Low-GI diet doesn't curb appetite

Lowering the glycaemic index (GI) or carbohydrate content of mixed meals reduces blood glucose and insulin levels throughout the day without influencing satiety, new research shows.

"Most studies of glycaemic index or glycaemic load have looked at individual foods and some have argued that combining individual foods into a meal may not have the same effect," said Dr Frank L Greenway from Louisiana State University System in Baton Rouge, whose findings were published online in Diabetes Care.

"This study gives further support in that reducing glycaemic index and glycaemic load have a beneficial effect on blood glucose and insulin sensitivity even in the context of meals throughout the day, the way that people normally eat their food," he said.

How the study was done

Dr Greenway and colleagues tested postprandial glucose and insulin response, as well as subjective hunger and satiety, in 26 otherwise healthy overweight or obese adults. Each participant received four diets (high GI, high carbohydrate; high GI, low carbohydrate; low GI, high carbohydrate; low GI, low carbohydrate) in random order with a three-day washout between diets.

Mean glucose and insulin area-under-the-curve (AUC) values were significantly higher for the high-GI, high-carb diet than for all other diets (p<0.001).

The biggest difference was seen for the low-GI, low-carb diet, with a 42% reduction in serum glucose and a 29% reduction in serum insulin. For the high-GI, low-carb diet, the numbers were 24% and 20%, respectively.

There were no differences among the four diets in subjective measures of hunger, fullness, or satiety throughout the course of the day.

As for energy levels and mood, participants rated their levels of weariness higher and felt that doing anything took more effort when they were on the low-GI, low-carb diet than with the high-GI, high-carb diet.

Calmness ratings were highest with the low-GI, high-carb diet, while sadness ratings were highest with the high GI, low-carb diet.

"Not only has reducing glycaemic load and glycaemic index been suggested to be helpful in treating diabetes and impaired glucose tolerance, but it has been suggested by some to be a useful strategy to treat obesity," Dr Greenway explained.

"These people have theorised that the reduction in the rise and fall of glucose and the reduction in the insulin excursions would help to reduce hunger and aid weight loss. We tested this hypothesis and found that although reducing glycaemic load and glycaemic index has a beneficial effect on glucose and insulin, it does not reduce appetite and, by implication, would have little benefit in treating obesity."

(Reuters, July 2012)

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