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1.  Lifestyle-Induced Decrease in Fat Mass Improves Adiponectin Secretion in Obese Adults 
Several studies have identified relationships between weight loss and adipokine levels; however none have looked at the combined effect of aerobic exercise training with consumption of a low, or high glycemic diet. We examined the effects of 12-weeks of aerobic exercise combined with either a low- (GI: ~40, LoGIX) or high-glycemic (GI: ~80, HiGIX) diet on plasma leptin and adiponectin (total and high molecular weight - HMW) in 27 older obese adults (age 65±0.5 years; BMI 34.5±0.7 kg/m2).
Insulin sensitivity was calculated from an oral glucose tolerance test (ISIOGTT). Fasting HMW adiponectin and leptin were quantified from plasma samples obtained prior to the ISIOGTT. Glucose and insulin measures were obtained before and every 30 min during the test. Dual-energy X-ray absorptiometry and computerized tomography was used to determine body composition and to quantify subcutaneous and visceral abdominal adiposity, respectively.
Fasting leptin was significantly decreased in both groups (LoGIX, pre: 33.8±4.7, post: 19.2±4.5; HiGIX, pre: 27.9±4.2, post: 11.9±2.2 ng/ml, P=0.004), and HMW adiponectin was significantly increased (LoGIX, pre: 1606.9±34.6, post: 3502.3±57; HiGIX, pre: 3704.8±38.1, post: 4284.3±52.8 pg/ml; P=0.003) following the 12-week intervention. Total body fat was reduced after both interventions, and visceral fat mass was inversely correlated with HMW adiponectin, while subcutaneous fat correlated with leptin.
The data suggest that exercise training, independent of dietary GI, favorably alters HMW adiponectin and leptin secretion, and that a reduction in visceral fat mass is a key factor regulating HMW adiponectin in older obese persons.
PMCID: PMC3991752  PMID: 24614337
adiponectin; leptin; aerobic exercise; glycemic diet
2.  Exercise training with weight loss and either a high or low glycemic diet reduces metabolic syndrome severity in older adults 
Annals of nutrition & metabolism  2012;61(2):135-141.
The efficacy of combining carbohydrate quality with exercise on metabolic syndrome risk is unclear. Thus, we determined the effects of exercise training with a low or high glycemic diet on metabolic syndrome severity (Z-score).
Twenty-one adults (66.2 ± 1.1 yr; BMI = 35.3 ± 0.9 kg/m2) with metabolic syndrome were randomized to 12 weeks of exercise (60 minutes/d for 5 d/week at ~85% HRmax) and provided a low-glycemic (n=11; LoGIx) or high glycemic (n=10; HiGIx) diet. Z-scores were determined from: blood pressure, triglycerides (TG), high-density lipoproteins (HDL), fasting plasma glucose (FPG), and waist circumference (WC) before and after the intervention. Body composition, aerobic fitness, insulin resistance, and non-esterfied fatty acid (NEFA) suppression were also assessed.
LoGIx and HiGIx decreased body mass and insulin resistance and increased aerobic fitness comparably (p < 0.05). LoGIx and HiGIx decreased the Z-score similarly, as each intervention decreased blood pressure, TG, FPG, and WC (p < 0.05). HiGIx tended to suppress NEFA during insulin stimulation compared to LoGIx (p = 0.06).
Our findings highlight that exercise with weight loss reduces metabolic syndrome severity whether individuals were randomized to a high or low glycemic index diet.
PMCID: PMC3586384  PMID: 23036993
aging; obesity; lifestyle modification; diabetes; impaired glucose tolerance
3.  Exercise Training and Dietary Glycemic Load May Have Synergistic Effects on Insulin Resistance in Older Obese Adults 
Annals of Nutrition & Metabolism  2009;55(4):326-333.
The aim of this study was to assess the combined effects of exercise and dietary glycemic load on insulin resistance in older obese adults.
Eleven men and women (62 ± 2 years; 97.6 ± 4.8 kg; body mass index 33.2 ± 2.0) participated in a 12-week supervised exercise program, 5 days/week, for about 1 h/day, at 80–85% of maximum heart rate. Dietary glycemic load was calculated from dietary intake records. Insulin resistance was determined using the euglycemic (5.0 mM) hyperinsulinemic (40 mU/m2/min) clamp.
The intervention improved insulin sensitivity (2.37 ± 0.37 to 3.28 ± 0.52 mg/kg/min, p < 0.004), increased VO2max (p < 0.009), and decreased body weight (p < 0.009). Despite similar caloric intakes (1,816 ± 128 vs. 1,610 ± 100 kcal/day), dietary glycemic load trended towards a decrease during the study (140 ± 10 g before, vs. 115 ± 8 g during, p < 0.04). The change in insulin sensitivity correlated with the change in glycemic load (r = 0.84, p < 0.009). Four subjects reduced their glycemic load by 61 ± 8%, and had significantly greater increases in insulin sensitivity (78 ± 11 vs. 23 ± 8%, p < 0.003), and decreases in body weight (p < 0.004) and plasma triglycerides (p < 0.04) compared to the rest of the group.
The data suggest that combining a low-glycemic diet with exercise may provide an alternative and more effective treatment for insulin resistance in older obese adults.
PMCID: PMC2853590  PMID: 19844089
Diabetes; Obesity; Aging; Insulin sensitivity; Physical activity; Glycemic index

Results 1-3 (3)