A low-glycemic index diet combined with exercise reduces insulin resistance, postprandial hyperinsulinemia, and glucose-dependent insulinotropic polypeptide responses in obese, prediabetic humans

Thomas Pj Solomon, Jacob M Haus, Karen R Kelly, Marc D Cook, Julianne Filion, Michael Rocco, Sangeeta R Kashyap, Richard M Watanabe, Hope Barkoukis, John P Kirwan

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91 Citations (Scopus)

Abstract

BACKGROUND: The optimal lifestyle intervention that reverses diabetes risk factors is not known.

OBJECTIVE: We examined the effect of a low-glycemic index (GI) diet and exercise intervention on glucose metabolism and insulin secretion in obese, prediabetic individuals.

DESIGN: Twenty-two participants [mean ± SEM age: 66 ± 1 y; body mass index (in kg/m(2)): 34.4 ± 0.8] underwent a 12-wk exercise-training intervention (1 h/d for 5 d/wk at ≈ 85% of maximum heart rate) while randomly assigned to receive either a low-GI diet (LoGIX; 40 ± 0.3 units) or a high-GI diet (HiGIX; 80 ± 0.6 units). Body composition (measured by using dual-energy X-ray absorptiometry and computed tomography), insulin sensitivity (measured with a hyperinsulinemic euglycemic clamp with [6,6-(2)H(2)]-glucose), and oral glucose-induced insulin and incretin hormone secretion were examined.

RESULTS: Both groups lost equal amounts of body weight (-8.8 ± 0.9%) and adiposity and showed similar improvements in peripheral tissue (+76.2 ± 14.9%) and hepatic insulin sensitivity (+27.1 ± 7.1%) (all P < 0.05). However, oral glucose-induced insulin secretion was reduced only in the LoGIX group (6.59 ± 0.86 nmol in the prestudy compared with 4.70 ± 0.67 nmol in the poststudy, P < 0.05), which was a change related to the suppressed postprandial response of glucose-dependent insulinotropic polypeptide. When corrected for changes in β cell glucose exposure, changes in insulin secretion were attenuated in the LoGIX group but became significantly elevated in the HiGIX group.

CONCLUSIONS: Although lifestyle-induced weight loss improves insulin resistance in prediabetic individuals, postprandial hyperinsulinemia is reduced only when a low-GI diet is consumed. In contrast, a high-GI diet impairs pancreatic β cell and intestinal K cell function despite significant weight loss. These findings highlight the important role of the gut in mediating the effects of a low-GI diet on type 2 diabetes risk reduction.

Original languageEnglish
Pages (from-to)1359-68
Number of pages10
JournalThe American journal of clinical nutrition
Volume92
Issue number6
DOIs
Publication statusPublished - Dec 2010

Keywords

  • Adiposity
  • Aged
  • Combined Modality Therapy
  • Exercise
  • Female
  • Gastric Inhibitory Polypeptide
  • Glucose Tolerance Test
  • Glycemic Index
  • Humans
  • Hyperinsulinism
  • Insulin
  • Insulin Resistance
  • Liver
  • Male
  • Obesity
  • Postprandial Period
  • Weight Loss

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