Metabolic inflexibility in individuals with obesity assessed by near-infrared spectroscopy

Objective: To non-invasively evaluate differences in oxidative metabolism in individuals with obesity compared to normal weight using the near-infrared spectroscopy and vascular occlusion technique during hyperglycaemia. Methods: In all, 16 normal-weight individuals (body mass index: 21.3 ± 1.7 kg/m²) and 13 individuals with obesity (body mass index: 34.4 ± 2.0 kg/m²) had five vascular occlusion tests (pre, 30, 60, 90 and 120 min after glucose ingestion). Oxygen utilization was estimated from the area under the curve of the deoxyhemoglobin [HHb] signal during occlusion. Muscle reperfusion was derived from the area above the curve after cuff release. Results: The deoxyhemoglobin area under the curve during occlusion of the normal-weight individuals increased from 15,732 ± 2344 (%. s) at pre to 18,930 ± 3226 (%. s) (p < 0.05) at 90 min after glucose ingestion. The deoxyhemoglobin area under the curve during occlusion decreased significantly from 14,695 ± 3341 (%. s) at pre to 11,273 ± 1825 (%. s) (p < 0.05) and 11,360 ± 1750 (%. s) (p < 0.05) at 30 and 60 min, respectively, after glucose ingestion. The area above the curve of deoxyhemoglobin during reperfusion decreased significantly from 6450 ± 765 (%. s) at pre to 4830 ± 963 (%. s) (p < 0.05) at 60 min and to 4210 ± 595 (%. s) (p < 0.01) at 90 min in normal-weight individuals after glucose ingestion, with no changes observed in individuals with obesity. Conclusion: This study confirmed in vivo and non-invasively the metabolic inflexibility of skeletal muscle in individuals with obesity during hyperglycaemia.