Obesity and type 2 diabetes are increasing in rural and urban regions of South Asia including India. Pattern of fat deposition in abdomen, ectopic fat deposition (liver, pancreas) and also low lean mass are contributory to early-onset insulin resistance, dysmetabolic state and diabetes in Asian Indians. These metabolic perturbations are further exacerbated by changing lifestyle, diet urbanization, and mechanization. Important dietary imbalances include increasing use of oils containing high amount of trans fatty acids and saturated fats (partially hydrogenated vegetable oil, palmolein oil) use of deep frying method and reheating of oils for cooking, high intake of saturated fats, sugar and refined carbohydrates, low intake of protein, fiber and increasing intake of processed foods. Although dietary intervention trials are few; the data show that improving quality of carbohydrates (more complex carbohydrates), improving fat quality (more monounsaturated fatty acids and omega 3 polyunsaturated fatty acids) and increasing protein intake could improve blood glucose, serum insulin, lipids, inflammatory markers and hepatic fat, but more studies are needed. Finally, regulatory framework must be tightened to impose taxes on sugar-sweetened beverages, oils such as palmolein, and dietary fats and limit trans fats.
Obesity and metabolic syndrome, not known to be prevalent previously in South Asians due to generally labour intensive lifestyle and frugal diets, are increasing in urban and semi-urban regions of South Asia.1, 2 These are prime determinants of type 2 diabetes, and cardiovascular disease.3 In general, despite some differences, similar secular trends have been seen in all South Asian countries, including India, Afghanistan, Bangladesh, Bhutan, Pakistan, Maldives, Sri Lanka and Nepal.4
In this review, we intend to discuss impact of obesity patterns, changing dietary practices and cooking methods, nutrient manipulations and intervention in context of obesity, insulin resistance, metabolic syndrome and cardiovascular risk factors in Asian Indians, with some reference to South Asians.
A literature search was conducted of studies on obesity specifically abdominal obesity and trends in changing dietary pattern with respect to carbohydrates, fats and protein from 1966 to January 2017 in the medical search database of PubMed (National Library of Medicine, Bethesda, MD, USA) and Google Scholar. We carried out a literature search using the terms ‘obesity, abdominal obesity’, ‘trends in the consumption of: carbohydrates, fats, protein’, ‘consumption of processed food’, ‘dietary interventions’, ‘sugar tax’ and ‘fat tax’ in the Indian context. The Data have also been extracted from references known to authors, and from following websites of the World Health Organization (WHO), National Sample Survey Organization (NSSO India), the Food and Agricultural Organization (FAO), and industries related to sugar and edible oil production.
Abdominal obesity, ectopic fat and diabetes
Increasing trend of obesity, abdominal obesity and metabolic syndrome is particularly worrisome since Asian Indians develop diabetes and atherogenic dyslipidemia at lower levels of body mass index and waist circumference.5, 6 These data have necessitated lower cutoffs for definitions of overweight and obesity vs whites.7 Onset of dyslipidemia and metabolic syndrome are early contributing factors to onset of diabetes.8
It is important to understand pattern of fat deposition and lean mass in various parts of body of South Asians, since these impact metabolism (Table 1). The data show a number of differences in comparison to white Caucasians. While intra-abdominal visceral adipose tissue is higher in South Asians,9 specifically in those with diabetes,10 these observations were not shown in women residing in USA.11 In particular, there is excess of truncal and abdominal subcutaneous adiposity. Specifically, deep subcutaneous abdominal adipose tissue (deep SCAT) may have more metabolic activity, and its expansion may adversely affect insulin resistance and cardiovascular risk12 in South Asians who have thicker abdominal subcutaneous adipose tissue,13 with excess deep SCAT. Further, hepatic fat accumulation is ~2-folds higher in the Asian Indians compared with all other ethnic groups, associated with heightened insulin resistance. Such excess hepatic fat is also associated with increased pancreatic volume (surrogate of ‘fatty pancreas’). Specifically, in non-obese patients with diabetes, pancreatic volume and liver span (a surrogate of excess fat deposition in liver) were increased by 26.6 and 10.8%, respectively, as compared to non-obese non-diabetic Asian Indians.14 Interestingly, increased fat deposition in liver and pancreas in Asian Indians, in a preliminary cross-sectional data, have potential of predicting diabetes.15 Fatty pancreas appears to be a particularly interesting pathological entity, and may have potential to reflect both insulin resistance and insulin secretory defect, and needs further research in this ethnic group. Interestingly, abdominal subcutaneous adipocyte area is increased in South Asians.13 Adjustment for adipocyte area attenuated the ethnic differences in insulin and adiponectin levels and liver fat in South Asians. Further, the subcutaneous adipocyte size was inversely correlated to glucose disposal rate in South Asians, independent of intra-peritoneal fat.16 These authors opined that heightened insulin resistance in South Asians appears to be related more to increased truncal subcutaneous fat and adipose tissue dysfunction than to excess intra-abdominal visceral fat.
A less investigated issue is skeletal muscle mass and its impact on metabolism in South Asians. The comparative data suggest lower skeletal muscle mass in South Asians vs white Caucasians;13 possible explanations being low physical activity, low-protein diets and genetic make-up in the former.17 In particular, thigh muscle area is lower in South Asians, in both genders, and associated with diabetes and coronary heart disease.18 In a study done on limited sample of South Indians, 39.5% of patients had pre-sarcopenia independently associated with diabetes.19 Another facet of muscle composition is accumulation of intra-myocellular triglycerides, which are higher in Asian Indians with type 2 diabetes,20 but did not have significant correlation with insulin sensitivity as compared to white Europeans.21 This issue of ‘fatty muscles’ and low skeletal muscle mass, in South Asians, needs more research with focus on protein intake and genetic determinants, including myostatin gene.17
Much of the above discussion must be taken in context of nutrition and physical activity. Various issues pertaining to nutrition, oil intake and dietary habits vis-à-vis obesity and type 2 diabetes will be discussed in subsequent sections.
Nutrition transition in India: impact of open market economy
Rapid urbanization, mechanization, changing lifestyle and trade liberalization over past three decades has led to changes in dietary consumption patterns, including processed foods in India. Foreign direct investment (FDI) has become increasingly important since the mid-1980s, enabling production, distribution and consumption of highly processed foods, and has attracted foreign investment.22 In India, there is increasing demand for processed food products since they can be prepared easily and are reasonably priced.23 The national policy aims to increase the level of food processing from 10 (2010) to 25% in 15 years and this market is growing at 14% per annum.24, 25
Fats and edible cooking oils: trends in consumption
National Sample Survey Organization (NSSO) reports (55th (1999–2000), 61st (2004–2005), 66th(2009–2010) and 68th (2011–2012) rounds26, 27, 28, 29 show an unmistakable rising trend in the per capita calorie and fat intake, not only at national level but in every major state, both in urban and rural populations (Figure 1). There is an increasing trend for import of oils during last decade which includes palm/palmolein (78%) followed by soybean (10%) and sunflower oil (9%) (Table 2).30, 31 The share of oils are as follows; raw oil (35%), refined oil (55%) and vanaspati (partially hydrogenated vegetable oil, (PHVO)) (10%).32
Cooking oils are very important ingredient of cooking in South Asia. Most of the Indian snacks and sweets made and consumed on any special occasion or festival are laden with ghee (clarified butter) or vegetable oils.
Per capita edible oil consumption in India is increasing by 3–4% per annum, being ~14.4 kg in 2013–2014. Recently, sunflower, soybean and palm oils have been used increasingly. Palm and soybean oils account for almost half of the total edible oil consumption followed by mustard and groundnut oils in India (Figure 2).26 It is important to note that consumption of refined palm/palmolein as well as its blending with other oils has escalated over the years in India. In particular, these oils are extensively used in hotels, restaurants and in preparation of wide varieties of food products mainly because it is 20–30% cheaper than other vegetable oils. It is important to mention here that Palm oil contains high amount (49 g) of saturated fat/100 gm of oil.30 Consumption of specific oils varies according to geographical regions in India. In particular, Ghee (clarified butter made from animal milk) is an important ingredient for cooking but is also used for various religious rituals in north India. Further, the following consumption patterns are seen; mustard oil and Vanaspati in East and parts of North India, groundnut oil in west (Gujarat) and Central India, sesame oil (til oil) in state of Rajasthan in North and, and Coconut oil in South India (Kerala).33
Cooking methods: impact on oil composition
The traditional cooking practice adopted in India involves the cooks (home, restaurants) and roadside food vendors who heat and reheat fats and oils in a large karahi (a deep, thick, circular pot used for open-air deep frying) at high temperatures and almost always reuse of such oils to cut costs.34 These processes promote neo-formed contaminants (NFCs) such as advanced glycation end-products (AGEs) and trans-fatty acids (TFAs).35, 36 TFAs are also formed during the frying, during partial hydrogenation of vegetable oils and in small amounts during refining of vegetable oils.37 The formation of TFAs during food frying is increased in high temperature frying and reuse of same oils.38 It is proposed that high heat/frying as cooking methods may be important contributor to CVD in South Asians.39 Bhardwaj et al34 researched formation of TFAs when oils/fats as used in Indian cooking, are constantly heated at high temperature and underwent deep frying. These procedures resulted in high levels of TFAs and SFAs at the cost of cis-unsaturated fatty acids. Further, TFA formation after heating/frying was even observed for three oils that had undetectable amounts of TFA (refined soybean oil, refined groundnut oil and refined olive oil) before heating. Increased consumption of TFAs may occur with increasing use of PHVO, repeated heating of fats/oils for preparation of popular and frequently consumed traditional fried snacks.40
Increasing intake of refined carbohydrates, non-home-cooked foods and processed foods
Consumption of refined carbohydrates is high in Asians Indians/South Asians. Noodles, vermicelli and refined flour breads, kulchas (a type of leavened bread made from refined wheat flour), pao bread (a small loaf of bread made from refined wheat flour) are being increasingly consumed instead of whole wheat flour chapatis (unleavened flat bread made from whole wheat flour), millet chapatis and chilas (pancake made from gram flour). Refined carbohydrates are mainly rapidly digesting starches, which lead to higher postprandial glucose peak, a reported problem with Asian Indians.
The NSSO lists processed foods into two categories: those served in restaurants, dhabas (roadside restaurants), snack bars and so on, and those which are bought and consumed at home. Taken together, beverages and processed foods accounted for 7.9% (1.75 USD) of consumer expenditure in rural India and 9% (3.66 USD) in urban India.
The data from 68th round of National Sample Survey Organization (NSSO)26 show that there is a substantial increase in the consumption of ‘misc. foods’ (which includes processed foods), in both rural (2.4–7.04%) and urban areas (5.6–8.6%) from 1993 to 2012. Further, the snacks (mostly potato based) market in India is worth 220 million USD with rapid annual growth.41 The National level data show that consumption of salted refreshments (savory) has increased from 0.04 kg per capita per month to 15.08 kg per capita per month in 2012.26 Importantly, carbonated drinks sales in India is US$ 1.5 billion, while the fruit juice and fruit juice-based drink sales are US$ 0.25 billion. Growing at a rate of 25%, the fruit-drinks category is one of the fastest growing segments in the beverages market.41
Traditionally a higher priority has always been given to fresh foods rather than the purchase of convenience foods in India, but these are changing now.42 In a study conducted in four cities of India in 2011, about 88% of the children felt that home-cooked food was healthy but 40% of the children felt that home-cooked food was ‘old fashioned’.43 Importantly, younger Indians are more willing to opt for novel food products and they have an innate tendency of perceiving imported foods to be of ‘high quality’ in comparison to locally produced products.43, 44 NSSO data show a clear increase in the percent share of calories from ‘misc. foods’ from 2.32 and 5.52% in 2000 to 8.61 and 9.01% in 2012 in rural and urban areas, respectively. Interestingly, along with an increased consumption of modern processed foods from transnational food companies (TFCs), which are high in carbohydrates, fats, sugars and salt, India is also creating processed versions of traditional dishes; ready-to-eat dals (soups prepared from pulses), parathas (shallow fried unleavened flat breads of wheat flour), pulaos (rice cooked with vegetables and spices) and so on.)
Sugar intake in Asian Indians, obesity and diabetes
Sugar intake leads to the several adverse metabolic events; accumulation of body fat and intra-abdominal fat, excess liver fat, increased insulin resistance, hypertriglyceridemia, increased free fatty acids, hyperuricemia and diabetes.45, 46 It is important to note that India is the second largest (after Brazil) producer and largest consumer of sugar globally.47 Further, India is the largest producer of khandsari and gur (other forms of locally produced ‘traditional’ sugar in India).48 Interestingly, while intake of these ‘traditional sugars’ has declined, intake of sugar from sugar-sweetened beverages (SSBs) has increased. It is interesting to note that when consumption from jaggery/khandsari and SSBs are added to that of white sugar,49, 50, 51, 52 the ‘total’ sugar intake in Indians is around 25.17 Kg per annum, exceeding the per capita global consumption of 23.7 kg per annum.53 Finally, consumption of traditional sweets, which have high concentration of sugar and fat, is high in India.
Specifically, increased risks for obesity, diabetes, and heart disease is closely associated with consumption of sugar-sweetened beverages (SSBs).54 Since 1998, sales of SSBs have increased by 13% per year in India and these are easily available in rural and urban areas.52
Protein intake in Asian Indians and sarcopenia
Protein intake in Asian Indians has been more discussed in context of under-nutrition and poor growth, rather than obesity and diabetes. National data show relatively lower intake of protein in Asian Indians (10.8% in rural and 10.9% in urban population) vs north Americans in USA (nearly 16%).55, 56 Protein intake has not changed much over past one decade in both rural and urban India and there is hardly any difference in the protein intake of rural and urban populations (Figure 1).
Importantly, when protein digestibility-corrected amino acid score (PDCAAS), using lysine as the first limiting amino acid, is considered, all population segments in India, particularly rural and tribal, have an inadequate quality of their protein intake.57 Besides these data, research studies are few. In a study done on 1236 subjects (607 males, 629 females) aged 13–25 years from schools and colleges of New Delhi, intake of protein was 11% of energy intake, while a small study showed higher protein intake (14% males and 12% females) in immigrant Asian Indians in Michigan, USA.58 Low protein intake may be more marked in vegetarians.59
Overall protein intake and its quality are lower in Asian Indians and may impact the skeletal muscle mass and sarcopenia.
Evidence of benefits of nutrient manipulation for South Asians
To curb rising prevalence of obesity and type 2 diabetes in Asian Indians, simple and cost-effective strategies are needed. It is important, therefore, to focus on interventions that can improve insulin sensitivity and decrease adiposity, and also target ectopic fat (including liver fat). Low intake of monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs) and fiber, and high intake of saturated fats, TFAs and carbohydrates60 are some of the imbalances in nutrition of Asian Indians/South Asians, and these could be targeted for metabolic benefits. Intervention trials with nutrition are few, pertinent ones are summarized below.
While there are studies which show that decreasing carbohydrates in diets may help in reducing weight and improving insulin sensitivity, it is not always possible in South Asians, because of their tendency to eat largely carbohydrate based diets. In STARCH (Study To Assess the dietaRy CarboHydrate) study, it was observed that carbohydrates constitute 64.1% of the total energy in Indian patients with type 2 diabetes.61 Cereals are staple foods and contribute about two-thirds of the total carbohydrates consumed.62 It may, however, be feasible to alter quality of carbohydrates so as to have metabolic benefits. Mohan et al63 in a randomized cross over trial on 15 non-diabetic Asian Indians, compared white rice with brown rice and brown rice with legumes. The percentage difference in 5-day average incremental area under the curve was 19.8% lower in the brown rice group than in the white rice group (P=0.004). Brown rice with legumes intake further decreased the glycemic response (22.9% lower compared with white rice, P=0.02). The authors concluded that 24-h glucose and fasting insulin responses among overweight Asian Indians can be reduced by consumption of brown rice in place of white rice.63 Given importance of carbohydrates in diets consumed by Asian Indians, more research is needed.
There is a paucity of intervention trials on protein intake, muscle strength and diabetes in Asian Indians. In view of low efficiency protein of vegetarian diet in Asian Indians, trials using higher dietary protein, and in particular for lysine and leucine are needed. In a 8-week trial in healthy men, high lysine diets (80 mg/kg per day) had a positive effect, albeit small, on muscle strength.64 In a well-characterized birth cohort (n=1446, 32% females, born near Hyderabad, India, in 29 villages from 1987 to 1990), adult lean body mass (LBM) and muscle was assessed after long-term nutrition program. Multivariable regression analyses showed that adult LBM and muscle strength has positive association with physical activity levels and energy intake. This study could not detect a ‘programming’ effect of early nutrition supplementation on adult LBM and muscle strength.65 In a randomized trial, 60 sedentary osteoporotic women (mean age 54.55 years) were assigned to three groups: soy + exercise group, soy isolate protein (Group A), and control group. Significant muscle performance changes, after intervention were evident in 60 osteoporotic sedentary postmenopausal women.66 Although high protein intake was associated with diabetes in a study with limited number of immigrant Asian Indians, the findings need to be substantiated.67
Increasing protein in diets may also lead to weight loss with multiple metabolic benefits. In a randomized controlled parallel arm open label study on obese Asian Indians (n=122), intervention with diet high in protein (29% of total energy) and low in carbohydrates (47%) against a control diet of 60% carbohydrates and 15% protein over a period of 3 months has shown significant reduction in body weight, waist circumference, blood pressure, fasting blood glucose, serum insulin, lipids, hs-CRP and liver aminotransferases.68 Possible mechanisms of weight loss with high-protein diets include increased thermogenesis and satiety.69, 70 Satiety is influenced by the postprandial amino acid concentrations, through stimulation of gastrointestinal hormones cholecystokinin, Peptide YY (PYY) and glucagon-like peptide-1 (GLP-1).71, 72, 73
Dietary intake of MUFAs increase insulin sensitivity while regulating postprandial glucose levels, minimizing increases in blood TC and LDL-C and promoting elevated HDL-C levels.74 In a randomized controlled parallel arm open label study in Asian Indians with the metabolic syndrome (n=60), intervention high-MUFA diet, which included unsalted pistachio nuts (20% of total energy) for 6 months resulted in beneficial effects on waist circumference, fasting blood glucose, lipid parameters, adiponectin, free fatty acids, hs-CRP and oxidative stress.75
In another study in Asian Indian subjects with type 2 diabetes (n=63), supplementation with almonds (20% of total energy) for 6 months led to significant reduction in waist circumference, waist-to-height ratio, TC, LDL-C, serum triglycerides, glycosylated hemoglobin and hs-CRP.76
In randomized controlled trial, interventions with the olive or canola cooking oils (20 g per day) vs oils low in MUFAs for 6 months in Asian Indians with non-alcoholic fatty liver (n=93) improved grading of fatty liver, fasting blood glucose, serum triglycerides high-density lipoprotein cholesterol and serum insulin was reported.77
Such interventions with MUFA-rich diets are important for South Asians because of their impact on abdominal obesity, metabolic syndrome and subclinical inflammation. Clearly, more experiments with dietary MUFAs are needed in Asian Indians.
Omega 3 polyunsaturated fatty acids
It has been hypothesized the prevalence of metabolic abnormalities among Asian Indians may be related to an imbalance in dietary PUFAs intake,78 specifically the higher intake of n-6 PUFAs in combination with the lower intake of long-chain (LC) n-3 PUFAs. However, only a few intervention studies with n-3 PUFAs are available for South Asians. In this context, Indu & Ghafoorunissa showed supplementation of oral intake of n-3 PUFAs on serum triglycerides and decrease platelet aggregation in a limited number of subjects.79 A randomized, double-blind, placebo-controlled, parallel, fish-oil intervention study by Lovegrove et al.,80 where 44 Europeans and 40 Indo-Indian Sikhs were randomly assigned to receive either 4.0 g fish oil (1.5 g eicosapentaenoic acid (EPA) and 1.0 g docosahexaenoic acid (DHA)) or 4.0 g olive oil (control) daily for 12 weeks showed a significant decrease in plasma triacylglycerol, plasma apolipoprotein B-48 and platelet phospholipid arachidonic acid concentrations in Indo-Asians with fish oil intervention but insulin sensitivity remained unchanged.
These interventions highlight the need for dietary modifications for Asian Indians who have the higher propensity for developing metabolic perturbations. The potentially important dietary intervention among Asian Indians are listed in Table 3.
Regulation of harmful foods in south Asians: possible benefits
Increasing taxation on sugar, SSBs and edible fats are part of public health nutrition approach to curb obesity and diabetes.81 A strategic controlling of price can be instrumental in lowering the consumption of unhealthy foods which can minimize the negative effects of the nutrition transition.82 A study by Ford et al83 in the US showed that price increases of 10%, 15, and 20% on SSBs were associated with fewer purchases of juice drinks. Basu et al.51 suggest that a 20% soda tax may lead to a reduction of 3% in obesity (or prevent 11.2 million new cases), and a 1.6% decrease in prevalence of T2DM (or prevent 400 000 cases), over the decade 2014–2023 in India. These compelling data should lead to reformulation of strategies for curbing non-communicable diseases by enhancing taxation on SSBs.
As stated previously, consumption of palm oil is high in India. Basu et al30 in a modeling study proposed that 20% tax on palm oil purchases in India was projected to avert approximately 363 000 deaths from cardiovascular disease (myocardial infarction and stroke; 1.3% reduction in cardiovascular deaths) over the period 2014–23.
Trans fatty acids
Standards for TFAs in India are being debated since 2004 by the Union Ministry of Health and Family Welfare. In 2009, Center for Science and Environment (CSE) had released a study that found that the quantity of trans fats in all vanaspati brands was 5–12 times higher than the standards for Denmark, that is, 2% of the total fat content. In 2010, the National Institute of Nutrition (NIN) conducted a national consultation which concluded that the levels of trans fats in vanaspati should be below 10%. The Food Safety and Standards Authority of India (FSSAI) had drafted regulations for TFA limits at 10 per cent (by weight) in 2010, and proposed to bring it to five per cent in three years. However, it still is not implemented.
Importantly, labelling for TFA poses a major challenge in India Considering the negative effects of TFA on health (specifically in Asian Indians with high propensity to develop CVD) and increase in formation of TFA on repeated use of oils, it should be mandatory to carry out laboratory analysis of the TFA content of each batch of fats/oils used for frying. Finally, stringent policies regarding quality of edible fats/oils should be developed for India.34
Recently, in July, 2016 a ‘fat’ tax (tax on burgers, pizzas and other junk food) of 14.5% is introduced in the state of Kerala, India. It is estimated that tax would add 100 million rupees (1.53 million USD) annually to state’s funds and also make people more conscious of their food choices.84
Other governmental interventions
Policy evidence from existing food tax implementation suggests that taxes need to be paralleled by subsidies on healthier foods like fruits and vegetables and other interventions to encourage healthy eating.85 Such dual methods would be helpful for in changing consumer behavior and improved nutrition outcomes.
Dietary pattern is rapidly changing in India owing to changing lifestyle, and is contributing to increasing numbers of obesity, diabetes and cardiovascular disease. The National data show increasing consumption of sugar, fats and processed foods in India. There is strong need to curtail the consumption of these foods by implementation of policies such as increased taxation. Also strategies like improving the carbohydrate quality, correct choice of cooking oils, increasing protein intake, increasing MUFA and n-3 fatty acids in the diet, while cutting down intakes of sugar and SSBs and saturated and trans fats could be helpful in preventing abdominal adiposity, ectopic fat deposition, hyperglycemia, and atherosclerosis.