Dairy and industrial sources of trans fat do not impair peripheral insulin sensitivity in overweight women

Background: The2majordietarysourcesoftransfattyacids(TFAs) are partially hydrogenated oils and ruminant-derived products. Epidemiologic data suggest that chronic consumption of industrial sources of TFAs could be damaging to insulin sensitivity, but intervention studies on this issue have remained inconclusive. Objective: The trial was designed to compare the effects of dairy compared with industrial sources of TFAs on insulin sensitivity in overweight women. Design: Sixty-three healthy women with abdominal obesity [waist circumference .88 cm and a body mass index (in kg/m 2 ) .28] were recruited. After a run-in period, the volunteers were randomly assigned to consume 1 of 3 four-week diets: 60 g low-TFA lipids/d (0.54 g/d; n = 21), ruminant TFA–rich lipids (4.86 g/d; n = 21), or industrial TFA–rich lipids (5.58 g/d; n = 21). Changes in peripheral insulin sensitivity were assessed by using hyperinsulinemiceuglycemic clamps. Results: After the intervention period, fasting glycemia and insulinemia and insulin sensitivity were not significantly modified in either group (P . 0.05). Conclusions: These data indicate that consumption of dairy- and industrial-source TFAs for 4 wk at nutritional levels do not impair peripheral insulin sensitivity in insulin-resistant women. Our study may not preassess the effects of TFAs in normal insulinsensitive individuals. This trial was registered at clinicaltrials.gov as NCT00617435. Am J Clin Nutr 2009;90:1–7.