Consumption of red and processed meat and refined grains for 4 weeks decreases insulin sensitivity in insulin-resistant adults: A randomized crossover study

Background. Red and processed meat and refined grains are associated with an increased risk of type 2 diabetes. Interventions are limited. We hypothesized that a diet high in red and processed meat and refined grains (HMD) would decrease insulin sensitivity compared to a diet high in whole grains, nuts, dairy and legumes with no red meat (HWD). Methods. Forty-nine subjects without diabetes [15 men and 34 women, age, 35.6 +/- 15.7 years, body mass index (BMI), 27 +/- 5.9 kg/m(2)] underwent two 4-week weight-stable dietary interventions in a randomized crossover design. The insulin sensitivity index (ISI) was calculated from the last 30 min of a continuous low-dose insulin (25 mU/kg center dot h) and glucose (4 mg/kg center dot min) infusion test (LDIGIT (120_isomin)) at the end of each diet. Results. The population fell into two very discrete groups: those with a very low insulin response in the LDIGIT (120-4.5omin) on HMD (Group 1 < 56 pmol/L, n = 24), and those with relatively normal insulin responses (Group 2 > 56 pmol/L, n = 25). Group 2 had significantly higher insulin concentrations [(median and interquartile range) 153, 180 for HMD vs. 123, 149 pmol/L for HWD; P = 0.019] and glucose concentrations [(mean standard deviation) 7.4 +/- 1.3 for HMD vs.6.7 +/- 1.2 mmol/L for HWD; P = 0.05], resulting in a significantly decreased ISI [(median and interquartile range) 21.1, 34.2 for HMD vs. 31.6, 39.4 for HWD; P = 0.014] compared to HWD. Log ISI after HMD was significantly correlated with BMI (r = -0.5; P = 0.009), fat mass (r = -0.55; P = 0.004) and self-reported activity levels (r = -0.45; P = 0.024). Conclusions. A dietary pattern high in red and processed meat and refined grains decreased insulin sensitivity compared to a dietary pattern high in whole grains, nuts, dairy products and legumes only in relatively insulin-resistant adults. (C) 2016 Elsevier Inc. All rights reserved.