Type 2 diabetes (T2D) is highly prevalent in Mexico, especially in acculturated populations of indigenous people. Based on studies in US Pima, indigenous people of North America seem to be highly susceptible to T2D. Physical (in)activity and diet are the two most important lifestyle determinants in the development and prevention of T2D.

Physical activity is likely to influence the development or prevention of T2D in individuals with impaired glucose tolerance (IGT), but not in individuals with impaired fasting glycaemia (IFG). This difference is caused by the positive effect on peripheral insulin resistance – a characteristic of IGT – by physical activity, but not on hepatic insulin resistance – a characteristic of IFG. The Tarahumara – an indigenous people of northern Mexico – is known to have high physical activity level. Since this group is slowly being acculturated, it will be possible to measure a wide variety of physical activity ranging from the “traditional” (high activity level) to the “transitional” (low activity level) groups. This will enable us to measure the effect of different levels of physical activity volume and intensity on glucose tolerance in Tarahumara.

We therefore propose a study in which 260 (based on statistical power calculations) adult Tarahumara of both sexes, aged 20-60 years, participate in an epidemiological study focusing on physical activity and glucose tolerance, lipid profile, blood pressure and anthropometric measures. The metabolic and anthropometric changes between three distinct “activity” seasons over the course of a year within the “traditional” and “transitional” groups as well as between the two groups will determine the effect of physical activity on these changes.  The results are expected to be applicable to public health measures (prevention, treatment of diabetes) not only in the Tarahumara, but also in other indigenous people and Latin American people in lifestyle transition.

Sub-study: Exercise, Cardiac and Kidney Function Project

Prior to and up to 48 hours following an extreme running competition 10 Tarahumara men and 10 Tarahumara women will be tested for exercise-induced cardiomyopathy using plasma biomarkers (10 ml of blood each time blood is being drawn) as well as using a standard echocardiographic scanning protocol for functional and structural cardiac response (done by trained cardiac nurse or medical doctor).

Energy expenditure during the extreme running competition using combined accelerometry and heart rate measurement will also be collected (methodology as described above under free-living physical activity). Standard biological background data including cardio-respiratory fitness, blood pressure, standard anthropometrics, blood glucose, haemoglobin, and 12-lead ECG will be measured as well.

All variables will be measured/collected according to standard procedures and taking into account culturally sensitive issues, i.e. female staff doing anthropometric measurements on female study participants.