Energy expenditure of deskwork when sitting, standing or alternating positions.

BACKGROUND: Recent guidelines recommend accruing 2-4h of standing or light activity during the working day. Use of sit-stand desks could achieve this goal, but whether standing can meaningfully increase energy expenditure (EE) is unclear. AIMS: To study EE, heart rate, feelings and productivity during deskwork while sitting, standing or alternating positions. METHODS: We measured EE by indirect calorimetry in working adults over three randomly ordered 60-min conditions while performing deskwork: continuous sitting (SIT), 30min of each standing and sitting (STAND-SIT) and continuous standing (STAND). We also assessed heart rate, productivity and self-reported energy, fatigue and pain. Linear mixed models compared minute-by-minute EE and heart rate across conditions. Non-parametric tests compared remaining outcomes across conditions. RESULTS: The study group comprised 18 working adults. Compared with SIT, STAND-SIT engendered an additional 5.5±12.4 kcal/h (7.8% increase) and STAND engendered an additional 8.2±15.9 kcal/h (11.5% increase) (both P < 0.001). Alternating positions to achieve the recommended 4h/day of standing could result in an additional 56.9 kcal/day for an 88.9kg man and 48.3 kcal/day for a 75.5kg woman. STAND-SIT and STAND also increased heart rate over SIT by 7.5±6.8 and 13.7±8.8 bpm, respectively (both P < 0.001). We observed no meaningful differences in feelings or productivity. CONCLUSIONS: Desk-based workers could increase EE without added discomfort by using a sit-stand desk. These findings inform future research on sit-stand desks as a part of workplace interventions to increase EE and potentially improve health.

Brief report: symmetricity of radiographic and MRI-detected structural joint damage in persons with knee pain--the Joints on Glucosamine (JOG) Study.

OBJECTIVE: Most MRI-based osteoarthritis (OA) studies have focused on a single knee per person and thus, data on bilaterality is sparse. Study aim was to describe symmetricity of MRI-detected OA features in a cohort of subjects with knee pain. DESIGN: Participants were 169 subjects with chronic knee pain who had 3 T MRI of both knees using the same protocol as in the Osteoarthritis Initiative. Knees were read for cartilage damage, bone marrow lesions (BMLs), and meniscal damage according to the Whole-Organ Magnetic Resonance Imaging Score (WORMS) system. Chi(2) tests were used to compare the proportion of knees with unilateral tissue pathology to the proportion what would be expected if both knees were independent. We further used percent agreement and linear weighted kappa statistics to describe agreement of cartilage damage and BMLs in the same articular plates. RESULTS: 51.2% of participants were men, mean age was 52.1 (±6.2), mean BMI was 29.0 kg/m(2) (±4.1). All plates showed a significant higher degree of symmetricity for cartilage damage as evidenced by weighted kappas ranging from 0.32 to 0.59. For BMLs the degree of symmetricity was higher for the patella, trochlea, medial tibia, lateral femur, and medial femur; for meniscal damage the degree of unilaterality was lower for all medial meniscal subregions but not all lateral. Kappas ranged between 0.52 and 0.68 for cartilage and 0.30 and 0.55 for BMLs for the four subregions with highest agreement. CONCLUSION: A higher degree of symmetricity of tissue damage than expected by chance was observed in this cohort of subjects with knee pain.

African American women exhibit similar adherence to intervention but lose less weight due to lower energy requirements.

BACKGROUND: African American (AA) women have been shown to lose less weight than Caucasian women in response to behavioral interventions. Our objective was to examine adherence to intervention and metabolic factors that may explain this difference. DESIGN AND SUBJECTS: We examined longitudinal changes in body weight and energy expenditure (EE), and objective assessment of physical activity (PA) and energy intake (EI) during 6 months of a weight-loss intervention program, including prescribed calorie restriction and increased PA in 66 Caucasian and 39 AA severely obese women. Comparisons were also made in 25 Caucasian and 25 AA women matched for initial body weight. RESULTS: The AA women lost 3.6 kg less weight than Caucasian women. Total daily EE (TDEE) and resting metabolic rate (RMR) adjusted for fat free mass (FFM) were significantly lower in the AA women, whereas the decrease in RMR in response to weight loss was greater in Caucasian women. Adherence to the prescribed PA and change in PA in response to intervention were similar in AA and Caucasian women. Prescribed EI (1794±153 and 1806±153 kcal per day) and measured EI during intervention (2591±371 vs 2630±442 kcal per day) were nearly identical in matched AA and Caucasian women. However, the AA women lost significantly less body weight due to lower energy requirements (2924±279 vs 3116±340 kcal per day; P<0.04), resulting in a lower energy deficit (333±210 vs 485±264 kcal per day). CONCLUSION: Adherence to the behavioral intervention was similar in AA and Caucasian women. However, neglecting to account for the lower energy requirements in AA women when calculating the energy prescription resulted in a lower level of calorie restriction and, hence, less body weight loss. Therefore, to achieve similar weight loss in AA women, the prescribed caloric restriction cannot be based on weight alone, but must be lower than in Caucasians, to account for lower energy requirements.

Susceptibility artifacts detected on 3T MRI of the knee: frequency, change over time and associations with radiographic findings: data from the joints on glucosamine study.

OBJECTIVE: To determine the prevalence of intraarticular susceptibility artifacts and to detect longitudinal changes in the artifacts, on 3T magnetic resonance imaging (MRI) of the knee in a cohort of patients with knee pain, and to assess the association of susceptibility artifacts with radiographic intraarticular calcifications. DESIGN: Three hundred and forty-six knees of 177 subjects aged 35-65 were included. 3T MRI was performed at baseline and at 6 months. Baseline radiographs were assessed for presence/absence of linear/punctate calcifications within the tibiofemoral joint (TFJ) space. Corresponding MRIs were assessed for susceptibility artifacts (i.e., linear/punctate hypointensities) in the TFJ space on coronal dual-echo steady-state (DESS) sequences. Kappa statistics were applied to determine agreement between findings on baseline DESS and radiography. Changes in artifacts over time were recorded. RESULTS: In the medial compartment, 13 (4%) of the knees showed susceptibility artifacts at baseline. Six knees had persistent artifacts and six knees had incident artifacts at follow-up. Agreement between DESS and radiography was κ = 0.18 (-0.15, 0.51) in the medial compartment. Frequency of artifacts in the lateral compartment was low (2%). CONCLUSION: Susceptibility artifacts detected on knee MRI are not frequent, and likely correspond to vacuum phenomena as they commonly change over time and are not associated with intraarticular calcifications. Radiologists should be aware of these artifacts as they can interfere with cartilage segmentation.

High energy expenditure masks low physical activity in obesity.

OBJECTIVE: To investigate energy expenditure in lean and obese individuals, focusing particularly on physical activity and severely obese individuals. DESIGN: Total daily energy expenditure (TDEE) was assessed using doubly labeled water, resting metabolic rate (RMR) by indirect calorimetry, activity energy expenditure (AEE) by difference and time spent in physical activity by multisensor activity monitors. SUBJECTS: In all, 177 lean, Class I and severely obese individuals (age 31-56 years, body mass index 20-64 kg m(-2)) were analyzed. RESULTS: All components of energy expenditure were elevated in obese individuals. For example, TDEE was 2404±95 kcal per day in lean and 3244±48 kcal per day in Class III obese individuals. After appropriate adjustment, RMR was similar in all groups. Analysis of AEE by body weight and obesity class indicated a lower AEE in obese individuals. Confirming lower physical activity, obese individuals spent less time engaged in moderate-to-vigorous physical activity (2.7±1.3, 1.8±0.6, 2.0±1.4 and 1.2±1.0 h per day in lean, Class I, Class II and Class III individuals) and more time in sedentary behaviors. CONCLUSIONS: There was no indication of metabolic efficiency in even the severely obese, as adjusted RMR was similar across all groups. The higher AEE observed in the obese is consistent with a higher cost of activities due to higher body weight. However, the magnitude of the higher AEE (20-25% higher in obese individuals) is lower than expected (weight approximately 100% higher in Class III individuals). Confirming a lower volume of physical activity in the obese, the total time spent in moderate-to-vigorous physical activity and average daily metabolic equivalent of task level were lower with increasing obesity. These findings demonstrate that high body weight in obese individuals leads to a high TDEE and AEE, which masks the fact that they are less physically active, which can be influenced by duration or intensity of activity, than in lean individuals.

Effect of a lifestyle intervention on change in cardiorespiratory fitness in adults with type 2 diabetes: results from the Look AHEAD Study.

OBJECTIVE: To examine the effect of an intensive lifestyle weight loss intervention (ILI) compared to diabetes support and education (DSE) on changes in fitness and physical activity in the Look AHEAD trial. DESIGN: Randomized clinical trial to compare a lifestyle intervention for weight loss with a DSE condition in individuals with type 2 diabetes. SUBJECTS: Data from 4376 overweight or obese adults with type 2 diabetes (age=58.7+/-6.8 years, body mass index (BMI)=35.8+/-5.8 kg/m(2)) who completed 1 year of the Look AHEAD trial and had available fitness data were analyzed. INTERVENTION: Subjects were randomly assigned to DSE or ILI. DSE received standard care plus three education sessions over the 1-year period. ILI included individual and group contact throughout the year, restriction in energy intake and 175 min per week of prescribed physical activity. MEASUREMENTS: Fitness was assessed using a submaximal graded exercise test. Physical activity was assessed by questionnaire in a subset of 2221 subjects. RESULTS: Change in fitness was statistically greater in ILI vs DSE after adjustment for baseline fitness (20.9 vs 5.7%; P<0.0001). Multivariate analysis showed that change in fitness was greater in overweight vs obese Class II and III (P<0.05). Physical activity increased by 892+/-1694 kcal per week in ILI vs 108+/-1254 kcal per week in DSE (P<0.01). Changes in fitness (r=0.41) and physical activity (r=0.42) were significantly correlated with weight loss (P<0.0001). CONCLUSIONS: The ILI was effective in increasing physical activity and improving cardiorespiratory fitness in overweight and obese individuals with type 2 diabetes. This effect may add to weight loss in improving metabolic control in patients in lifestyle intervention programs.

Weight loss treatment influences untreated spouses and the home environment: evidence of a ripple effect.

OBJECTIVES: To examine whether a weight loss program delivered to one spouse has beneficial effects on the untreated spouse and the home environment. METHODS: We assessed untreated spouses of participants in three sites of Look AHEAD, a multicenter randomized controlled trial evaluating the impact of intentional weight loss on cardiovascular outcomes in overweight individuals with type 2 diabetes. Participants and spouses (n=357 pairs) were weighed and completed measures of diet and physical activity at 0 and 12 months. Spouses completed household food and exercise environment inventories. We examined differences between spouses of participants assigned to the intensive lifestyle intervention (ILI) or to the enhanced usual care (DSE; diabetes support and education). RESULTS: Spouses of ILI participants lost -2.2+/-4.5 kg vs -0.2+/-3.3 kg in spouses of DSE participants (P<0.001). In addition, more ILI spouses lost > or =5% of their body weight than DSE spouses (26 vs 9%, P<0.001). Spouses of ILI participants also had greater reductions in reported energy intake (P=0.007) and percent of energy from fat (P=0.012) than DSE spouses. Spouse weight loss was associated with participant weight loss (P<0.001) and decreases in high-fat foods in the home (P=0.05). CONCLUSION: The reach of behavioral weight loss treatment can extend to a spouse, suggesting that social networks can be utilized to promote the spread of weight loss, thus creating a ripple effect.

Effects of supervised and unsupervised physical activity programmes for weight loss.

OBJECTIVES: Physical activity is important for weight management. However, it remains unclear what type of physical activity prescription/programme is optimal for increasing physical activity during a standard behavioural weight loss intervention. This study examined changes in physical activity after a 12-week supervised programme prescribed in minutes per week (SUP-PA), an unsupervised programme prescribed in minutes per week (UNSUP-PA) and an unsupervised programme prescribed in steps per day (STEP). METHODS: Fifty-two adults who were overweight or obese (age: 43.5 ± 10.1 years, BMI: 31.5 ± 3.5 kg·m-2) were randomized to STEP (n = 18), UNSUP-PA (n = 17) and SUP-PA (n = 17). Subjects attended weekly in-person group intervention sessions and were prescribed a calorie-restricted diet (1,200-1,800 kcals·day-1) combined with increased physical activity (150 min·week-1 or 10,000 steps·day-1 with 2,500 brisk steps·day-1). RESULTS: All three groups significantly increased moderate-to-vigorous physical activity (STEP: 80.6 ± 218.5 min·week-1, UNSUP-PA: 112.9 ± 180.4 min·week-1 and SUP-PA: 151.1 ± 174.0 min·week-1, p < 0.001) with no differences between groups (p = 0.94) or group by time interaction (p = 0.81). In addition, there were no significant differences in weight loss between the groups (p = 0.81). CONCLUSIONS: In this short-term study, all three physical activity programmes increased physical activity and elicited modest weight loss when combined with a standard behavioural weight loss intervention.

Response to a standard behavioral weight loss intervention by age of onset of obesity.

BACKGROUND: The purpose of this study was to examine weight loss, physical activity, fitness and diet changes in response to a standard behavioral weight loss intervention in adults with self-reported juvenile onset (n = 61) or adult onset (n = 116) obesity. METHODS: Participants (n = 177; 43.0 ± 8.6 years; body mass index [BMI] = 33.0 ± 3.4 kg m-2) engaged in an 18-month standard behavioral weight loss intervention. Participants were randomized into three different intervention groups as part of the larger parent trial. BMI, physical activity, fitness and diet were assessed at baseline, 6, 12 and 18 months. Separate adjusted mixed models were constructed using SAS version 9.4 (SAS Institute, Cary, NC). RESULTS: There was significant weight loss, increased physical activity, improved fitness and reduced caloric intake over time (p < 0.001). There were no significant differences in these outcome variables by obesity onset group. However, there was a significant group by time interaction for fitness (p = 0.001), with the adult onset making significantly greater gains in fitness from baseline to 6 months (p < 0.001); however, this difference was no longer present at 12 or 18 months. CONCLUSIONS: With the exception of fitness at 6 months, weight loss, physical activity and diet did not differ between juvenile onset and adult onset participants, suggesting that those with juvenile onset obesity are equally responsive to a standard behavioral weight loss intervention in adulthood.

Applying a technology-based system for weight loss in adults with obesity.

OBJECTIVE: The aim of this study was to compare an in-person, group-based behavioral weight loss intervention to technology-based interventions in adults with obesity. METHODS: Adults (N = 39; body mass index: 39.5 ± 2.8 kg m-2; age: 39.9 ± 11.5 years) participated in a 6-month program with randomization to one of three intervention groups: standard behavioral weight loss, a technology-based system combined with a monthly intervention telephone call (TECH) or an enhanced technology-based system combined with a monthly intervention telephone call (EN-TECH). All groups were prescribed an energy-restricted diet and physical activity. Assessments occurred at 0, 3 and 6 months. Separate mixed-effects models using unstructured dependence structure were fit to the outcomes. RESULTS: Weight loss (least square means ± standard error) at 6 months was -6.57 ± 1.65 kg in standard behavioral weight loss, -5.18 ± 1.72 kg in TECH and -6.25 ± 1.95 kg in EN-TECH (p-value for time effect ≤ 0.0001). A similar pattern was observed for change in body mass index, waist circumference and percent body fat. There was a decrease in total energy intake (p = 0.0005) and percent dietary fat intake (p = 0.0172), and physical activity increased (p = 0.0003). CONCLUSIONS: Findings provide initial information on the use of technology-based interventions that include wearable devices combined with brief monthly telephone calls for weight loss in adults with obesity.

High respiratory quotient is associated with increases in body weight and fat mass in young adults.

BACKGROUND/OBJECTIVES: Metabolic disturbances, such as reduced rates of fat oxidation (high respiratory quotient (RQ)) or low energy expenditure (low resting metabolic rate (RMR)), may contribute to obesity. The objective was to determine the association between a high RQ or a low RMR and changes in body weight and body composition over 1 year. SUBJECTS/METHODS: We measured RQ and RMR in 341 adults using indirect calorimetry, along with body weight/body composition using dual-energy X-ray absorptiometery, energy expenditure using an arm-based activity monitor and energy intake using dietary recalls. Participants were classified into low, moderate or high RQ and RMR (adjusted for age, sex, race and body composition) groups according to tertiles by sex. Follow-up measurements were completed every 3 months. RESULTS: Individuals with a high RQ had larger gains in body weight and fat mass compared with individuals with a low/moderate RQ at month 3, and increases in fat mass were more than double among individuals with a high RQ at 12 months (1.3±3.0 vs 0.6±3.7 kg, P=0.03). Individuals with a low RMR did not gain more body weight nor fat mass compared with individuals with a moderate/high RMR. CONCLUSION: The primary finding is a high RQ is predictive of gains in body weight and fat mass over a 12-month period among young adults, with changes occurring as soon as 3 months. In addition, a low RMR was not associated with gains in body weight or fat mass over the same period.

Lifestyle intervention in overweight individuals with a family history of diabetes.

OBJECTIVE: To assess the effect of lifestyle intervention over 2 years on changes in weight, coronary heart disease (CHD) risk factors, and incidence of diabetes in overweight individuals with a parental history of diabetes. RESEARCH DESIGN AND METHODS: Participants (n = 154), who were 30-100% over ideal body weight, had one or both parents with diabetes, and were currently nondiabetic, were randomly assigned to 2-year treatments focused on diet (decreasing calories and fat intake), exercise (goal of 1,500 kcal/week of moderate activity), or the combination of diet plus exercise or to a no-treatment control group. Subjects were reassessed at 6 months, 1 year, and 2 years. RESULTS: At 6 months, the groups differed significantly on measures of eating, exercise, and fitness; weight losses in the diet and diet-plus-exercise groups were significantly greater than in the exercise and control conditions. Weight losses were associated with positive changes in CHD risk factors. After 6 months, there was gradual deterioration of behavioral and physiological changes, so that at 2 years, almost no between-group differences were maintained. Differences between groups in risk of developing diabetes were of borderline significance (P = 0.08). Strongest predictors were impaired glucose tolerance at baseline, which was positively related to risk of developing diabetes, and weight loss from baseline to 2 years, which was negatively related; in all treatment groups, a modest weight loss of 4.5 kg reduced the risk of type 2 diabetes by approximately 30% compared with no weight loss. CONCLUSIONS: Although initially successful, the interventions studied here were not effective in producing long-term changes in behavior, weight, or physiological parameters. However, weight loss from 0 to 2 years reduced the risk of developing type 2 diabetes. Since modest weight loss significantly reduced risk of type 2 diabetes, further research is needed to determine how best to increase the percentage of subjects achieving at least a modest weight loss.

The effects of health beliefs on weight loss in individuals at high risk for NIDDM.

OBJECTIVE: To determine whether perceived risk and other health beliefs held by individuals at high risk for developing NIDDM predict weight loss and behavior change during a behavioral weight loss program to reduce the risk of NIDDM. RESEARCH DESIGN AND METHODS: Health beliefs and objective risk factors for diabetes were examined in 154 overweight men and women with a family history of NIDDM. The effects of these factors on adherence, dietary intake, weight loss, and changes in glucose levels were examined in a subset of 79 of these subjects who participated in a 2-year behavioral weight control program. RESULTS: Those subjects who perceived themselves at highest risk of developing diabetes had a stronger family history of the disease and were more likely to be women than subjects considering themselves at more moderate risk. These participants also rated diabetes as a more serious disease, but were less likely to believe that weight loss would lower their risk. None of these health beliefs were related to attendance at meetings, dietary intake, weight loss, or fasting glucose, but higher perceived seriousness predicted larger reductions in BMI at 1 year. Of the objective risk factors for NIDDM, higher baseline BMI predicted larger weight losses throughout the program, and a stronger family history of diabetes was related to greater weight regain after an initial weight loss. CONCLUSIONS: Perceived risk of developing diabetes and other health beliefs did not predict performance in a behavioral weight loss program. These data suggest that efforts to modify health beliefs by educating high-risk individuals about their risk and benefits of weight loss may not be effective in improving long-term weight loss results.

Behavioral science research in diabetes: lifestyle changes related to obesity, eating behavior, and physical activity.

Lifestyle factors related to obesity, eating behavior, and physical activity play a major role in the prevention and treatment of type 2 diabetes. In recent years, there has been progress in the development of behavioral strategies to modify these lifestyle behaviors. Further research, however, is clearly needed, because the rates of obesity in our country are escalating, and changing behavior for the long term has proven to be very difficult. This review article, which grew out of a National Institute of Diabetes and Digestive and Kidney Diseases conference on behavioral science research in diabetes, identifies four key topics related to obesity and physical activity that should be given high priority in future research efforts: 1) environmental factors related to obesity, eating, and physical activity; 2) adoption and maintenance of healthful eating, physical activity, and weight; 3) etiology of eating and physical activity; and 4) multiple behavior changes. This review article discusses the significance of each of these four topics, briefly reviews prior research in each area, identifies barriers to progress, and makes specific research recommendations.

Effects of a very-low-calorie diet and physical-training regimens on body composition and resting metabolic rate in obese females.

Sixty-nine obese females received 90 d of a liquid diet providing 2184 kJ/d in clinical trials. Groups were diet only (C), diet plus endurance exercise (EE), diet plus weight training (WT), or diet plus endurance exercise and weight training (EEWT). Changes in body weight, percent fat, fat weight, and fat-free mass were not different between groups. Declines in resting metabolic rate (RMR) were approximately 7% to approximately 12% of baseline values with no differences among groups. A significant increase in work capacity (approximately 16%) was shown for EEWT. Strength index showed declines of approximately 6% for C and EE and gains of approximately 3% and approximately 10% for EEWT and WT, respectively. These clinical trials did not show advantages of any exercise regimen over diet alone for weight loss, body-composition changes, or declines in RMR. Improvements in work capacity were limited and strength improved in groups that participated in strength training.

Lifestyle physical activity interventions. History, short- and long-term effects, and recommendations.

INTRODUCTION: Lifestyle physical activity interventions have resulted in response to the public health problem of promoting regular amounts of physical activity to the majority of U.S. adults who remain inadequately or completely inactive. These lifestyle interventions allow a person to individualize his/her physical activity programs to include a wide variety of activities that are at least of moderate intensity and to accumulate bouts of these activities in a manner befitting his/her life circumstances. METHODS: We reviewed the history of lifestyle physical activity interventions and defined lifestyle physical activity based on this review. We located 14 studies that met this definition. RESULTS: Lifestyle physical activity interventions are effective at increasing and maintaining levels of physical activity that meet or exceed public health guidelines for physical activity in representative samples of previously sedentary adults and obese children. The majority of these interventions have been delivered by face-to-face contact in small groups, which limits their public health impact. However, a small number of studies demonstrate that these interventions can be delivered by mail and telephone, which may enhance their generalizability. Most of these studies utilized behavior change theories such as Social Cognitive Theory, the Transtheoretical Model, and Behavior Learning to shape the interventions. Lifestyle interventions aimed at modifying the environment, such as signs posted to increase stair climbing, also have been shown to be effective over the short term. CONCLUSIONS: The major issues concerning lifestyle physical activity interventions are: (1) testing their ability to be implemented on a large scale; (2) examining cost-effectiveness for different modes of delivery; and (3) researching the efficacy in populations such as the elderly, minorities, economically disadvantaged, and individuals with concurrent disease. More studies aimed at manipulating the environment to increase physical activity need to be tested over periods of one year or longer. It is possible that lifestyle interventions could be integrated and delivered by new technologies such as interactive computer-mediated programs, telephone, or computer web-based formats. All of these recommended approaches should utilize valid and reliable measures of physical activity and should examine the health effects, particularly on a longitudinal basis. Basic dose-response studies in controlled settings also are needed to help us understand the health effects of accumulated moderate intensity activity.

Weight cycling, psychological health, and binge eating in obese women.

This study examined the relationship between weight cycling and psychological health in 120 obese women. Weight cycling was defined in 2 ways by retrospective self-report: total lifetime weight loss and total number of weight cycles > or = 20 lbs (> or = 9.07 kg). Psychological self-report measures assessed psychiatric symptoms, eating behavior, mood, stress, and perceptions of physical health. Of the 52 associations between weight cycling and psychological parameters, 8 were significant, with the most consistent association being between weight cycling and binge eating. Binge eating was also strongly associated with psychological distress, as found in previous studies. After adjusting for binge eating, however, weight cycling was independently related to only one of the psychological measures: perceived physical health.

Accuracy of self-reported exercise and the relationship with weight loss in overweight women.

PURPOSE: The purpose of this study was to compare self-reported exercise to a more objective measurement of exercise (i.e., Tri-Trac Accelerometer) and to assess whether there is a difference in weight loss between individuals who under- and over-report their exercise. METHODS: Fifty overweight females (BMI = 34.0 +/- 4.2 kg.m-2) who were participating in a behavioral weight control program were included in this study. Subjects were randomly assigned to a long-bout or a short-bout exercise condition, with both groups instructed to exercise 30 min.day-1 on 5 d.wk-1 for a period of 20 wk. The long-bout group was to exercise in one continuous session (e.g., one 30-min session per day), whereas the short-bout group was to divide the exercise into multiple 10-min sessions (e.g., three 10-min sessions per day). Subjects recorded their exercise in a daily exercise log and wore a Tri-Trac accelerometer for a 1-wk period to validate self-reported exercise bouts. RESULTS: Results showed that approximately 45% of the women over-reported the amount of exercise that they performed, and this did not differ between the long-bout and short-bout groups. Women who over-reported their exercise had significantly poorer weight loss across the 20-wk program than women who under-reported their exercise (6.3 +/- 3.6 kg vs 9.4 +/- 5.2 kg). CONCLUSIONS: The results of this study suggest that overweight women who over-report their exercise will have poorer weight loss while enrolled in a behavioral weight loss program compared with others enrolled in the program, and the Tri-Trac Accelerometer may be useful in identifying individuals who inaccurately report the amount of their exercise. The ability to classify individuals as either over- or under-reporters of their exercise may be helpful to weight loss therapists and lead to more successful treatment for obesity.

The accuracy of the TriTrac-R3D accelerometer to estimate energy expenditure.

PURPOSE: This study examined the reliability and validity of the TriTrac-R3D triaxial accelerometer to estimate energy expenditure during various modes of exercise. METHODS: Twenty subjects (age = 21.5+/-3.4 yr; body mass index = 23.3+/-3.6 kg x m(-2)) performed five exercises (treadmill walking, treadmill running, stepping, stationary cycling, and slideboard), with each lasting 20-30 min and workload increased at 10-min intervals. To test the inter-TriTrac reliability, two TriTrac-R3D accelerometers were worn during each exercise period, and to examine validity, a simultaneous measurement of energy expenditure was made using indirect calorimetry (SensorMedics 2900 Metabolic Cart). RESULTS: Results showed a significant correlation between the two TriTrac-R3D accelerometers during all exercises. The difference in estimated energy expenditure between the two accelerometers during the walking, stepping, and slideboard exercises was less than 1 kcal x min(-1) but statistically significant (P<0.05). There was also a significant correlation between energy expenditure estimated by each of the TriTrac-R3D accelerometers and indirect calorimetry during walking, running, stepping, and slideboard exercise (P<0.05). The interaction of Method x Workload was significant (P<0.05) for each exercise, indicating that the TriTrac-R3D underestimates energy expenditure and that the magnitude of this underestimation increases as workload increases. CONCLUSIONS: Therefore, energy expenditure estimated via triaxial accelerometry does not increase with increasing workloads. These results suggest that there are limitations to using triaxial accelerometry to quantify energy expenditure.

American College of Sports Medicine position stand. Appropriate intervention strategies for weight loss and prevention of weight regain for adults.

In excess of 55% of adults in the United States are classified as either overweight (body mass index = 25-29.9 kg.m(-2)) or obese (body mass index > or = 30 kg.m(-2)). To address this significant public health problem, the American College of Sports Medicine recommends that the combination of reductions in energy intake and increases in energy expenditure, through structured exercise and other forms of physical activity, be a component of weight loss intervention programs. An energy deficit of 500-1000 kcal.d-1 achieved through reductions in total energy intake is recommended. Moreover, it appears that reducing dietary fat intake to <30% of total energy intake may facilitate weight loss by reducing total energy intake. Although there may be advantages to modifying protein and carbohydrate intake, the optimal doses of these macronutritents for weight loss have not been determined. Significant health benefits can be recognized with participation in a minimum of 150 min (2.5 h) of moderate intensity exercise per week, and overweight and obese adults should progressively increase to this initial exercise goal. However, there may be advantages to progressively increasing exercise to 200-300 min (3.3-5 h) of exercise per week, as recent scientific evidence indicates that this level of exercise facilitates the long-term maintenance of weight loss. The addition of resistance exercise to a weight loss intervention will increase strength and function but may not attenuate the loss of fat-free mass typically observed with reductions in total energy intake and loss of body weight. When medically indicated, pharmacotherapy may be used for weight loss, but pharmacotherapy appears to be most effective when used in combination with modifications of both eating and exercise behaviors. The American College of Sports Medicine recommends that the strategies outlined in this position paper be incorporated into interventions targeting weight loss and the prevention of weight regain for adults.