One explanation relies on a trio of social forces: aging population, urbanization, and economic growth. According to this model, as people move to cities, they give up manual labor and adopt a more sedentary lifestyle. This, combined with longer lives and increases in income that allow people to buy more food, may drive the increasing rate of obesity around the world. While obesity and diabetes remain distinct problems -- not all obese people develop diabetes and not all diabetics have weight problems -- they so closely interrelate that researchers frequently lump them together.

Yet, models based on these social factors have significantly underestimated the spread of diabetes in the developing world over the past 20 years. A group of researchers affiliated with the London School of Hygiene and Tropical Medicine and the World Health Organization set out to explain this gap. Their findings, published in the journal Public Health Nutrition, compares 173 countries' diabetes prevalence, food consumption and socioeconomic situations.

As expected, increased urbanization, economic development, sedentary lifestyle, and total food available corresponded to higher rates of diabetes. However, after adjusting this data to control for differences in refined sugar consumption, these correlations disappeared. This suggests that rather than an inherent connection between urbanization and diabetes, for instance, the correlation between the two appears because life in cities exposes people to more sugar. A growing body of public health research on high-income countries supports this conclusion that eating more processed foods high in sugar increases the risk of diabetes. Additionally, research on refined sugars indicates that their metabolism in our bodies may cause changes in insulin response that contribute to diabetes regardless of obesity. The populations examined in this study mirror this physiological phenomenon: after adjusting for obesity, the correlation between sugar and diabetes remains. Amidst the complex solutions offered, it appears that expanded consumption of sugar propels the pandemic of diabetes.

While affluence and urbanization may not cause diabetes, economics dictate a country's exposure to refined sugars and processed foods. In this 47-year study, GDP increases in low- and middle-income countries were positively correlated with the amount of sugar available to the average person. At first glance, it appears that with more money people began to buy processed foods they could not afford before. But it's really a byproduct of economic growth that may be responsible for increasingly sugary diets. According to the data, the growing share of an average person's diet from sugar was tied not to GDP, but to increases in food imports. Dr. Sanjay Basu, lead author of the study, explains that the opening of international trade markets that comes with economic growth allows for the influx of cheap, processed foods. Soda and sweets from abroad offer cheap replacements for a traditional diet and put the populace at risk for diabetes.

Still, it's worth remembering that correlative studies only suggest trends and relationships between diabetes and diet, and population data cannot prove with scientific accuracy that sugar causes diabetes.

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