This study was undertaken to investigate the impact of overfeeding on peripheral insulin resistance in lean and overweight individuals and the role of inflammation in the adipose tissue and systemically. The study sample included 36 healthy individuals who underwent 28 days of overfeeding by adding 1,250 kcal/day (45% fat) to their dietary intake. Results showed that overfeeding resulted in moderate weight gain, with significant increases in total and abdominal fat mass and liver fat deposition. At the same time, an increase in fasting insulin as well as an 11% decrease in peripheral insulin sensitivity was measured by hyperinsulinemic clamp. However, no changes in subcutaneous adipose tissue macrophage infiltration or inflammatory gene expression were observed. There was a significant increase in circulating C-reactive protein and monocyte chemoattractant protein-1. These findings suggest that the insulin resistance induced by weight gain in short-term overfeeding appear to precede the immune activation and macrophage recruitment into subcutaneous adipose tissue in humans.
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