Among the modifiable risk factors for type 2 DM, overweight and obesity are the most well documented. The standard measure of body weight in population studies is body mass index (BMI). According to the 2004 Canadian Community Health Survey, the prevalence of obesity (defined using BMI) was higher among Indigenous Canadians (37.8 %) when compared to non-Indigenous Canadians (22.6 %) [61]. The prevalence of obesity was also higher among Indigenous children and youth (15.8 %), when compared to their non-Indigenous counterparts [61, 62].

When determining the prevalence of overweight and obesity in Indigenous peoples, it is salient to consider that the body dimensions of this group, and the Inuit population in particular, are different than other populations [63]. The Inuit are shorter in height and have shorter legs [63]. As a result, in order to improve the assessment of obesity in Inuit people, measures of body fat distribution, such as waist circumference, waist-to-height, and waist-to-hip ratio, should be employed [64–66]. In fact, a meta-analysis of over 300,000 individuals from different populations around the world found that waist-to-hip ratio was a better predictor than waist circumference and BMI for diabetes risk [66]. In a study on First Nations in Ontario, the 10-year cumulative incidence of diabetes was associated with high adiposity (defined as higher body mass index, percent body fat, waist circumference, or waist-to-height ratio) [27].

Cigarette smoking has been associated with an increased risk of type 2 DM in a meta-analysis of 25 prospective cohort studies [67]. According to the meta-analysis, the risk of type 2 DM was greater for those who smoked >20 cigarettes a day than those who smoked <20 cigarettes a day [67]. Smoking prevalence is high in Indigenous populations and has been associated with complications of type 2 DM [44]. According to national data from the 2009–2010 Canadian Community Health Survey, the prevalence rates of self-reported smoking among Indigenous peoples aged 18 years and older were twofold higher than the rates of the non-Indigenous population [21]. Moreover, rates of daily tobacco smoking in Indigenous peoples were also 2.2–2.8 times higher than non-Indigenous people [21]. According to the 2012 Aboriginal People’s Survey, 52 % of Inuit aged 15 years and older smoked cigarettes daily, and another 9 % were occasional smokers [68].

In a study on First Nations in Ontario, former smoking was found to be associated with low beta-cell function, and current smoking was associated with high beta-cell function, independent of diabetes. Additionally, the association of smoking with insulin resistance varied depending on glycemic status [69]. In another First Nations population, smoking was found to increase incident diabetes risk in carriers of the HNF1A G319S allele. After stratification by baseline smoking status, HNF1A G319S carriers who were active smokers had increased risk of developing diabetes [70].

Research on the association of diet with type 2 DM has received considerable attention. Numerous dietary factors such as coffee, fiber, whole grains, and dairy products have been shown to have a protective effect on type 2 DM risk [71–74]. While some dietary factors including sugar-sweetened beverages and high consumption of fat have been associated with an increased risk for type 2 DM [75, 76]. Additionally, specific nutrients such as vitamin D have recently been investigated for their protective effects against the development of type 2 DM [77].

The nutritional habits of Indigenous peoples are of significant interest in the context of the management and prevention of type 2 DM [78]. Until relatively recently, Indigenous people of Canada were nomadic hunters and gatherers who had a traditional diet which consisted of large and small animals and birds (including the flesh and organs of moose, caribou, rabbit, ducks, geese, etc.), freshwater fish, marine fish and mammals, and some plant foods and, most notably, berries [79, 80]. In addition, the Iroquoian peoples of the Great Lakes and St. Lawrence River region farmed corn, beans, squash, and other crops. A significant body of research has documented a marked nutrition transition among Indigenous Canadians, in which the nutritional profile of Indigenous Canadians has changed from a traditional diet to a “market-foods” diet that is characterized by a higher intake in fat (especially saturated fat) and simple and high GI carbohydrates and low fiber [78, 81–84].

While the consumption of traditional foods has declined in general, Indigenous communities in some regions, most notably in the Northwest Territories and Yukon, have maintained a reasonably high degree of traditional food consumption [81, 85, 86]. Traditional food consumption is associated with beneficial impact on micronutrient intake. For instance, days with traditional food consumption are characterized by increased intakes of vitamins D, E, and B6, magnesium, and selenium. In addition, days when Indigenous participants consumed traditional food were characterized by higher intakes of energy as protein, whereas days when traditional food was not consumed were associated with a higher percentage of energy as carbohydrate, sucrose, and saturated and polyunsaturated fatty acids [81]. The potential benefits of high-fiber, high-fruit/vegetable/whole grain, low-fat, low-protein diets in the prevention of type DM among Indigenous Canadians have been studied [36, 38, 84, 87], and the findings have been largely consistent with those from other populations [88–90]. With regard to traditional foods, the consumption of seal oil and salmon has been found to be associated with a reduced risk of glucose intolerance in Indigenous people of Alaska [91]. In addition, in Cree from James Bay, higher traditional food consumption was associated with increased n-3 fatty acids [92]. Overall, however, very limited data are available regarding traditional food consumption and health outcomes among Indigenous peoples.

The transition to a market-foods diet has been accompanied by increasing prevalence of type 2 DM in Indigenous populations [10, 25]. A study in a First Nations community in Ontario found a high intake of total and saturated fat, and a diet high in GI foods was more common in people under 50 years of age, where rates of diabetes are showing their sharpest increase [83]. In another study in the same population, data was obtained using food frequency questionnaires to determine dietary patterns in the community. The intake of foods in the “junk foods” (chips/pop/candy/canned meat) category and fat (especially lard, consumed or used in preparation) category was associated with an increased risk of type 2 DM [84]. Similarly, a junk food dietary pattern (high-fat and high-sugar foods) identified in the Cree from Northern Quebec was associated with increased diabetes risk [92].

Another key public health nutrition problem affecting Indigenous communities is food insecurity. The prevalence of both individual and household food insecurity is much higher for Indigenous people compared to non-Indigenous people, with data from a national survey showing that 33 % of off-reserve Indigenous Canadians were food insecure compared to 9 % of non-Indigenous Canadians [93, 94]. After controlling for differences in household sociodemographic risk factors (including household income, highest level of education in household, household type, number of children, etc.), Indigenous households had two to six times greater odds for food insecurity compared to non-Indigenous households [93, 94]. In a recent national survey on Inuit, 41 % of Inuit aged 15 and older lived in households that experienced food insecurity [68].

Barriers to food security in Indigenous populations include income inadequacy and environmental pollution related to the impact of climate change on traditional food systems [86, 95]. A large number of Indigenous households rely on social assistance for income [93]. In fact, over 66 % of Indigenous households who received social assistance were food insecure [94]. In a study of access to traditional and market foods in 44 Indigenous communities across Arctic Canada, regional variation affected price and ability to purchase adequate food, with between 40 and 70 % of people saying they could afford enough food [96]. Additionally, Indigenous people reported inadequate access to fishing and hunting equipment, and 46 % of people could not afford to go hunting or fishing [96]. Changes in the local environment including changes in water levels have affected harvesting and traditional food acquirement in Indigenous communities [97]. Environmental contaminants in Indigenous traditional food resources such as heavy metals, radionuclides, and organochlorines put the health of Indigenous people at an increased risk [98]. In order to eradicate food insecurity among off-reserve Indigenous populations, government interventions must first address the great burden of poverty in this group by increasing income and social assistance funding for families [93, 95]. Overall, the considerable barriers to both traditional food and healthy market-food access discussed above have significant public health implications for both managing and preventing the type 2 DM epidemic currently being experienced by Indigenous communities in Canada.

Engaging in physical activity has been well established to improve blood glucose control and has been identified as an important determinant in the prevention and management of type 2 DM [99–101]. A recent meta-analysis found that moderate intensity physical activity including brisk walking was negatively associated with the risk of type 2 DM [102].

Historically, Indigenous peoples engaged in activities such as hunting, fishing, and trapping to obtain sustenance [103]. However, as mentioned earlier, because of the nutrition transition, traditional activities are less prevalent, and this change has had a negative impact on the level of physical activity among Indigenous peoples and increasing the risk of type 2 DM and its complications [103]. According to a study in a First Nations community in Ontario, both physical activity and fitness were associated with lower insulin concentrations, suggesting that physical activity/fitness may be beneficial to the prevention of type 2 DM [104]. Television viewing was associated with childhood obesity in Mohawk children of Kahnawake [105]. Similarly, in First Nations people aged 10–19 years, 5 or more hours of television viewing/day was associated with a significantly higher risk of overweight than 2 or less hours of television viewing/day [36].

High rates of youth-onset obesity and type 2 DM in Indigenous communities suggest that risk factors are operating very early in life, perhaps even in the intrauterine period. Recent research arising from the Developmental Origins of Health and Disease (DOHaD) paradigm has highlighted the importance to chronic disease etiology of a number of factors that have a significant importance in the context of type 2 DM in Indigenous Canadians [106], including high birth weight, gestational diabetes, and suboptimal breastfeeding.

High birth weight can have both immediate- and longer-term health consequences on infants, including shoulder dystocia, and an increased risk of type 2 DM [107, 108]. High birth weight appears to be closely associated with maternal diabetes and overweight. Consequently, as the prevalence of maternal obesity and gestational diabetes mellitus (GDM) continues to increase, higher birth weight babies will become increasingly prevalent as well [109].

There have been consistent observations of high birth weight in Indigenous Canadian babies [110, 111]. The prevalence of high birth weight in Cree was 34.3 % compared to 11 % in their non-Indigenous counterparts [112]. In a recent study on First Nations women in Northern and in Southern Quebec, First Nations women were more likely to have high birth weight babies than non-Indigenous women [113]. Similarly, a study reporting singleton births from Cree women living in rural or remote communities in Northern Quebec found prevalence rates of 2.4 % for low birth weight and 36.5 % for high birth weight. In the same study, infants who weighed >4500 g had a 14 % higher prevalence of birth injuries and were more likely born to women with GDM [114]. Another study on First Nations in Quebec reported a significant association between macrosomia and postnatal mortality [115].

Notwithstanding the importance of risk factors that occur at the level of the individual, it is increasingly being recognized that factors that characterize the local or broader social, environmental, and/or geographical environment are playing a critical role in the etiology of type 2 DM in Indigenous communities in Canada. These environmental risk factors for type 2 DM have emerged largely from historic policies of colonization unique to the Indigenous context [116]. In particular, the health and social conditions of Indigenous peoples vary significantly depending on residence on-reserve versus off-reserve and in rural versus urban areas [117]. Living in remote or rural areas may lead to limited opportunities for education and employment and reduced access to a safe and healthy food supply [20, 117]. Geographic and language barriers may also result in reduced access to health-care services [118]. As well, there is limited availability of culturally appropriate services in Indigenous communities [20, 119]. These limitations may potentially affect the prevalence and distribution of type 2 DM in Indigenous peoples by affecting the level of care and treatment available for type 2 DM and its complications [117].