The American Journal of Clinical Nutrition · 15 authors, 11 centres
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This 12-week randomized trial in overweight adults found that a 20% energy-restricted diet led to significant weight loss and reduced adipose tissue. Postprandial metabolic challenges (OGTT) were more sensitive than fasting markers for detecting improvements in insulin action markers like leucine and glutamate.
Participants were randomized to a weight loss group with a 20% energy restriction or a weight-maintenance group. Body composition was measured by MRI, and metabolic responses were assessed via oral glucose tolerance (OGTT) and mixed-meal tolerance tests before and after the intervention. The weight loss group achieved a significant mean weight loss of -5.6 kg, with reductions in total, regional, and liver ectopic fat. The central result was that postprandial amino acid markers of insulin resistance, specifically leucine and glutamate, decreased in the OGTT after weight loss. A key finding was that dietary challenges increased the sensitivity for detecting metabolic improvements compared to fasting samples. Limitations include the inclusion of generally healthy volunteers with normoglycemia, which may limit the magnitude of metabolic improvements, and the reliance on self-reported dietary intake. The findings suggest that postprandial testing may better capture subtle metabolic benefits of weight loss.
