Addressing the psychology of weight loss and maintenance: A feasibility study of the Skills for weight loss and Maintenance weight management programme

OBJECTIVES

Building on prior theory, we aimed to evaluate the feasibility and acceptability of integrating novel, weight loss maintenance strategies into existing weight management programmes. We also piloted recruitment and data collection procedures for future research.

DESIGN

Two phases of action research nested within a single-arm feasibility study. The intervention was refined between phases using feedback from intervention fidelity analysis and qualitative exploration of patient and provider experiences. Changes in outcomes were assessed up to 18 months post-baseline.

METHODS

One hundred adults with a mean body mass index of 37 kg/m2 were offered the Skills for weight loss and Maintenance (SkiM) intervention. This included existing weight management programme content and additional weight loss maintenance techniques delivered fortnightly for 6 months in local community centres to groups of 11-15 people.

RESULTS

Of the 100 participants, 65%, 58% and 56% provided data at 7, 12 and 18 months. Across both phases, the mean initial weight loss was 4.2 kg (95% CI: 2.4-5.9) and 3.1 kg at 18 months (95% CI: .8-5.5). In Phase 2, we observed better weight loss maintenance (.5 kg [13.2%] regain from 7 to 18 months, vs. 1.7 kg [36.2%] in Phase 1). Variation in outcomes, high early dropout rates and qualitative feedback indicated that, although delivery of the intervention and trial procedures was feasible and acceptable, there was scope to refine the intervention to engage a wider range of participants. Intervention fidelity was acceptable, particularly in Phase 2.

CONCLUSIONS

The SkiM intervention seems promising, but more research is needed to improve recruitment and retention prior to further evaluation.

The concentration-dependent aggregation of Ag NPs induced by cystine

Cystine is widely used in cell culture media. Cysteine, the reduced form of cystine, is widely used to scavenge dissolved Ag in eco-toxicological studies to differentiate dissolved vs. nanoparticle uptake and toxicity. However, little is known about the impact of cysteine and cystine on the aggregation behavior of Ag NPs, in particular as a function of Ag NP concentration. Herein, we investigate how cystine (0-300μM) affects the stability of citrate-, polyvinylpyrrolidone-, and polyethylene glycol-coated silver nanoparticles (cit-Ag NPs, PVP-Ag NPs and PEG-Ag NPs, respectively) with and without Suwannee River fulvic acid (SRFA) as a function of Ag NPs concentration using UV-vis spectroscopy at environmentally and ecotoxicologically relevant Ag NP concentrations (ca. 125-1000μgL(-1)). The results demonstrate, for the first time, the concentration-dependent aggregation of cit-Ag NPs in the presence of cystine with a shift in the critical coagulation concentration (CCC) to lower cystine concentrations at lower cit-Ag NP concentrations. At the highest cit-Ag NP concentration (1000μgL(-1)), reaction limited aggregation was only observed and no CCC was measured. SRFA slowed the aggregation of cit-Ag NPs by cystine and aggregation occurred in reaction limited aggregation (RLA) regime only. No CCC value was measured in the presence of SRFA. Cystine replaces citrate, PVP and PEG coatings, resulting in aggregation of both electrostatically and sterically stabilized Ag NPs. These findings are important in understanding the factors determining the behavior of Ag NPs in cell culture media. Also due to the similarity between cystine and cysteine, these results are important in understanding the uptake and toxicity of Ag NPs vs. Ag ions, and suggest that the reduction of the toxicity of Ag NPs in the presence of cysteine could be due to a combined effect of scavenging Ag(+) ions and Ag NP aggregation in the presence of cysteine.

Subject-specific computational simulation of left ventricular flow based on magnetic resonance imaging

A detailed investigation of left ventricle (LV) flow patterns could improve our understanding of the function of the heart and provide further insight into the mechanisms of heart failure. This study presents patient-specific modelling with magnetic resonance imaging (MRI) to investigate LV blood flow patterns in normal subjects. In the study, the prescribed LV wall movements based on the MRI measurements drove the blood flow in and out of the LV in computational fluid dynamics simulation. For the six subjects studied, the simulated LV flow swirls towards the aortic valve and is ejected into the ascending aorta with a vertical flow pattern that follows the left-hand rule. In diastole, the inflow adopts a reasonably straight route (with no significant secondary flow) towards the apex in the rapid filling phase with slight variations in the jet direction between different cases. When the jet reaches about two thirds of the distance from the inflow plane to the apex, the blood flow starts to change direction and swirls towards the apex. In the more slowly filling phase, a centrally located jet is evident with vortices located on both sides of the jet on an anterior—posterior plane that passes through the mitral and aortic valves. In the inferior—superior plane, a main vortex appears for most of the cases in which an anticlockwise vortex appears for three cases and a clockwise vortex occurs for one case. The simulated flow patterns agree well qualitatively with MRI-measured flow fields.

The influence of inflow boundary conditions on intra left ventricle flow predictions

The combination of computational fluid dynamics (CFD) and magnetic resonance imaging (MRI) offers a promising tool that enables the prediction of blood flow patterns in subject-specific cardiovascular models. The influence of the model geometry on the accuracy of the simulation is well recognized. This paper addresses the impact of different boundary conditions on subject-specific simulations of left ventricular (LV) flow. A novel hybrid method for prescribing effective inflow boundary conditions in the mitral valve plane has been developed. The detailed quantitative results highlight the strengths as well as the potential pitfalls of the approach.

Dual contrast TrueFISP imaging for left ventricular segmentation

Based on varying tissue contrasts at different RF flip angles, a new TrueFISP imaging strategy for cardiac function measurement is presented. A single breath-hold dual RF flip angle cine multi-slice TrueFISP imaging sequence was implemented which provides a significant increase in signal contrast between blood and myocardium. The increase in image contrast combined with different characteristics in RF response facilitates the delineation of cardiovascular borders. Based on this imaging strategy it is demonstrated how a simple 2D histogram clustering algorithm can be used for the fully automatic segmentation of the left ventricular (LV) blood pool. The method is validated with data acquired from 10 asymptomatic subjects, and the results are shown to be comparable to that of manual delineation by experienced observers.

Airblast TNT equivalence for a range of commercial blasting explosives

Results are reported from a programme of work undertaken by the UK Health and Safety Executive to investigate the airblast produced by commercial sector explosives having velocities of detonation (VoD) in the range 2000-8200 m s(-1). The data produced will be useful in evaluating the blast hazards of such explosives in industrial circumstances and also as a means of assessing post-accident damage. All of the solid explosive materials studied produced blast waves which ramped up into shock-wave form close to the point of initiation. The dependence of peak overpressure and positive phase impulse on scaled distance is presented and compared to that of TNT. The TNT equivalence (TNT(e)) technique is shown to be applicable to solid phase explosives with a wide range of VoD, although the precise values of TNT(e) vary with distance.

Fire and explosion hazards to flora and fauna from explosives

Deliberate or accidental initiation of explosives can produce a range of potentially damaging fire and explosion effects. Quantification of the consequences of such effects upon the surroundings, particularly on people and structures, has always been of paramount importance. Information on the effects on flora and fauna, however, is limited, with probably the weakest area lying with fragmentation of buildings and their effects on different small mammals. Information has been used here to gain an appreciation of the likely magnitude of the potential fire and explosion effects on flora and fauna. This is based on a number of broad assumptions and a variety of data sources including World War II bomb damage, experiments performed with animals 30-40 years ago, and more recent field trials on building break-up under explosive loading.