Dear Dietitian

Why do my blood glucose levels increase after a 98% fat-free food?

I recently had a 98% fat-free milkshake from a popular takeaway store and was surprised to see it increased my blood glucose levels to unacceptable levels. Why is this?

A fat free claim only tells us how much fat is in a food; it fails to indicate anything else about that food.

The amount of total carbohydrate is the most important guide to determining the effect on your blood glucose levels. The total carbohydrate is made up of added sugar and natural sugars and starches in the food.

The serving size is also important. A small milkshake will not cause your blood glucose to rise to the extent a large milkshake will.

Before blaming one particular food it is useful to consider other foods that may have also contributed to the increased blood glucose levels. For example, did you eat chips or a burger as well? What were your blood glucose levels beforehand?