Using individual food glycaemic index (GI) values to predict the GI of a meal in healthy people and comparing this estimated GI with the GI obtained from the people consuming the meal

The glycaemic index (GI) of a meal is not normally measured, it is calculated according to a formula using the GIs of the individual foods contributing to the meal. It has been suggested that this predictive method is inaccurate. We therefore designed a study to test how the GIs of three meals, obtained using the predictive formula, compared with the direct determination of the GIs of the meals. The three meals all comprised a portion of chicken, sweet potato, peas, carrots and sauce having a combined carbohydrate content of 25 g. Another 25 g of carbohydrate was provided by including in the meal either potato, rice or pasta.The meals were approximately equicaloric (2100 kJ) and contained approximately 55% carbohydrate, 27% fat and 18% protein. Each meal was consumed comfortably within 15 minutes. Each participant consumed each of the meals with at least two days between successive tests. Participants were given a standard protocol to follow including an overnight fast.