James D. LeCheminant

Minimal resistance training improves daily energy expenditure and fat oxidation.

UNLABELLED Long-term resistance training (RT) may result in a chronic increase in 24-h energy expenditure (EE) and fat oxidation to a level sufficient to assist in maintaining energy balance and preventing weight gain. However, the impact of a minimal RT program on these parameters in an overweight college-aged population, a group at high risk for developing obesity, is unknown. PURPOSE We aimed to evaluate the effect of 6 months of supervised minimal RT in previously sedentary, overweight (mean +/- SEM, BMI = 27.7 +/- 0.5 kg x m(-2)) young adults (21.0 +/- 0.5 yr) on 24-h EE, resting metabolic rate (RMR), sleep metabolic rate (SMR), and substrate oxidation using whole-room indirect calorimetry 72 h after the last RT session. METHODS Participants were randomized to RT (one set, 3 d x wk(-1), three to six repetition maximums, nine exercises; N = 22) or control (C, N = 17) groups and completed all assessments at baseline and at 6 months. RESULTS There was a significant (P < 0.05) increase in 24-h EE in the RT (527 +/- 220 kJ x d(-1)) and C (270 +/- 168 kJ x d(-1)) groups; however, the difference between groups was not significant (P = 0.30). Twenty-four hours of fat oxidation (g x d(-1)) was not altered after RT; however, reductions in RT assessed during both rest (P < 0.05) and sleep (P < 0.05) suggested increased fat oxidation in RT compared with C during these periods. SMR (8.4 +/- 8.6%) and RMR (7.4 +/- 8.7%) increased significantly in RT (P < 0.001) but not in C, resulting in significant (P < 0.001) between-group differences for SMR with a trend for significant (P = 0.07) between-group differences for RMR. CONCLUSION A minimal RT program that required little time to complete (11min per session) resulted in a chronic increase in energy expenditure. This adaptation in energy expenditure may have a favorable impact on energy balance and fat oxidation sufficient to assist with the prevention of obesity in sedentary, overweight young adults, a group at high risk for developing obesity.

A Comparison of Meal Replacements and Medication in Weight Maintenance after Weight Loss

Objective: To compare the use of meal replacements or medication during weight maintenance subsequent to weight loss using a very low-energy diet (VLED) in overweight or obese adults. Design: Participants followed a liquid VLED of 2177 kJ for 12 weeks followed by 4 weeks of re-orientation to solid foods. Participants were randomized at week 16 to receive either meal replacements or Orlistat both combined with a structured meal plan containing an energy value calculated to maintain weight loss. Subjects: Sixty-four women (age = 49.9 ± 10 y, weight = 101.6 ± 17.1 kg, height = 164.9 ± 6.0 cm, BMI = 36.7 ± 5.4 kg/m2) and 28 men (age = 53.7 ± 9.6 y, weight = 121.8 ± 16.0 kg, height = 178.7 ± 5.6 cm, BMI = 37.8 ± 4.9 kg/m2) completed a 1 year weight management program. Behavioral weight management clinics included topics on lifestyle, physical activity (PA), and nutrition. Participants met for 90 min weekly for 26 weeks, and then biweekly for the remaining 26 weeks. Outcomes: Minutes of PA, fruits and vegetables (FV), and pedometer steps were recorded on a daily basis and reported at each group meeting. Body weight was obtained at each group meeting. Results: During VLED, the MR group decreased body weight by 22.8 ± 6.1 kg and the Orlistat group decreased body weight by 22.3 ± 6.1 kg. During weight maintenance, there was no significant group by time interaction for body weight, PA, FV consumption, or pedometer steps. At week 16, the meal replacement group had a body weight of 85.4 ± 14.3 kg that increased to 88.1 ± 16.5 kg at 52 weeks (p < 0.05). At week 16, the Orlistat group had a body weight of 85.7 ± 17.9 kg that increased to 88.5 ± 20.3 kg at 52 weeks (p < 0.05). Conclusions: Subsequent to weight loss from a VLED, meal replacements and Orlistat treatments were both effective in maintaining weight significantly below baseline levels over a 52 week period of time. Meal replacements may be a viable alternative strategy to medications for weight maintenance.

Weight Loss-Induced Alterations in Serum Markers of Bone Turnover Persist during Weight Maintenance in Obese Men and Women

Objective: Moderate weight loss alters bone turnover and reduces bone mineral density in overweight men and women. However, it is not known whether bone turnover is normalized during weight maintenance postweight loss. Thus, the objective of the present study was to examine changes in serum bone turnover markers during 9 months of weight maintenance following weight reduction on a very low-energy diet (VLED) in obese men and women. Methods: Thirty-seven men (n  =  13) and women (n  =  24) aged 50 ± 9.8 years underwent 3 months of weight reduction on a VLED (∼500 kcal/d) followed by 9 months on either a low-carbohydrate or low-fat weight maintenance diet (∼1600 kcal/d). Concentrations of osteocalcin (OC) and C-terminal peptide of type I collagen (CTX) in serum were measured using enzyme-linked immunosorbent assay at baseline and at months 3, 6, and 12. Serum parathyroid (PTH) concentrations were measured using a chemiluminescent immunoassay at all 4 time points. Data were analyzed using a 3-factor-repeated measures analysis of variance. Results: Average weight loss was 19% ± 3% and, during the 9-month weight maintenance period, average weight gain was ∼3%, with no differences due to diet composition. Serum concentrations of OC and CTX significantly increased after weight reduction and remained elevated during weight maintenance. Serum PTH was reduced after weight loss. Percent changes in OC and CTX were correlated during weight maintenance (r  =  −0.437, p  =  0.008), but not during weight loss. Percent changes in CTX and body weight were negatively correlated during weight loss (r  =  −0.474, p  =  0.003) and maintenance (r  =  −0.455, p  =  0.006). Conclusions: Weight loss induced via a VLED may result in an imbalance between bone formation and resorption and accelerate remodeling. The deleterious effect of energy restriction on bone remodeling rate appears to persist during weight maintenance.

Neural response to pictures of food after exercise in normal-weight and obese women.

PURPOSE This study examined the effect of a bout of moderate-to-vigorous (MV) exercise on the neural response to pictures of food (used to index food motivation) in normal-weight and obese women. Secondary outcomes included energy intake and physical activity (PA) over 24 h. METHODS Using a crossover design, 18 normal-weight and 17 obese women completed a morning-time, 45-min exercise bout (treadmill at 3.8 mph; 0% grade) and were subsequently followed for 24 h. This was counterbalanced by a control day with no exercise bout. To assess the effect of exercise on food motivation, participants were shown pictures of food and flowers (control) after exercise. Neural activity was concurrently monitored using electroencephalogram for the late positive potential (LPP) component of the event-related potential (ERP) and compared with the LPP response on the nonexercise day. After testing, weighed food records were kept for the duration of each day. PA was monitored, via accelerometry, over each day. RESULTS There was not a significant body mass index (BMI) group × exercise condition × picture-type interaction for LPP amplitude; however, when participants were pooled, the exercise condition resulted in lower LPP amplitude waveforms in response to food pictures than the nonexercise condition (F = 4.25, P = 0.048). There were no differences in energy or macronutrient intake (P > 0.05). The exercise condition resulted in significantly more PA than the nonexercise condition, and there was a significant BMI group × exercise condition interaction for MV PA (F = 4.48, P = 0.043) with obese women showing less MV PA. CONCLUSIONS A bout of MV exercise decreases neurologically determined food motivation (i.e., the LPP event-related potential), but the effect of BMI is unclear. In addition, a morning-time exercise bout significantly increases 24-h PA; 24-h MV PA differed according to BMI.

A Prospective Study of Physical Activity Intensity and Change in Adiposity in Middle-Aged Women

Purpose. To determine the extent to which objectively measured intensity of physical activity (PA) predicts change in body fat (BF%) in women. Design. Prospective cohort study of PA intensity and body composition in middle-aged women. Setting. The study took place in a metropolitan Mountain West community. Subjects. Two hundred and twenty-eight women participated in two assessment periods separated by 20 months. Measures. Each assessment period consisted of seven consecutive days of monitoring, followed by body composition testing. Analysis. The general linear model using partial correlations and Mantel-Haenszel χ2 tests were performed. Results. At baseline and follow-up, women who participated in vigorous PA were leaner than women who participated in moderate or light PA (p < .05). Longitudinal results indicated that a greater proportion of women who decreased PA intensity over the 20 months also increased BF% (66%), compared to participants who increased or maintained PA intensity (47%) (p < .05). Conclusions. PA intensity seems to play a role in long-term weight maintenance. Reducing PA intensity increases the risk of BF% gain in women. Efforts to help women maintain PA intensity along with other weight management strategies may prove beneficial in preventing unwanted body fat gain in middle-aged women.

Reporting quality of randomized trials in the diet and exercise literature for weight loss

BackgroundTo adequately assess individual studies and synthesize quantitative research on weight loss studies, transparent reporting of data is required. The authors examined the reporting quality of randomized trials in the weight loss literature, focusing exclusively on subject characteristics as they relate to enrollment, allocation, and follow-up.MethodsAn extensive literature review, which included a computerized search of the MEDLINE database, manual searches of bibliographic references, and cross-referencing of 92 review articles was conducted. A checklist, based on CONSORT recommendations, was used to collect information on whether or not authors reported age, gender, co-morbid disease, medication use, race/ethnicity, and postmenopausal status. Also tracked was whether or not initial and final sample size was reported and stratified by gender.ResultsOf 604 possible articles, 231 articles met eligibility criteria. Important subject characteristics were not reported as the following breakdown indicates: age (11%), gender (4%), race/ethnicity (86%), co-morbid disease states (34%), and medication use (92%). Additionally, 21% of articles failed to report initial sample size by gender while 69% neglected to report final sample size by gender.ConclusionInadequate reporting can create difficulties with interpretation and can lead to biased results receiving false credibility. The quality of reporting for weight loss studies needs considerable improvement.

Author contacts for retrieval of data for a meta-analysis on exercise and diet restriction.

OBJECTIVES The mode of contact and response levels of authors who had been asked to provide missing or incomplete data for a systematic review on diet and exercise interventions for weight loss was examined. METHODS We contacted authors by electronic mail, letter, or both. Survival analyses were performed with the Kaplan-Meier method to determine differences in the proportion of responders over time among the different modes of contact and to determine whether response rates differed between authors from the United States and those from other countries. Logistic regression was used to determine whether the number of items requested and publication date influenced the likelihood of response. RESULTS Two hundred forty-one (39.9 percent) studies had missing or incomplete data (e.g., sample size, age, caloric restriction, exercise amount, and so on). We were unable to locate ninety-five authors (39.4 percent). Of the remaining authors, forty-six authors (31.5 percent) responded to information requests. Time to respond differed by contact method (p < .05): e-mail (3 +/- 3 days), letter (27 +/- 30 days), and both (13 +/-12 days). Response rates from U.S. authors did not differ from those of other countries. CONCLUSIONS Our study suggests poor success in the acquisition of essential information. Given considerable time and resources, weight loss studies require improved reporting standards to minimize the relatively unsuccessful attempt to contact authors for important and necessary information.

Restricting night-time eating reduces daily energy intake in healthy young men: a short-term cross-over study

Few experimental data are available to support the notion that reducing night-time eating changes total daily energy intake (EI) or body weight in healthy adults. The present study primarily examined the short-term effect of night eating restriction (NER) on daily EI in healthy young men. It secondarily examined body weight and moods associated with NER. Using a cross-over design, twenty-nine men (20·9 (sd 2·5) years; 24·4 (sd 2·5) kg/m²) initiated a 2-week NER intervention (elimination of EI from 19.00 to 06.00 hours) and a 2-week control condition, counterbalanced and separated by a 1-week washout period. EI and macronutrient intake were assessed using computerised, multiple-pass 24 h food recalls, body weight via a digital scale and mood using the Profile of Mood States survey. Of the twenty-nine participants, twenty-seven (93 %) completed all aspects of the study. During the NER condition, the participants consumed less total energy per d than during the control condition (10 125 v. 11 146 kJ/d; F= 6·41; P= 0·018). During the NER condition, no energy was reported consumed between 19.00 and 06.00 hours; however, during the control condition, the energy intake of participants was 2920 (sd 1347) kJ/d between 19.00 and 06.00 hours. There was a significant difference in weight change between the NER (-0·4 (sd 1·1) kg) and control (+0·6 (sd 0·9) kg) conditions (F= 22·68; P< 0·001). Differences in total mood score or mood subscales between the NER and control conditions were not apparent (P>0·05). These findings provide support for NER decreasing short-term EI in healthy young men.

Obesity increases risk of declining physical activity over time in women: a prospective cohort study

Research indicates that risk of obesity increases as physical activity (PA) decreases; however, the reciprocal effect has been rarely studied. The present investigation was conducted to determine the contribution of obesity on objectively measured PA over 20 months.

Test-Retest Reliability of the Bod Pod: The Effect of Multiple Assessments

The Bod Pod uses air-displacement plethysmography to estimate body fat percentage (BF%). This study was designed to assess the test-retest reliability of the Bod Pod. The study included 283 women (M age =41.0 yr., SD = 3.0). Each participant was tested at least twice in the Bod Pod. Results showed no significant mean difference between the test and the retest. The intraclass correlation coefficient (ICC) was .991. However, the absolute value of the initial trial differences (absolute mean difference) was .96 (SD = .90). A third assessment of BF% was taken when the initial trial difference was greater than 1 percentage point, and the two closest values were compared. This strategy resulted in a significant decrease in the absolute mean difference, from .96 to .55 percentage point, and ICC increased to .998. The Bod Pod appears to measure body fat percentage reliably; however, findings suggest that multiple trials may be necessary to detect small treatment effects.