Researchers estimate that poor diet contributed to more than 14.1 million cases of type 2 diabetes in 2018.
This represents more than 70% of new diagnoses across the world, the study suggests.
The analysis, which looked at data from 1990 and 2018, provides insight into which dietary factors are driving the type 2 diabetes burden by world region.
The findings are based on a research model of dietary intake in 184 countries, developed by researchers at the Friedman School of Nutrition Science and Policy at Tufts University in America.
Of the 11 dietary factors considered, three had a big contribution to the rising global incidence of type 2 diabetes, the scientists suggest.
These were insufficient intake of whole grains like oats and whole wheat, excesses of refined rice and wheat, and the overconsumption of processed meat.
According to the findings, factors such as drinking too much fruit juice and not eating enough non-starchy vegetables, nuts, or seeds, had less of an impact on new cases of the disease.
Senior author Dariush Mozaffarian, who is Jean Mayer professor of nutrition and dean for policy at the Friedman School, said: “Our study suggests poor carbohydrate quality is a leading driver of diet-attributable type 2 diabetes globally, and with important variation by nation and over time.
“These new findings reveal critical areas for national and global focus to improve nutrition and reduce devastating burdens of diabetes.”
Type 2 diabetes is characterised by the resistance of the body’s cells to insulin.
Of the 184 countries included in the Nature Medicine study, all saw an increase in type 2 diabetes cases between 1990 and 2018.
The researchers based their model on information from the Global Dietary Database (an ongoing global project to collect data on dietary intakes of major foods) along with population data from multiple sources, global type 2 diabetes incidence estimates, and data on how food choices impact people living with obesity and type 2 diabetes.
The analysis revealed that poor diet is causing a larger proportion of total type 2 diabetes incidence in men versus women, in younger versus older adults, and in urban versus rural residents at the global level.
Central and Eastern Europe and Central Asia, particularly in Poland and Russia, where diets tend to be rich in red meat, processed meat, and potatoes, had the greatest number of type 2 diabetes cases linked to diet.
Incidence was also high in Latin America and the Caribbean, especially in Colombia and Mexico, which was credited to high consumption of sugary drinks, processed meat, and low intake of whole grains.
Regions where diet had less of an impact on type 2 diabetes cases included South Asia and Sub-Saharan Africa.
The largest increases in type 2 diabetes due to poor diet between 1990 and 2018, however, were observed in Sub-Saharan Africa.
First author Meghan O’Hearn, who conducted this research while a PhD candidate at the Friedman School, said: “Left unchecked and with incidence only projected to rise, type 2 diabetes will continue to impact population health, economic productivity, health care system capacity, and drive heath inequities worldwide.
“These findings can help inform nutritional priorities for clinicians, policymakers, and private sector actors as they encourage healthier dietary choices that address this global epidemic.”