In the randomized maintenance phase, which was initiated immediately after participants completed the weight-loss phase, participants were assigned to one of five diets, in a two-by-two factorial design: a diet that was low in protein (13% of total energy consumed) with a low glycemic index, a diet that was low in protein with a high glycemic index, a diet that was high in protein (25% of total energy consumed) with a low glycemic index, a high-protein and high-glycemic-index diet, or a control diet. The control diet, which followed dietary guidelines in each participating country, had a moderate protein content and did not include instructions to participants with respect to the glycemic index.
Study participants were instructed to maintain their weight loss during this phase, although further weight reduction was allowed. All five diets were designed to have a moderate fat content (25 to 30% of total energy consumed) with no restrictions on energy intake (i.e., ad libitum diets), in order to test the ability of the diets to regulate appetite and body weight. We targeted a difference of 15 glycemic-index units between the high-glycemic-index diets and the low-glycemic-index diets and a difference of 12% of total energy consumed from protein between the high-protein diets and the low-protein diets. Visits for dietary counseling took place every other week during the first 6 weeks and monthly thereafter. The families were provided with recipes, cooking and behavioral advice, and a point-based teaching system to achieve the targeted macronutrient compositions.13 (link)In Maastricht and Copenhagen (“shop centers”), the families received dietary instruction plus free foods from the laboratory shop for 26 weeks so that we could assess the effect that the provision of food would have on adherence. In the other six centers (“instruction centers”), the families were provided with dietary instruction only.14 (link),15 (link) Local sponsors made financial contributions to the shop centers, and food manufacturers provided a number of foods free of charge. The local sponsors and food manufacturers had no influence on the selection of foods found in the two shops, nor were they involved in designing the study or in analyzing and interpreting data.
Study participants were instructed to maintain their weight loss during this phase, although further weight reduction was allowed. All five diets were designed to have a moderate fat content (25 to 30% of total energy consumed) with no restrictions on energy intake (i.e., ad libitum diets), in order to test the ability of the diets to regulate appetite and body weight. We targeted a difference of 15 glycemic-index units between the high-glycemic-index diets and the low-glycemic-index diets and a difference of 12% of total energy consumed from protein between the high-protein diets and the low-protein diets. Visits for dietary counseling took place every other week during the first 6 weeks and monthly thereafter. The families were provided with recipes, cooking and behavioral advice, and a point-based teaching system to achieve the targeted macronutrient compositions.13 (link)In Maastricht and Copenhagen (“shop centers”), the families received dietary instruction plus free foods from the laboratory shop for 26 weeks so that we could assess the effect that the provision of food would have on adherence. In the other six centers (“instruction centers”), the families were provided with dietary instruction only.14 (link),15 (link) Local sponsors made financial contributions to the shop centers, and food manufacturers provided a number of foods free of charge. The local sponsors and food manufacturers had no influence on the selection of foods found in the two shops, nor were they involved in designing the study or in analyzing and interpreting data.
