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1.  Exercise and diet enhance fat oxidation and reduce insulin resistance in older obese adults 
Journal of applied physiology (Bethesda, Md. : 1985)  2008;104(5):10.1152/japplphysiol.00890.2007.
Older, obese, and sedentary individuals are at high risk of developing diabetes and cardiovascular disease. Exercise training improves metabolic anomalies associated with such diseases, but the effects of caloric restriction in addition to exercise in such a high risk group are not known. Changes in body composition and metabolism during a lifestyle intervention were investigated in twenty three older, obese men and women (aged 66 ± 1 years, BMI 33.2 ± 1.4 kg.m−2) with impaired glucose tolerance. All volunteers undertook twelve weeks of aerobic exercise training (5 days per week for 60 min @ 75% VO2max) with either normal caloric intake (eucaloric group, 1901 ± 277−1, n = 12) or a reduced-calorie diet (hypocaloric group, 1307 ± 70−1, n = 11), as dictated by nutritional counseling. Body composition (decreased fat mass; maintained fat-free mass), aerobic fitness (VO2max), leptinemia, insulin sensitivity, and intramyocellular lipid accumulation (IMCL) in skeletal muscle improved in both groups (P < 0.05). Improvements in body composition, leptin and basal fat oxidation were greater in the hypocaloric group. Following the intervention there was a correlation between the increase in basal fat oxidation and the decrease in IMCL (r = −0.53, P = 0.04). In addition, basal fat oxidation was associated with circulating leptin after (r = 0.65, P = 0.0007), but not before the intervention (r = 0.05, P = 0.84). In conclusion, these data show that exercise training improves resting substrate oxidation and creates a metabolic milieu that appears to promote lipid utilization in skeletal muscle, thus facilitating a reversal of insulin resistance. We also demonstrate that leptin sensitivity is improved, but that such a trend may rely on reducing caloric intake in addition to exercise training.
PMCID: PMC3860368  PMID: 18323464
obesity; leptin; substrate oxidation; insulin sensitivity
2.  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
3.  Effects of Exercise and Caloric Restriction on Insulin Resistance and Cardiometabolic Risk Factors in Older Obese Adults—A Randomized Clinical Trial 
The prevalence of insulin resistance, metabolic syndrome, and cardiovascular disease is greatest in older obese patients, and effective evidence-based treatment strategies are lacking.
A prospective controlled study was conducted on 24 older (65.5 ± 5.0 years) obese (body mass index, 34.3 ± 5.2 kg/m2) adults with clinically diagnosed metabolic syndrome. We examined the effect of exercise alone (EX) or exercise combined with moderate caloric restriction (−500 kcal, EX + CR) on metabolic and cardiovascular risk factors. Measures of insulin sensitivity assessed by euglycemic hyperinsulinemic clamp and by oral glucose tolerance test, lipid profiles, blood pressure, body composition, abdominal fat, and aerobic capacity were all obtained before and after the interventions.
Both groups experienced significant weight loss, but the reduction was greater in the EX + CR group than in the EX group (−6.8 ± 2.7 kg vs −3.7 ± 3.4 kg, respectively, p = .02). Both interventions improved insulin sensitivity (2.4 ± 2.4 mg/kg FFM/min and 1.4 ± 1.7 mg/kgFFM/min, respectively, p < .001) and indices of metabolic syndrome (systolic/diastolic blood pressure, waist circumference, glucose, and triglycerides; p < .05). High-density lipoprotein levels remained unchanged. Total abdominal, subcutaneous, and visceral fat; aerobic capacity; and total and low-density lipoprotein cholesterol were also improved. With the exception of weight loss and subcutaneous fat, there was no difference in the magnitude of improvement between the interventions.
These data suggest that exercise alone is an effective nonpharmacological treatment strategy for insulin resistance, metabolic syndrome, and cardiovascular disease risk factors in older obese adults.
PMCID: PMC2691195  PMID: 19164269
Aging; Obesity; Diabetes; Impaired glucose tolerance
4.  Effects of Aging on Basal Fat Oxidation in Obese Humans 
Basal fat oxidation decreases with age. In obesity it is not known whether this age-related process occurs independently of changes in body composition and insulin sensitivity. Therefore, body composition, resting energy expenditure (REE), basal substrate oxidation, and maximal oxygen consumption (VO2max) were measured in ten older (age 60 ± 4 years; mean ± S.E.M.) and ten younger (age 35 ± 4 years) body mass index-matched, obese, normal glucose tolerant individuals. Fasting blood samples were also collected. Older subjects had slightly elevated fat mass (32.2 ± 7.1 vs. 36.5 ± 6.7 kg; P = 0.16), however waist circumference (WC) was not different between groups (104.3 ± 10.3 vs. 102.1 ± 12.6 cm; P = 0.65). Basal fat oxidation was 22% lower (1.42 ± 0.14 vs. 1.17 ± 0.22 mg/kg fat-free mass (FFM)/min; P = 0.03) in older subjects. VO2max was also decreased in older individuals (44.6 ± 7.1 vs. 38.3 ± 6.0 ml/kgFFM/min; P = 0.03), but neither insulin sensitivity, lipemia, nor leptinemia were different between groups (P > 0.05). Fat oxidation was most related to age (r = −0.61, P = 0.003) and VO2max (r = 0.52, P = 0.01). These data suggest that aging per se is responsible for reduced basal fat oxidation and maximal oxidative capacity in older obese individuals, independent of changes in insulin resistance, body mass, and abdominal fat. This indicates that age, in addition to obesity, is an independent risk factor for weight gain and for the metabolic complications of elevated body fat.
PMCID: PMC2528955  PMID: 18640394
aging; substrate oxidation; energy expenditure

Results 1-4 (4)