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

Abstract

BackgroundRed 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). MethodsForty-nine subjects without diabetes [15 men and 34 women, age, 35.6±15.7 years, body mass index (BMI), 27±5.9kg/m2] underwent two 4-week weight-stable dietary interventions in a randomized crossover design. The insulin sensitivity index (ISI) was calculated from the last 30min of a continuous low-dose insulin (25mU/kg·h) and glucose (4mg/kg·min) infusion test (LDIGIT 120–150min) at the end of each diet. ResultsThe population fell into two very discrete groups: those with a very low insulin response in the LDIGIT 120–150min on HMD (Group 1<56pmol/L, n=24), and those with relatively normal insulin responses (Group 2>56pmol/L, n=25). Group 2 had significantly higher insulin concentrations [(median and interquartile range) 153, 180 for HMD vs. 123, 149pmol/L for HWD; P=0.019] and glucose concentrations [(mean±standard deviation) 7.4±1.3 for HMD vs.6.7±1.2mmol/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). ConclusionsA 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.