Effects of different protein content and glycemic index of ad libitum diets on risk factors for diabetes in overweight adults after weight loss: the DIOGenes multicentre, randomised, dietary intervention trial

Aims/hypothesis: Diets which differ in protein and glycemic index (GI) may distinctively contribute to body weight control and metabolic consequences, especially those related to insulin sensitivity. Methods: In DIOGenes, overweight/obese adults in 8 European countries who lost ≥ 8% of initial body-weight following a low calorie diet (LCD) were subsequently randomly assigned into five ad libitum interventional groups during 6 months: Low Protein [LP]/Low GI [LGI]; LP/High GI [HGI]; High Protein [HP]/LGI; HP/HGI and a healthy conventional control diet. Body weight, fasting insulin as well as an oral glucose tolerance test (OGTT), HOMA-IR, adiponectin and fructosamine levels were determined at the three time points. Results: The LCD period was initiated by 932 adults, 773 were randomised to the 5 diets and 548 completed the intervention. The HP and LGI diets were related to weight-loss management and to a lower drop-out rate. The LP/HGI diet induced a greater increase in HOMA-IR during the 6 month period. The HP and LGI diets decreased HOMA-IR (p<0.001) in those patients with the highest weight-loss (≥10% of initial body-weight). The LGI diets also lead to a decrease in fructosamine levels (p<0.05), and plasma insulin response was lower in the HP/LGI after 60 and 90 min of the OGTT at the end of the 6months intervention (p<0.05) as compared to others. Conclusion/Interpretation: An increase in dietary protein and a reduction in GI content over a 6-month ad libitum dietary intervention produced better compliance and favorable effects on glycaemic control and insulin sensitivity in overweight/obese subjects after an initial body-weight loss. The study was registered with ClinicalTrials.gov, number NCT00390637.