While this study does not directly implicate fat as the cause of insulin resistance, it does lean in that direction.
Prolonged reliance on fat-rich diet led to inability to lose weight even in the presence of exercise (and thus caloric deficit). Only the carbohydrate-rich diet combined with exercise led to fat loss and improved insulin sensitivity.
Prolonged adaptation to fat-rich diet and training; effects on body fat stores and insulin resistance in man. - PubMed - NCBI
"...Across the 7 weeks body weight was reduced (1.3+/-0.3%) in all three groups, however body fat mass was decreased only in the CHO-Train (13%) and maintained in the two FAT-groups. RER at rest was similarly decreased (5%) in the three groups. Plasma insulin tended to decrease (16%) in CHO-Train (P=0.065) and remained unchanged in the two FAT-groups. In contrast plasma glucose (4.6+/-0.1 mmol/l) and plasma FA (453+/-27 micromol/l) remained unchanged across the 7 weeks. The calculated insulin resistance index HOMA-R(mod) was significantly decreased by 19% in CHO-train but remained unchanged in both of the FAT-groups, whereas the calculated insulin secretion index HOMA-beta(mod) was unchanged in all three groups.
CONCLUSION: In the present study we demonstrate that despite of a mild energy deficit body fat mass was maintained after prolonged adaptation to fat-rich diet both when normal physical activity was maintained and when training was performed. In contrast a significant decrease in fat mass was observed when carbohydrate-rich diet and training was combined. Furthermore we observed that the insulin resistance index was significantly decreased only when training was combined with a carbohydrate-rich diet."
Prolonged reliance on fat-rich diet led to inability to lose weight even in the presence of exercise (and thus caloric deficit). Only the carbohydrate-rich diet combined with exercise led to fat loss and improved insulin sensitivity.
Prolonged adaptation to fat-rich diet and training; effects on body fat stores and insulin resistance in man. - PubMed - NCBI
"...Across the 7 weeks body weight was reduced (1.3+/-0.3%) in all three groups, however body fat mass was decreased only in the CHO-Train (13%) and maintained in the two FAT-groups. RER at rest was similarly decreased (5%) in the three groups. Plasma insulin tended to decrease (16%) in CHO-Train (P=0.065) and remained unchanged in the two FAT-groups. In contrast plasma glucose (4.6+/-0.1 mmol/l) and plasma FA (453+/-27 micromol/l) remained unchanged across the 7 weeks. The calculated insulin resistance index HOMA-R(mod) was significantly decreased by 19% in CHO-train but remained unchanged in both of the FAT-groups, whereas the calculated insulin secretion index HOMA-beta(mod) was unchanged in all three groups.
CONCLUSION: In the present study we demonstrate that despite of a mild energy deficit body fat mass was maintained after prolonged adaptation to fat-rich diet both when normal physical activity was maintained and when training was performed. In contrast a significant decrease in fat mass was observed when carbohydrate-rich diet and training was combined. Furthermore we observed that the insulin resistance index was significantly decreased only when training was combined with a carbohydrate-rich diet."
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