Despite the importance of randomized, dose-response studies for proper evaluation of effective clinical interventions, there have been no dose-response studies on the effects of exercise amount on abdominal obesity, a major risk factor for metabolic syndrome, diabetes, and cardiovascular disease. One hundred seventy-five sedentary, overweight men and women with mild to moderate dyslipidemia were randomly assigned to participate for 6 mo in a control group or for approximately 8 mo in one of three exercise groups: 1) low amount, moderate intensity, equivalent to walking 12 miles/wk (19.2 km) at 40-55% of peak oxygen consumption; 2) low amount, vigorous intensity, equivalent to jogging 12 miles/wk at 65-80% of peak oxygen consumption; or 3) high amount, vigorous intensity, equivalent to jogging 20 miles/wk (32.0 km). Computed tomography scans were analyzed for abdominal fat. Controls gained visceral fat (8.6 +/- 17.2%; P = 0.001). The equivalent of 11 miles of exercise per week, at either intensity, prevented significant accumulation of visceral fat. The highest amount of exercise resulted in decreased visceral (-6.9 +/- 20.8%; P = 0.038) and subcutaneous (-7.0 +/- 10.8%; P < 0.001) abdominal fat. Significant gains in visceral fat over only 6 mo emphasize the high cost of continued inactivity. A modest exercise program, consistent with recommendations from the Centers for Disease Control/American College of Sports Medicine (CDC/ACSM), prevented significant increases in visceral fat. Importantly, a modest increase over the CDC/ACSM exercise recommendations resulted in significant decreases in visceral, subcutaneous, and total abdominal fat without changes in caloric intake.
"Although the results show only a slight decrease in VAT with RT as the sole intervention, the clinical significance can be gauged by studying large prospective intervention studies examining the correlations between changes in VAT with exercise training and variables of metabolic risk. In STRRIDE, data suggests that the reduction of as little as 11 cm2 in VAT is significantly related to changes in low-density lipoprotein (LDL) particle number, LDL size, and insulin sensitivity.110 Data from STRRIDE also revealed that a higher amount of AET resulted in greater reductions in measures of central obesity but there was no dose–response relationship between intensity of exercise and changes in VAT.58 Similarly, a 2007 review by Ohkawara et al. found that there is a dose–response relationship between amount of exercise and changes in VAT in obese subjects without metabolic-related disorders.111 "
[Show abstract][Hide abstract] ABSTRACT: Biological aging is typically associated with a progressive increase in body fat mass and a loss of lean body mass. Owing to the metabolic consequences of reduced muscle mass, it is understood that normal aging and/or decreased physical activity may lead to a higher prevalence of metabolic disorders. Lifestyle modification, specifically changes in diet, physical activity, and exercise, is considered the cornerstone of obesity management. However, for most overweight people it is difficult to lose weight permanently through diet or exercise. Thus, prevention of weight gain is thought to be more effective than weight loss in reducing obesity rates. A key question is whether physical activity can extenuate age-related weight gain and promote metabolic health in adults. Current guidelines suggest that adults should accumulate about 60 minutes of moderate-intensity physical activity daily to prevent unhealthy weight gain. Because evidence suggests that resistance training may promote a negative energy balance and may change body fat distribution, it is possible that an increase in muscle mass after resistance training may be a key mediator leading to better metabolic control.
Annals of the New York Academy of Sciences 11/2012; 1281(1). DOI:10.1111/j.1749-6632.2012.06785.x · 4.38 Impact Factor
"Since overall energy expenditure was matched between the training groups, and no evidence of different dietary intake within or between any of the groups was found, we expected that body composition would change equally (27,28). We found that IWT led to a greater reduction in body weight, fat mass, and abdominal visceral adiposity than CWT. "
[Show abstract][Hide abstract] ABSTRACT: OBJECTIVEdTo evaluate the feasibility of free-living walking training in type 2 diabetes patients, and to investigate the effects of interval-walking training versus continuous-walking training upon physical fitness, body composition, and glycemic control. RESEARCH DESIGN AND METHOD
SdSubjects with type 2 diabetes were randomized to a control (n = 8), continuous-walking (n = 12), or interval-walking group (n = 12). Training groups were prescribed five sessions per week (60 min/session) and were controlled with an accelerometer and a heart-rate monitor. Continuous walkers performed all training at moderate intensity, whereas interval walkers alternated 3-min repetitions at low and high intensity. Before and after the 4-month intervention, the following variables were measured: VO 2 max, body composition, and glycemic control (fasting glucose, HbA 1c , oral glucose tolerance test, and continuous glucose monitoring [CGM]). RESULTSdTraining adherence was high (89 6 4%), and training energy expenditure and mean intensity were comparable. VO 2 max increased 16.1 6 3.7% in the interval-walking group (P , 0.05), whereas no changes were observed in the continuous-walking or control group. Body mass and adiposity (fat mass and visceral fat) decreased in the interval-walking group only (P , 0.05). Glycemic control (elevated mean CGM glucose levels and increased fasting insulin) wors-ened in the control group (P , 0.05), whereas mean (P = 0.05) and maximum (P , 0.05) CGM glucose levels decreased in the interval-walking group. The continuous walkers showed no changes in glycemic control. CONCLUSION
SdFree-living walking training is feasible in type 2 diabetes patients. Con-tinuous walking offsets the deterioration in glycemia seen in the control group, and interval walking is superior to energy expenditure–matched continuous walking for improving physical fitness, body composition, and glycemic control.
Diabetes Care 01/2012; 36(2). DOI:10.2337/dc12-0658 · 8.42 Impact Factor
"More recently, the World Health Organization's (WHO's) "Global Recommendations on Physical Activity for Health"  following the 2008 "Physical Activity Guidelines for Americans"  has proposed more than 150 min of moderate-intensity PA per week to maintain body weight. The evidence for this recommendation was obtained from short-term clinical trials indicating that PA in the range of 13-26 metabolic equivalent (MET)-hours per week resulted in 1-3% weight loss, consistent with weight stability over the long term [4-6]. Thirteen MET-hours are roughly equivalent to brisk walking for 150 min. "
[Show abstract][Hide abstract] ABSTRACT: Although physical activity recommendations for public health have focused on locomotive activity such as walking and running, it is uncertain how much these activities contribute to overall physical activity level (PAL). The purpose of the present study was to determine the contribution of locomotive activity to PAL using total step counts measured in a calorimeter study.
PAL, calculated as total energy expenditure divided by basal metabolic rate, was evaluated in 11 adult men using three different conditions for 24-hour human calorimeter measurements: a low-activity day (L-day) targeted at a low active level of PAL (1.45), and a high-frequency moderate activity day (M-day) or a high-frequency vigorous activity day (V-day) targeted at an active level of PAL (1.75). These subjects were permitted only light activities except prescribed activities. In a separate group of 41 adults, free-living PAL was evaluated using doubly-labeled water (DLW). In both experiments, step counts per day were also measured using an accelerometer.
In the human calorimeter study, PAL and step counts were 1.42 ± 0.10 and 8,973 ± 543 steps/d (L-day), 1.82 ± 0.14 and 29,588 ± 1,126 steps/d (M-day), and 1.74 ± 0.15 and 23,755 ± 1,038 steps/d (V-day), respectively. In the DLW study, PAL and step counts were 1.73 ± 0.15 and 10,022 ± 2,605 steps/d, and there was no significant relationship between PAL and daily step counts.
These results indicate that an enormous number of steps are needed for an active level of PAL if individuals extend physical activity-induced energy expenditure by only locomotive activity. Therefore, non-locomotive activity such as household activity should also play a significant role in increasing PAL under free-living conditions.
BMC Research Notes 11/2011; 4(1):512. DOI:10.1186/1756-0500-4-512
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