the national level to educate students in urban and semi-urban areas in South Asian countries about the risk of diabetes, in view of these shortcomings [76].

rate of diabetes. The first strategy involves the induction of uncoupling protein 1 (UCP1) by changing the diet and lifestyle. UCP1, which is expressed only in brown adipocytes, plays a role in nonshivering heat generation using the proton potential of the inner membrane of mitochondria. Through the effects of UCP1, fatty acid is effectively metabolized to compensate for the loss of energy. Recently, the effects of UCP1 on glucose and insulin resistance were examined using fatty mouse and UCP1 transgenic mouse models [77–79]. The results of those studies suggest that increasing the concentration of UCP1 is the most effective way to rescue subjects with preliminary T2DM. The induction of UCP1 is relatively easy because muscle cells and white adipocytes can be differentiated to brown adipocyte by the stimulation of cool temperatures and exercise [80, 81] or by consuming herbal and/or complementary medicines [66]. We therefore think that the induction of brown adipocytes is the most inexpensive and effective way of preventing the development of diabetes at the early stage in South Asia.

Diabetes Mellitus in South Asia

13

http://dx.doi.org/10.5772/intechopen.76391

The second strategy involves qualitative improvements in the diet by proactively consuming functional compounds or food products containing antidiabetic bioactives. Many effective compounds for protecting against obesity have been identified. For example, consuming fish instead of meat is good for protecting against obesity because DHA contained in fish can reduce fat and cholesterol. Proactively consuming food containing polyphenols, such as green tea, soybean products and berries, and carnitine, such as fish [82–84], is also effective for similar reasons. Superfoods that contain high levels of these effective compounds and functional foods with artificially enhanced levels have been enthusiastically studied, and many inexpensive functional foods and supplements are now available in developed countries [85, 86]. The proactive consumption of superfoods and functional foods through the daily diet without expensive drugs is extremely effective for protecting against obesity and diabetes.

The final and most important strategy involves changing the consensus. If most South Asians with obese constitutions continue their bad habits, such as chronic heavy smoking and drinking and consuming high-calorie and oily foods, the rapid increase in the prevalence rate of diabetes cannot be effectively curbed. In Japan, the consensus regarding obesity and metabolic syndrome has recently been enhanced by a trend toward anti-obesity and education via TV and books; in this way, the rising tide of obesity is being stemmed little by little. This is a strategy which could be easily implemented in South Asia as well. Therefore, revising the consensus can be effective, even in South Asians. In a case report from Ballabgarh, India, a five-step model (identify the problem, understand the problem, evaluate feasible and costeffective intervention) is addressed to the issue [87], but statistics clearly display that such efforts are not sufficient, and further education toward diabetes and national strategies and interventions to protect against obesity and diabetes should be implemented immediately.

We focused on the issue of the recent increase in the diabetes prevalence in South Asia and described the results consequently obtained in associated studies. First, we investigated the prevalence of diabetes and its complications in South Asia. Existing studies and statistics suggest that the prevalence was much higher in this region than in other developed and developing countries

**6. Conclusion**

**Figure 2** shows a schematic illustration of the characteristics of diabetes in South Asia described in this chapter. The causes underlying the high prevalence of diabetes in South Asians can be distilled down to four main factors. First, South Asians have the thrifty gene derived from Asian Indian populations that induces insulin resistance and disorder of glucose consumption; they therefore develop a T2DM constitution. Second, obese populations are increasing due to dietary changes and a decrease in physical activity in the wake of remarkable economic progress, which causes T2DM. Third, traditional bad habits such as chronic heavy smoking and drinking, which cause T1DM and T2DM, are increasingly being adopted due to increased income caused by economic progress. Fourth, the recognition to diabetes is poor because of a lack of relevant policies and the education system.

**Figure 2.** Causes of diabetes in South Asia and suggestions for their prevention.
