Is GI A Stand-In For Something Else?
The health benefits of a low glycemic index diet are also being questioned. Several studies have shown that switching to a low GI diet improves insulin sensitivity in individuals with type 2 diabetes, but the effect is small compared to that of exercise. And a recent study found that 18 months on a low GI diet had no effect on weight loss in Brazilian women compared to a high GI diet. What’s more, when confounding variables such as fiber intake are removed, the glycemic index of one’s habitual diet is a poor predictor of overweight, diabetes and cardiovascular disease. In other words, eating a high GI diet is no more likely than eating a low GI diet to make you fat or diabetic or to cause a heart attack.
Increasingly, experts believe that it’s not the glycemic effect of certain foods that makes them healthy but their fiber and perhaps also their antioxidant content. For example, a large, recent Dutch study found no association between glycemic load (which factors in both the glycemic index and the total amount of carbohydrate) in the individual diet and various cardiovascular disease risk factors. There was a link between the glycemic index of the individual diet and these risk factors, but the study also found that a lower GI diet was typically achieved through all-around healthier food choices (such as more fruit and fewer sweets).
Conventional wisdom holds that a high GI diet increases metabolic disease risk by causing repeated glucose and insulin spikes. But this study suggests that the truth is less complicated. High GI diets simply tend to contain lots of high-calorie foods that make people fat. Thus, the glycemic index is really just a stand-in for other food qualities that affect metabolic disease risk: specifically, calorie density and satiety. Foods that contribute to lowering the GI of one’s diet, such as fruit and vegetables, provide more satiety per calorie, whereas foods that contribute to increasing the GI of the diet, such as sweets, are more calorie-dense and less filling.