Impact of sleep, screen time, depression and stress on weight change in the intensive weight loss phase of the LIFE study.

BACKGROUND: The LIFE study is a two-phase randomized clinical trial comparing two approaches to maintaining weight loss following guided weight loss. Phase I provided a nonrandomized intensive 6-month behavioral weight loss intervention to 472 obese (body mass index 30-50) adult participants. Phase II is the randomized weight loss maintenance portion of the study. This paper focuses on Phase I measures of sleep, screen time, depression and stress. METHODS: The Phase I intervention consisted of 22 group sessions led over 26 weeks by behavioral counselors. Recommendations included reducing dietary intake by 500 calories per day, adopting the Dietary Approaches to Stop Hypertension (DASH) dietary pattern and increasing physical exercise to at least 180 min per week. Measures reported here are sleep time, insomnia, screen time, depression and stress at entry and post-weight loss intervention follow-up. RESULTS: The mean weight loss for all participants over the intensive Phase I weight loss intervention was 6.3 kg (s.d. 7.1). Sixty percent (N=285) of participants lost at least 4.5 kg (10 lbs) and were randomized into Phase II. Participants (N=472) attended a mean of 73.1% (s.d. 26.7) of sessions, completed 5.1 (s.d. 1.9) daily food records/week, and reported 195.1 min (s.d. 123.1) of exercise per week. Using logistic regression, sleep time (quadratic trend, P=0.030) and lower stress (P=0.024) at entry predicted success in the weight loss program, and lower stress predicted greater weight loss during Phase I (P=0.021). In addition, weight loss was significantly correlated with declines in stress (P=0.048) and depression (P=0.035). CONCLUSION: Results suggest that clinicians and investigators might consider targeting sleep, depression and stress as part of a behavioral weight loss intervention.

Effects of aquifer heterogeneity and reaction mechanism uncertainty on a reactive barrier.

This paper addresses impacts of aquifer heterogeneity and reaction mechanism uncertainty on permeable reactive barrier (PRB) performance and describes modeling tools and preliminary guidelines for risk-based design of reactive barriers at heterogeneous sites. A braided stream aquifer was generated stochastically, using a fixed correlation structure and four levels of variability in the hydraulic conductivity field. A vertical, homogeneous barrier was placed in the aquifer. Based on a deterministic design, the size of the PRB for uniform conditions was considered conservative (factor of safety=3.3). Monte Carlo simulation was used to model cis 1,2-DCE reduction by iron metal with uncertainty in the reaction mechanism rate constants. These results were combined with flow and particle tracking results to predict the spatial distribution and flow-averaged concentrations of cis 1,2-DCE and vinyl chloride at the exit face of the PRB. Evaluated on a risk basis, the deterministic design method was found to be unconservative for more heterogeneous aquifers. Uncertainty in the reaction mechanism accentuated the negative effects of aquifer heterogeneity. Several compensating factors that may reduce the vulnerability of reactive barriers to aquifer heterogeneity are discussed.