Energy-restricted diets based on a distinct food selection affecting the glycemic index induce different weight loss and oxidative response.

BACKGROUND & AIMS Low glycemic index (GI) based diets could influence the accompanying physiological adaptations to energy restriction in the treatment of obesity. It was aimed to investigate the effects of two energy-restricted diets with different food distribution and GI values on weight loss and energy metabolism in the nutritional treatment of obesity. SUBJECTS AND METHODS Participants (n=32; BMI: 32.5+/-4.3 kg/m(2)) were randomly assigned to follow two energy-restricted diets with higher-GI or lower-GI for 8 weeks. The energy restriction was -30% in relation to energy expenditure. Anthropometry, energy expenditure and mitochondrial oxidation were assessed at baseline and at the endpoint of the intervention. Body weight was also measured one year after the treatment. The work was approved by the ethical committees of the University of Navarra (54/2006). RESULTS Volunteers consuming the lower-GI diet showed a significantly higher weight loss than their counterparts (-5.3+/-2.6% vs -7.5+/-2.9%; p=0.032), although the decrease in resting energy expenditure (REE) was similar between groups (p=0.783). Mitochondrial oxidation was significantly affected by the type of diet (p=0.001), being activated after the lower-GI treatment (p=0.022). Interestingly, one year after the nutritional intervention weight regain was only statistically significant in the higher-GI group (p=0.033). CONCLUSIONS Lower-GI energy-restricted diets achieved through a specific differential food selection can improve the energy adaptations during obesity treatment, favouring weight loss and probably weight maintenance compared with higher-GI hypocaloric diets.