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Red, processed meat, grains decrease insulin sensitivity in adults with obesity, prediabetes
Adults with overweight or obesity and impaired glucose tolerance assigned to a diet high in red and processed meat and grains for 4 weeks saw reduced insulin sensitivity vs. those assigned to a diet high in whole grains, nuts, dairy and legumes, study findings show.
In a randomized crossover trial, researchers also observed that participants of normal weight with normal glucose tolerance did not experience the same effect.
“It would appear that a dramatic improvement in diet quality could increase insulin sensitivity by nearly 50% in only 4 weeks in people at risk for developing [type 2 diabetes],” Yoona Kim, of the School of Pharmacy and Medical Sciences at the University of South Australia, and colleagues wrote. “No effect was seen in people with a lower risk for developing [type 2 diabetes] as assessed by low [low-dose insulin and glucose infusion test] insulin levels.”
Kim and colleagues analyzed data from 49 adults without diabetes (34 women; mean age, 36 years; mean BMI, 27 kg/m²) assigned to two 4-week, weight-stable dietary interventions. Interventions included a diet high in red and processed meat and refined grains (recommended daily consumption, 200-300 g of red meat; 50 g processed meat; 4-6 servings of refined grains based on participants’ weight; 1-2 servings each of fruits and vegetables and minimal dairy), and a diet high in whole grains, nuts, dairy and legumes with no red meat (recommended daily consumption, 4 servings of low-fat dairy; 3-4 servings of whole grain breads, rice and pasta; 70-150 g chicken or seafood; 150-225 g cooked legumes). Total energy was matched in the two diets; there was a minimum 2-week washout period between interventions. Researchers measured participants’ insulin sensitivity index (ISI), calculated from the last 30 minutes of a continuous low-dose insulin and glucose infusion test at the end of each diet.
Researchers observed that insulin values after the infusion tests were not normally distributed, with participants falling into either very low insulin concentrations of about 20 pmol/L to 40 pmol/L or normal to very high insulin concentrations. Researchers divided the cohort into two groups, with a median insulin of 33 pmol/L in group 1 and median insulin of 122 pmol/L in group 2.
In group 1, researchers observed no between-diet differences in insulin and glucose concentrations or log ISI, before or after adjustment for activity level. However, insulin concentrations were higher for those in group 2 when assigned to the red meat diet vs. the diet without red meat (median and interquartile ranges, 153 pmol/L and 180 pmol/L vs. 123 pmol/L and 149 pmol/L, respectively). Glucose concentrations at 120 to 150 minutes were also higher for those in group 2 assigned to the red meat diet vs. the intervention without red meat (7.4 mmol/L vs. 6.7 mmol/L). ISI was also lower after the red meat diet vs. the intervention without red meat (median and interquartile range, 21.1 and 34.2 vs. 31.6 and 39.4, respectively). Adjusting for activity level did not attenuate the diet effect, according to researchers.
In group 2, log ISI was correlated with BMI (r = –0.51; P = .009), fat mass (r = –0.55; P = .004), and self-reported activity levels (r = –0.45; P = .024).
“A healthy diet without weight loss or exercise may reduce your risk of type 2 diabetes,” Peter Clifton, MD, PhD, of University of South Australia, told Endocrine Today. “We believe the quality of the carbohydrate is the most important component, and we need to test this with all other components of the diet held constant. For those who struggle with their weight, changing the quality of their diet may help.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.