Epidemiological surveys show a large variation of type 2 diabetes (DT2) prevalence from one country to another, suggesting ethnic discrepancies in insulin sensitivity. Many data seem to confirm this hypothesis. We will show them while concentrating on data provided by surveys performed in French-speaking countries. The mechanisms of the ethnic differences in insulin sensitivity are unclear and further insights are needed. More than genetic factors, environmental factors appear to be involved in the occurence of insulin resistance and DT2. The epidemic nature of obesity and subsequent DT2 in the world urges health authorities in each country to raise campaigns to promote changes in life style and nutritional habits before the announced pandemy of DT2 becomes reality.