Recent animal research provides compelling evidence that high GI carbohydrate is associated with increased risk of obesity. In human trials it is typically difficult to separate the effect from GI and other potentially confounding factors such as fibre content, palatability and compliance.
In the study (Pawlak et al, 2004), male rats were split into a high and low GI group over 18 weeks while mean bodyweight was maintained. Rats fed the high GI diet were 71% fatter and 8% less lean than the low GI group. Postmeal glycemia and insulin levels were significantly higher and plasma triglycerides were three-fold greater in the high GI fed rats. Furthermore, pancreatic islet cells suffered ‘severely disorganised architecture and extensive fibrosis’. The evidence in this study showed that continued consumption of high glycemic index carbohydrate would likely have led to the development of severe metabolic abnormalities.