Exercise-induced improvements in glucose effectiveness are blunted by a high glycemic diet in adults with prediabetes

Abstract

Background: Glucose effectiveness (GE) refers to the ability of glucose to influence its own metabolism through insulin-independent mechanisms. Exercise training improves GE, however; little is known about how dietary interventions such as manipulating the glycemic index of diets, interact with exercise-induced improvements in GE in at-risk populations. Objective: To determine the effect of glycemic index of the diet on exercise-induced enhancement of GE in people with obesity and insulin resistance. Design: A randomized, controlled, parallel-group, repeated-measures study. Participants: 33 adults with obesity and pre-diabetes (17 males, 65.7±4.3 yrs, 34.9±4.2 kg/m 2) Interventions: Participants were recruited into a 12-week exercise training program (1 hr/d, 5 d/wk at ~85% of maximum heart rate) while being randomized to concurrently receive either a low (EX-LOG: 40±0.3 au) or high (EX-HIG: 80±0.6 au) glycemic diet. A 75-g oral-glucosetolerance test (OGTT) was performed before and after the intervention and GE was calculated using the Nagasaka equation. Results: Both EX-LOG and EX-HIG groups had similar improvements in weight (8.6±5.1 Kg, P<0.001), VO 2max (6±3.5 ml. kg −1 .min −1 , P<0.001) and clamp-measured peripheral insulin resistance (1.7±0.9 mg.kg −1 .min −1 , P<0.001

Nutritional Strategies in Prediabetes: A Scoping Review of Recent Evidence

“…Three studies utilized nonspecific low GI diets as the intervention diet. Hari et al [ 74 ] and Solomon et al [ 98 ] employed a low GI diet (40 arbitrary units) as intervention and a high GI diet (80 arbitrary units) as control, concurrent with a 12-week aerobic exercise training program. These diets were formulated using the 2002 GI tables from Foster-Powell et al [ 112 ] and contained different foods isocaloric to the participants’ individual requirements.…”

“…Of the three studies with the nonspecific low GI diet as intervention, two established that insulin sensitivity and peripheral insulin resistance were improved and decreased respectively, whereas nonsignificant differences in insulin sensitivity between low and high GI diet were found in the study by Hari et al [ 74 , 98 , 101 ]. Pancreatic β-cell function was successfully preserved by having a low GI diet, ensuring effective glucose metabolism [ 101 ].…”

“…This was further supported by Solomon et al who found that postprandial glucose levels improved in a low GI diet while pancreatic β-cell function was impaired in a high GI diet [ 98 ]. All three studies demonstrated significant weight loss in low GI diets [ 74 , 98 , 101 ].…”

“…Eight studies (57.1%) recorded statistically significant improvements [ 22 , 26 , 27 , 33 , 34 , 36 , 53 , 93 ]. An assessment of performance in physical activity or aerobic fitness, often measured by maximal peak oxygen consumption (VO 2 max), across 10 studies showed improvement in seven of them (70%) [ 27 , 29 , 40 , 71 , 74 , 98 , 111 ].…”

“…Thirty of 52 studies (57.7%) that investigated changes in weight and/or BMI, reported significant improvement postintervention [ 17 , 22 , 24 , 26 , 27 , 29 , 31 , 32 , 33 , 40 , 43 , 58 , 59 , 61 , 65 , 71 , 74 , 77 , 84 , 87 , 88 , 90 , 93 , 98 , 99 , 101 , 102 , 109 , 110 , 111 ]. Similar proportions of statistically significant findings were observed for the waist and hip circumferences and/or waist-to-hip ratio (17/32 studies, 53.1%) [ 17 , 18 , 24 , 26 , 32 , 33 , 38 , 58 , 61 , 62 , 84 , 87 , 88 , 101 , 102 , 108 , 109 ] as well as systolic and diastolic blood pressure (16/31 studies, 51.6%) [ 17 , ...…”