Significant changes in VLDL-triacylglycerol and glucose tolerance in obese subjects following ten days of training

Extremely short duration high intensity interval training substantially improves insulin action in young healthy males

BACKGROUND

Traditional high volume aerobic exercise training reduces cardiovascular and metabolic disease risk but involves a substantial time commitment. Extremely low volume high-intensity interval training (HIT) has recently been demonstrated to produce improvements to aerobic function, but it is unknown whether HIT has the capacity to improve insulin action and hence glycemic control.

METHODS

Sixteen young men (age: 21 +/- 2 y; BMI: 23.7 +/- 3.1 kg x m-2; VO2peak: 48 +/- 9 ml x kg-1 x min-1) performed 2 weeks of supervised HIT comprising of a total of 15 min of exercise (6 sessions; 4-6 x 30-s cycle sprints per session). Aerobic performance (250-kJ self-paced cycling time trial), and glucose, insulin and NEFA responses to a 75-g oral glucose load (oral glucose tolerance test; OGTT) were determined before and after training.

RESULTS

Following 2 weeks of HIT, the area under the plasma glucose, insulin and NEFA concentration-time curves were all reduced (12%, 37%, 26% respectively, all P < 0.001). Fasting plasma insulin and glucose concentrations remained unchanged, but there was a tendency for reduced fasting plasma NEFA concentrations post-training (pre: 350 +/- 36 v post: 290 +/- 39 micromol x l-1, P = 0.058). Insulin sensitivity, as measured by the Cederholm index, was improved by 23% (P < 0.01), while aerobic cycling performance improved by approximately 6% (P < 0.01).

CONCLUSION

The efficacy of a high intensity exercise protocol, involving only ~250 kcal of work each week, to substantially improve insulin action in young sedentary subjects is remarkable. This novel time-efficient training paradigm can be used as a strategy to reduce metabolic risk factors in young and middle aged sedentary populations who otherwise would not adhere to time consuming traditional aerobic exercise regimes.

Efficacy of a pedometer-based physical activity program on parameters of diabetes control in type 2 diabetes mellitus

The aim of the study was to determine whether a recommendation to walk 10000 steps per day would result in significant improvements in glycemic control, insulin sensitivity, and cardiovascular risk in patients with type 2 diabetes mellitus. The study was a 6-week randomized controlled trial that included 30 patients with type 2 diabetes mellitus. After 10 days of baseline activity, patients were randomized into 2 groups: control and active. The control group (n = 15) was instructed to continue with their baseline activity for 6 weeks. The active group (n = 15) was instructed to walk at least 10000 steps per day 5 or more days per week, for 6 weeks. Data relevant to glycemic control and other parameters of health were collected at study weeks 0 and 6. There were no differences in the baseline activity between groups (P = .36). Subjects in the active group significantly increased physical activity by 69% during the intervention phase of the study (P = .002), whereas there was no change in the physical activity of the control group (P > .05). High-density lipoprotein cholesterol and resting energy expenditure significantly increased in the active group (P < .05). Finally, plasminogen activator inhibitor 1 (PAI-1) activity was reduced by exercise relative to the control group (P = .03). There were no differences in any other study parameters during the 6-week study. In conclusion, short-term intervention with a pedometer increased physical activity and positively affected plasminogen activator inhibitor 1 activity in previously inactive patients with type 2 diabetes mellitus. The use of a pedometer may prove to be an effective tool for promoting healthy lifestyle changes that include daily physical activity and self-monitoring of therapeutic goals.

Effects of resistance or aerobic exercises on metabolic parameters in obese women who are not on a diet

This longitudinal, controlled clinical study was conducted to compare the effects of resistance exercise (RE) and aerobic exercise (AE) on body mass index (BMI), weight, fat mass (FM), serum lipid profile, and insulin resistance in obese women who cannot adhere to energy-restricted diets. A total of 60 obese women with severe eating disorders were evaluated. Patients were randomly divided into 3 groups: control group with no exercise (n=20), group 1 with AE (n=20), and group 2 with RE (n=20). Demographic and anthropometric measurements were taken. Serum lipid fractions and fasting (FGlc) and postprandial glucose insulin (PGlc) levels were measured. Insulin resistance was calculated with use of homeostasis model assessment (HOMA-IR). Total body FM was measured by bioelectric impedance analysis. After 12 wk of exercise, significant decreases in BMI, waist and weight measurements, and FGlc, PGlc, triglyceride, and total cholesterol levels were noted in each of the study groups. Reduced low-density lipoprotein cholesterol level and FM and HOMA-IR measurements were observed only in group 1 (with AE). This study indicated that AE and RE training induces improvement in body fat composition and has a favorable metabolic effect in obese women with severe eating disorders.

Effect of Exercise Timing on Postprandial Lipemia in Hypertriglyceridemic Men

We investigated the effect of exercise timing on attenuation of postprandial hyper-triglyceridemia (PHTG) in individuals with hypertriglyceridemia (HTG). Subjects were 10 males (TG = 290.1 ± 28.5 mg/dl). Each subject performed a control trial (Ctr), 12-hr premeal exercise trial (12-hr Pre), and 24-hr premeal exercise trial (24-hr Pre). In each trial, subjects had a fat-rich meal. In the exercise trials they jogged on a treadmill at 60% of their [Formula: see text] for 1 hr at a designated time. Blood samples were taken at 0 (immediately before the fat meal), and at 2, 4, 6, 8, and 24 hrs after the meal. The results indicated that plasma TG concentrations in 12-hr Pre were lower than in Ctr and 24-hr Pre (p <  0.03). The area score under the TG concentration curve (TG AUC score) in 12-hr Pre was 37% and 33% lower than in 24-hr Pre and Ctr (p <  0.02), respectively. Insulin concentrations in 12-hr Pre were lower than Ctr and 24-hr Pre (p <  0.001). The plasma nonesterified fatty acid (NEFA) concentration was higher in 12-hr Pre than in both 24-hr Pre and Ctr (p <  0.003). There were no trial differences in both HDLtot-Ch and HDL2-Ch. These results suggest that exercising 12 hrs prior to a fat-meal intake significantly reduces PHTG response whereas exercising 24 hrs prior to the meal does not attenuate PHTG in hypertriglyceridemic men. The effect of an acute exercise bout on PHTG lowering may be short-lived and diminished by 24 hrs. Key words: high-density lipoprotein cholesterol, triglyceride, lipoprotein lipase, insulin

Improvements in glucose tolerance in obese males with abnormal glucose tolerance following 10 days of aerobic exercise

BACKGROUND

Aerobic exercise training has been shown to produce beneficial changes in glucose tolerance and insulin sensitivity in obese individuals if performed at high enough intensities and/or durations. We examined the effects of a moderate intensity, short-term exercise training protocol on glucose tolerance in obese males with glucose intolerance.

METHODS

Fourteen abdominally obese, sedentary males with normal glucose tolerance (NGT; n = 7) and abnormal glucose tolerance (AGT; n = 7) completed 40 min of exercise bouts for 10 consecutive days at approximately 75% of age-predicted maximum heart rate. Fasting glucose and insulin levels, and glucose tolerance and insulin response to glucose were measured before and after the training period.

RESULTS

Participants did not experience significant mass loss during the 10-day investigation. Individuals in the AGT group experienced significant (P < 0.05) improvement in glucose tolerance [glucose area: 1,763.67 (255.98) mmol L(-1) x 120 min(-1) vs. 1,682.98 (266.91) mmol L(-1) x 120 min(-1)] and fasting insulin levels [44.57 (7.58) microU mL(-1) vs. 36.14 (3.97) microU mL(-1)] as a result of training. Significant (P < 0.05) reductions in fasting glucose concentrations [5.82 (0.19) mmol L(-1) vs. 5.42 (0.18) mmol L(-1)] and a decrease in fasting insulin concentrations [44.71 (9.39) microU mL(-1) vs. 35.0 (7.15) microU mL(-1); P = 0.064] were observed in the NGT group following the training period.

CONCLUSIONS

The data suggest that moderate, short-term exercise without concomitant mass loss is effective in improving glucose tolerance and insulin response to a glucose load in obese males with abnormal glucose tolerance.

Effects of short-term exercise training on plasminogen activator inhibitor (PAI-1)

PURPOSE

To observe the effects of exercise training on plasminogen activator inhibitor, type-1 (PAI-1), tissue plasminogen activator (tPA), and associated metabolic variables in sedentary men and women.

METHODS

A randomized, controlled experimental design was used to examine the influence of 10 d of moderate-intensity exercise training on measures of fibrinolysis. Sixteen men and 16 women between the ages of 50 and 70 yr were randomly assigned to exercise (EX) and control groups (CON) that were balanced for gender and hormone replacement therapy. Blood samples were collected on days 1, 2, 11, and 12 for measurement of plasma PAI-1, tPA, insulin, glucose, and triglyceride. Subjects in EX performed 50 min of treadmill walking at an intensity corresponding to 65% of heart rate reserve each day for 10 consecutive days.

RESULTS

There were no significant changes in PAI-1, tPA, or associated metabolic variables between EX and CON during the intervention period. Within EX subjects, those with higher body fatness had a significant decrease in insulin and triglyceride compared with those with lower body fatness. However, no changes in fibrinolytic measures were observed within these subgroups.

CONCLUSIONS

Short-term exercise training does not change PAI-1 levels in normal, asymptomatic men and women. In addition, modest decreases in insulin and triglyceride in individuals with elevated body fatness do not result in changes in PAI-1 after short-term training. It appears likely that decreases in PAI-1 with exercise training require decreases in adiposity and/or marked changes in metabolic variables.

Significant enhancements in glucose tolerance and insulin action in centrally obese subjects following ten days of training

OBJECTIVE

The objective of the study was to determine the effects of short-term exercise on glucose tolerance and insulin response to a glucose load in centrally obese individuals.

DESIGN

75 g oral glucose tolerance tests (OGTT) were performed prior to participation and 24 hours after the last exercise session. Exercise bouts were 40 minutes in duration and consisted of treadmill walking and cycle ergometry at 70-80% of age-predicted maximum heart rate (APHR(max)).

PARTICIPANTS

Eleven sedentary, centrally obese men [mean (SE): Mass, 119.1 (5.4) kg; BMI, 37.7 (1.8) kg/m(-2); waist-to-hip ratio (WHR), 0.97 (0.01); age 31.7 (2.4) years] were studied before and after 10 days of aerobic exercise training.

RESULTS

No significant change (p >.05) in body mass was noted following 10 days of exercise as compared with preparticipation [119.1 (5.4) kg versus 118.9 (5.4) kg]. Fasting plasma glucose concentration was significantly lower (p < 0.05) following 10 days of exercise as compared with preexercise [5.58 (0.15) mmol/L versus 5.27 (0.12) mmol/L]. No significant change (p > 0.05) in fasting plasma insulin concentration, however, was observed following 10 days of exercise training as compared with preexercise [276.2 (33.7) pmol/L versus 225.3 (35.9) pmol/L]. Plasma insulin concentrations at 60 minutes and 120 minutes were significantly decreased (p < 0.05) when comparing the preexercise to the postexercise OGTT [60: 1264.2 (88.3) pmol/L versus 1103.5 (81.1) pmol/L; 120: 1066.9 (110.5) pmol/L versus 764.1 (106.2) pmol/L]. Plasma glucose concentration at 120 minutes. was also significantly reduced (p < 0.05) after 10 days of exercise as compared with preexercise [6.09 (0.24) mmol/L versus 5.39 (0.22) mmol/L]. Area under the glucose curve was significantly (p < 0.05) reduced after 10 days of exercise as compared with preparticipation [944.6 (44.4) mmol/L/120 min versus 884.4 (43.2) mmol/L/120 min]. Area under the insulin curve was also significantly decreased (p < 0.05) following 10 days of exercise training as compared with preexercise [126,890 (9014.0) pmol/L/120 min versus 109,445 (7,888.9) pmol/L/120 min].

CONCLUSIONS

These data suggest that short-term exercise may improve glucose tolerance and insulin response to a glucose load in centrally obese men.

Effects of physical activity on insulin action and glucose tolerance in obesity

PURPOSE

The purpose of this paper is to examine the effect of physical activity on glucose tolerance in relation to obesity.

METHODS

We reviewed current literature, with particular emphasis on randomized clinical trials, to prepare an evidence-based evaluation of the effects of physical activity on glucose intolerance in obesity.

RESULTS

This literature review indicates that physical activity has favorable effects on reducing insulin resistance in obesity and among patients with type 2 diabetes mellitus. Improvement in glucose tolerance is less consistently observed and is related to intensity of exercise, collateral changes in adiposity, the interval between exercise and testing of glucose tolerance, and the baseline severity of glucose intolerance.

CONCLUSION

A review of currently published clinical trial data supports the conclusion that physical activity can reduce insulin resistance and improve glucose intolerance in obesity.