Kazunori Ohkawara

A dose-response relation between aerobic exercise and visceral fat reduction: systematic review of clinical trials

Objective:It has been suggested that exercise has preferential effects on visceral fat reduction. However, the dose–response effect remains unclear because of limited evidence from individual studies. The purpose of this study was to systematically review the current literature to establish whether reduction of visceral fat by aerobic exercise has a dose–response relationship.Methods:A database search was performed (PubMed, 1966–2006) with appropriate keywords to identify studies exploring the effects of aerobic exercise as a weight loss intervention on visceral fat reduction. Visceral fat reduction was expressed as the percentage of visceral fat change per week (%ΔVF/w). The energy expenditure by aerobic exercise was expressed as ∑(metabolic equivalents × h per week (METs·h/w)).Results:Nine randomized control trials and seven non-randomized control trials were selected. In most of the studies, the subjects performed aerobic exercise generating 10 METs·h/w or more. Among all the selected groups (582 subjects), visceral fat decreased significantly (P<0.05) in 17 groups during the intervention, but not in the other 4 groups. There was no significant relationship between METs·h/w from aerobic exercise and %ΔVF/w in all the selected groups. However, when subjects with metabolic-related disorders were not included (425 subjects), METs·h/w from aerobic exercise had a significant relationship with %ΔVF/w (r=−0.75). Moreover, visceral fat reduction was significantly related to weight reduction during aerobic exercise intervention, although a significant visceral fat reduction may occur without significant weight loss.Conclusion:These results suggest that at least 10 METs·h/w in aerobic exercise, such as brisk walking, light jogging or stationary ergometer usage, is required for visceral fat reduction, and that there is a dose–response relationship between aerobic exercise and visceral fat reduction in obese subjects without metabolic-related disorders.

METs in Adults While Playing Active Video Games: A Metabolic Chamber Study

PURPOSE Active video game systems controlled through arm gestures and motions (Nintendo Wii Sports) and video games controlled through force plate (Wii Fit Plus) are becoming increasingly popular. This study was performed to determine the energy expenditure (EE) during Wii Fit Plus and Wii Sports game activities. METHODS Twelve adult men and women performed all the activities of Wii Sports (five activities: golf, bowling, tennis, baseball, and boxing) and Wii Fit Plus (63 activities classified as yoga, resistance, balance, and aerobic exercises). Each activity was continued for at least 8 min to obtain a steady-state EE. Because EE was assessed in an open-circuit indirect metabolic chamber consisting of an airtight room (20,000 or 15,000 L), subjects were freed of apparatus to collect expired gas while playing the games. MET value was calculated from resting EE and steady-state EE during activity. RESULTS The mean MET values of all 68 activities were distributed over a wide range from 1.3 METs (Lotus Focus) to 5.6 METs (single-arm stand). The mean MET values in yoga, balance, resistance, and aerobic exercise of Wii Fit Plus and Wii Sports were 2.1, 2.0, 3.2, 3.4, and 3.0 METs, respectively. Forty-six activities (67%) were classified as light intensity (<3 METs), and 22 activities (33%) were classified as moderate intensity (3.0-6.0 METs). There were no vigorous-intensity activities (>6.0 METs). CONCLUSIONS Time spent playing one-third of the activities supplied by motion- and gesture-controlled video games can count toward the daily amount of exercise required according to the guidelines provided by the American College of Sports Medicine and the American Heart Association, which focus on 30 min of moderate-intensity daily physical activity 5 d x wk(-1).

Classifying household and locomotive activities using a triaxial accelerometer.

The purpose of this study was to develop a new algorithm for classifying physical activity into either locomotive or household activities using a triaxial accelerometer. Sixty-six volunteers (31 men and 35 women) participated in this study and were separated randomly into validation and cross-validation groups. All subjects performed 12 physical activities (personal computer work, laundry, dishwashing, moving a small load, vacuuming, slow walking, normal walking, brisk walking, normal walking while carrying a bag, jogging, ascending stairs and descending stairs) while wearing a triaxial accelerometer in a controlled laboratory setting. Each of the three signals from the triaxial accelerometer was passed through a second-order Butterworth high-pass filter to remove the gravitational acceleration component from the signal. The cut-off frequency was set at 0.7 Hz based on frequency analysis of the movements conducted. The ratios of unfiltered to filtered total acceleration (TAU/TAF) and filtered vertical to horizontal acceleration (VAF/HAF) were calculated to determine the cut-off value for classification of household and locomotive activities. When the TAU/TAF discrimination cut-off value derived from the validation group was applied to the cross-validation group, the average percentage of correct discrimination was 98.7%. When the VAF/HAF value similarly derived was applied to the cross-validation group, there was relatively high accuracy but the lowest percentage of correct discrimination was 63.6% (moving a small load). These findings suggest that our new algorithm using the TAU/TAF cut-off value can accurately classify household and locomotive activities.

Real-time estimation of daily physical activity intensity by a triaxial accelerometer and a gravity-removal classification algorithm.

We have recently developed a simple algorithm for the classification of household and locomotive activities using the ratio of unfiltered to filtered synthetic acceleration (gravity-removal physical activity classification algorithm, GRPACA) measured by a triaxial accelerometer. The purpose of the present study was to develop a new model for the immediate estimation of daily physical activity intensities using a triaxial accelerometer. A total of sixty-six subjects were randomly assigned into validation (n 44) and cross-validation (n 22) groups. All subjects performed fourteen activities while wearing a triaxial accelerometer in a controlled laboratory setting. During each activity, energy expenditure was measured by indirect calorimetry, and physical activity intensities were expressed as metabolic equivalents (MET). The validation group displayed strong relationships between measured MET and filtered synthetic accelerations for household (r 0·907, P < 0·001) and locomotive (r 0·961, P < 0·001) activities. In the cross-validation group, two GRPACA-based linear regression models provided highly accurate MET estimation for household and locomotive activities. Results were similar when equations were developed by non-linear regression or sex-specific linear or non-linear regressions. Sedentary activities were also accurately estimated by the specific linear regression classified from other activity counts. Therefore, the use of a triaxial accelerometer in combination with a GRPACA permits more accurate and immediate estimation of daily physical activity intensities, compared with previously reported cut-off classification models. This method may be useful for field investigations as well as for self-monitoring by general users.

Effects of Aerobic Exercise on Metabolic Syndrome Improvement in Response to Weight Reduction

Objective: The objective was to test effects of aerobic exercise training on metabolic syndrome (MetSyn) improvement in response to weight reduction.

Effects of aerobic exercise and obesity phenotype on abdominal fat reduction in response to weight loss

OBJECTIVE:To test the effects on abdominal fat reduction of adding aerobic exercise training to a diet program and obesity phenotype in response to weight loss.DESIGN:A prospective clinical trial with a 14-week weight-loss intervention design.SETTING AND PARTICIPANTS:In total, 209 overweight and obese women were assigned to four subgroups depending on type of treatment and the subjects obesity phenotype: diet alone (DA) with intra-abdominal fat (IF) obesity (≥mean IF area), diet plus exercise (DE) with IF obesity, DA with abdominal subcutaneous fat (ASF) obesity (<mean IF area) and DE with ASF obesity. Abdominal fat areas were evaluated by CT scans, with values adjusted for selected variables.RESULTS:Values were adjusted for age, menopausal status and change in body weight and total fat mass. The IF reductions were significantly (P<0.0001) greater in subjects with IF obesity phenotype (−45.1 cm2) compared to the ASF obesity phenotype (−22.2 cm2). The ASF reductions were significantly (P<0.001) greater for subjects with ASF obesity (−74.5 cm2) compared to IF obesity (−55.5 cm2). For IF obesity, the IF reduction was significantly (P<0.01) greater in the DE group (−49.3 cm2) than in the DA group (−37.8 cm2).CONCLUSION:These results suggest that for individuals with IF obesity, the efficacy on reducing IF of adding aerobic exercise training to a diet-alone weight-reduction program is more prominent (−49.3 cm2/−37.8 cm2=1.3 times) compared with DA. Moreover, abdominal fat reduction was found to be modified by obesity phenotype in response to weight loss.

A new approach for flow-through respirometry measurements in humans

Indirect whole room calorimetry is commonly used in studies of human metabolism. These calorimeters can be configured as either push or pull systems. A major obstacle to accurately calculating gas exchange rates in a pull system is that the excurrent flow rate is increased above the incurrent flow rate, because the organism produces water vapor, which also dilutes the concentrations of respiratory gases in the excurrent sample. A common approach to this problem is to dry the excurrent gases prior to measurement, but if drying is incomplete, large errors in the calculated oxygen consumption will result. The other major potential source of error is fluctuations in the concentration of O(2) and CO(2) in the incurrent airstream. We describe a novel approach to measuring gas exchange using a pull-type whole room indirect calorimeter. Relative humidity and temperature of the incurrent and excurrent airstreams are measured continuously using high-precision, relative humidity and temperature sensors, permitting accurate measurement of water vapor pressure. The excurrent flow rates are then adjusted to eliminate the flow contribution from water vapor, and respiratory gas concentrations are adjusted to eliminate the effect of water vapor dilution. In addition, a novel switching approach is used that permits constant, uninterrupted measurement of the excurrent airstream while allowing frequent measurements of the incurrent airstream. To demonstrate the accuracy of this approach, we present the results of validation trials compared with our existing system and metabolic carts, as well as the results of standard propane combustion tests.

Weight Loss Reduces Plasma Endothelin-1 Concentration in Obese Men

Obesity is associated with endothelial dysfunction that may contribute to the development of diabetes, hypertension, and atherosclerosis. Endothelin-1 (ET-1), which is produced mostly by vascular endothelial cells, has potent vasoconstrictor and proliferative activity in vascular smooth muscle cells and, therefore, has been implicated in regulation of vascular tonus and the progression of atherosclerosis, suggesting that ET-1 may be important in endothelial dysfunction. We studied whether diet-induced weight loss (i.e., lifestyle modification) affects plasma ET-1 concentration in obese individuals. We measured plasma ET-1 concentration in seven obese men (age: 48 ± 4 years old, body mass index: 27.7 ± 0.5 kg/m2) before and after a 3-month, diet-induced weight reduction program (i.e., lifestyle modification program). Caloric restriction reduced body weight from 78 ± 3 to 68 ± 2 kg (P < 0.001) and resulted in 12.1 ± 1.2% reduction in body mass index (24.3 ± 0.3 kg/m2, P < 0.0001). After the weight reduction program, systolic and diastolic blood pressure significantly decreased (128 ± 7 vs. 115 ± 4 mm Hg, P < 0.05 and 88 ± 4 vs. 77 ± 2 mm Hg, P < 0.01, respectively). The plasma level of ET-1 significantly decreased after the program (5.1 ± 0.4 vs. 4.0 ± 0.3 pg/ml, P < 0.05). The percentage systolic blood pressure reduction and percentage plasma ET-1 concentration reduction was in a linear relationship (r = 0.86, P < 0.05). Furthermore, the relationship between percentage weight reduction and percentage plasma ET-1 concentration reduction was linear (r = 0.87, P < 0.05). We conclude that weight loss by low-calorie diet (i.e., lifestyle modification) reduces plasma ET-1 concentration in obese individuals. This reduction may contribute to the improvement of obesity-induced endothelial dysfunction.

Effects of increased meal frequency on fat oxidation and perceived hunger.

Consuming smaller, more frequent meals is often advocated as a means of controlling body weight, but studies demonstrating a mechanistic effect of this practice on factors associated with body weight regulation are lacking. The purpose of this study was to compare the effect of consuming three (3M) vs. six meals (6M) per day on 24‐h fat oxidation and subjective ratings of hunger.

Effects of additional resistance training during diet-induced weight loss on bone mineral density in overweight premenopausal women

Bone loss accompanies a diet-induced weight loss and could be prevented with a combination of exercises. This study was conducted to examine the effects of additional resistance training during diet-induced weight loss on whole-body and selected regional bone mineral density (BMD). The participants of a 14-week weight-loss study were 42 overweight premenopausal Japanese women who were randomly placed in either a diet-only group (D; n = 21) or a diet plus resistance training group (DR; n = 21). Whole-body BMD and body composition, lumbar spine BMD, and 1/3 radial BMD were measured by dual-energy X-ray absorptiometry before and after the intervention. Bone formation and resorption markers were also measured. Thirty-five participants (83%) completed the study. Individuals in groups D (n = 17) and DR (n = 18) lost 6.2 ± 3.5 kg and 8.6 ± 3.6 kg body weight, respectively. Reductions in percentage fat mass and fat mass in group DR were significantly greater than in group D; lean mass decreased significantly in both groups. The effect of time on whole-body BMD was significant (−0.3%); however, whole-body bone mineral content, lumbar spine BMD, and 1/3 radial BMD remained unchanged. There were no significant timeby-group interactions in the whole-body and regional BMD and bone markers. These results suggest that additional resistance training during weight loss has no effect on BMD in overweight premenopausal Japanese women. Further long-term studies with large numbers of subjects are needed.