Control of crystallization in supramolecular soft materials engineering

As one class of the most important supramolecular functional materials, gels formed by low molecular weight gelators (LMWGs) have many important applications. The key important parameters affecting the in-use performance of a gel are determined by the hierarchical fiber network structures. Fiber networks consisting of weakly interacting multiple domains are commonly observed in gels formed by LMWGs. The rheological properties, particularly the elasticity, of a gel with such a fiber network are weak due to the weak interactions between the individual domains. As achieving desirable rheological properties of such a gel is practically relevant, in this work, we demonstrate the engineering of gels with such a type of fiber network by controlling crystallization of the gelator. Two example gels formed by a glutamic acid derivative in a non-ionic surfactant Tween 80 and in propylene glycol were engineered by controlling the thermodynamic driving force for crystallization. For a fixed gelator concentration, the thermodynamic driving force was manipulated by controlling the temperature for fiber crystallization. It was observed that there exists an optimal temperature at which a gel with maximal elasticity can be fabricated. This will hopefully provide guidelines for producing high performance soft materials by engineering their fiber network structures.

Association of birth weight and current body size to blood pressure in female twins

It has been proposed that low birth weight is associated with high levels of blood pressure in later life. The aim of this study was to assess the relationship of blood pressure to birth weight and current body size during growth and adulthood. A total of 711 female multiple births, with one group of 244 in their growth phase mean age 12.0 (2.3)(SD) years and the other of 467 adults (mean age 35.2 (12.6) years), had height, weight and both systolic (SBP) and diastolic (DBP) blood pressures measured, and self-reported their birth weight. Regression analyses were performed to assess the cross-sectional and within-pair associations of blood pressure to birth weight, with and without adjustments for current body size. Within-pair analysis was based on 296 twin pairs. Cross-sectionally, a reduction in birth weight of 1 kg was associated with 2 to 3 mm Hg higher age-adjusted SBP, which was of marginal significance and explained about 2% of the population variance. Adjustment for body mass index did not significantly change this association. Within-pair analyses found no association between birth weight and SBP or DBP,even after adjusting for current body size. After age, current body size was the strongest predictor of systolic BP. The weak association of blood pressure to birth weight cross-sectionally is of interest, but any within-pair effect of birth weight on blood pressure must be minimal compared with the effect of current body size.

Self-esteem and negative affect as moderators of sociocultural influences on body dissatisfaction, strategies to decrease weight and strategies to increase muscles among adolescent boys and girls

The study was conducted to examine the impact of sociocultural influences and the moderating role of self-esteem and negative affect on body dissatisfaction and body change strategies for both adolescent boys and girls. Surveys designed to assess body dissatisfaction, body change strategies to decrease weight and increase muscles, perceived sociocultural pressures to lose weight and increase muscles, self-esteem and negative affect were administered to 587 boys and 598 girls aged between 11 and 15 years. The majority of respondents were from Anglo-Australian backgrounds (83%) with the remainder being from Asian and European non-English-speaking backgrounds. The sociocultural influences were found to significantly predict body dissatisfaction and body change strategies for both boys and girls. However, in the case of boys, self-esteem was found to moderate the impact of the sociocultural influences in predicting body change strategies. It was primarily the boys with low self-esteem who were more affected by the sociocultural pressures whereas the girls were affected independently of their self-esteem. Negative affect was also found to play a moderating role on some of the sociocultural influences in predicting strategies to increase muscles. Both boys and girls with higher levels of negative affect were more likely to be affected by sociocultural messages directed at increasing muscles. The results from the present study demonstrate that as well as examining the direct influence of sociocultural pressures, it is also important to examine how these may be moderated by self-esteem and negative affect.

Body image, strategies to change muscles and weight, and puberty. Do they impact on positive and negative affect among adolescent boys and girls?

The purpose of this study was to examine the impact of strategies to both decrease weight and increase muscle tone on negative (depression, anxiety) and positive affect among adolescent males and females. The respondents were 1185 adolescents (587 males, 598 females) who were enrolled in grades 7 and 9 (mean age for MALES=13.22 years; mean age for FEMALES=13.21 years). Respondents completed the Body Image and Body Change Inventory that assessed body image satisfaction, body image importance, body change strategies to decrease weight, body change strategies to increase muscle tone, and food supplements. Respondents also completed the Pubertal Development Scale, the depression and anxiety scales of the Depression Anxiety and Stress Scale, and the positive affect items from the Positive and Negative Affect Scale. Structural equation modelling was used to determine how body satisfaction and importance, body change strategies, and puberty impacted on depression, anxiety, and positive affect. The results demonstrated that for both boys and girls, there was a strong association between body change strategies and negative affect. For boys, body dissatisfaction did not predict negative affect, although this was a strong predictor for girls. Body change strategies did not strongly predict positive affect for either boys or girls, although body image satisfaction was a strong predictor for both genders. The implications of these findings for obtaining a better understanding of the role of pubertal development, body image, and body change strategies in predicting positive and negative affect among adolescent males and females are discussed.

Beliefs about the causes of weight change in the Australian population

OBJECTIVE: To describe self-reported weight change and beliefs about the causes of weight change and to examine whether these vary by sex and weight status.
DESIGN: This cross-sectional population study examined data from the 1995 Australian National Health and Nutrition Surveys.
SUBJECTS: A total of 10 624 randomly-selected adults provided data.
MEASURES: Objectively measured height and weight, perceptions of current weight status, self-reported weight change over the past year, and reasons for weight change.
RESULTS: Thirty-five percent of participants reported a weight gain in the last 12 months, with females, and those already overweight more likely to report a recent increase in weight. Approximately one in five participants reported a recent weight loss. Those who had recently gained weight were more likely to perceive themselves as overweight regardless of actual weight status. Commonly reported reasons for weight gain included a change in physical activity level (52% males and 35% females) and a change in the amount of food/drink consumed (30% males, 27% females). Similar reasons were given for weight loss.
CONCLUSIONS: Findings of widespread reported weight gain, particularly among those already overweight, suggest Australia's obesity epidemic may be worsening. Strategies are urgently required to better inform individuals about the factors impacting on their weight in order to prevent further weight gain.

Associations of physical activity with body weight and fat in men and women

OBJECTIVE: Increasing physical activity is strongly advocated as a key public health strategy for weight gain prevention. We investigated associations of leisure-time physical activity (LTPA) and occupational/domestic physical activity with body mass index (BMI) and a skinfold-derived index of body fat (sum of six skinfolds), among normal-weight and overweight men and women.

DESIGN: Analyses of cross-sectional self-report and measured anthropometric data.

SUBJECTS: A total of 1302 men and women, aged 18-78 y, who were part of a randomly selected sample and who agreed to participate in a physical health assessment.

MEASUREMENTS: Self-report measures of physical activity, measured height and weight, and a skinfold-derived index of body fatness.

RESULTS: Higher levels of LTPA were positively associated with the likelihood of being in the normal BMI and lower body fat range for women, but few or no associations were found for men. No associations were found between measures of occupational/domestic activity and BMI or body fat for men or women.

CONCLUSION: By using a skinfold sum as a more direct measure of adiposity, this study extends and confirms the previous research that has shown an association between BMI and LTPA. Our results suggest gender differences in the relationship of leisure-time physical activity with body fatness. These findings, in conjunction with a better understanding of the causes of such differences, will have important public health implications for the development and targeting of weight gain prevention strategies.

Comparison of brood size and juvenile weight between a blue strain and normal-coloured strains of the Australian freshwater crayfish Cherax Destructor Clark (Decapoda: Parastacidae)

A blue strain of the yabby Cherax destructor albidus was compared to two normal-coloured strains of C. d. destructor and C. d. albidus for brood size and juvenile weight. Reproductive performance of the blue strain was found to be significantly poorer than the two normal-coloured strains. Similarly, the weight of newly independent juveniles was also found to be significantly lower for the blue strain. No differences were detected between the two normal-coloured strains in either reproductive performance or size of newly independent juveniles. The phenotypic differences between the blue strain and normal-coloured strains are most likely genetic. However, further studies are needed to investigate whether these differences are due to pleiotropy or inbreeding effects.

Who does not gain weight? Prevalence and predictors of weight maintenance in young women

OBJECTIVE: To investigate the prevalence and predictors of weight maintenance over time in a large sample of young Australian women.

DESIGN: This population study examined baseline and 4 y follow-up data from the cohort of young women participating in the Australian Longitudinal Study on Women's Health.

SUBJECTS: A total of 8726 young women aged 18-23 y at baseline.

MEASURES: Height, weight and body mass index (BMI); physical activity; time spent sitting; selected eating behaviours (eg dieting, disordered eating, takeaway food consumption); cigarette smoking, alcohol consumption; parity; and sociodemographic characteristics.

RESULTS: Only 44% of the women reported their BMI at follow-up to be within 5% of their baseline BMI (maintainers); 41% had gained weight and 15% had lost weight. Weight maintainers were more likely to be in managerial or professional occupations; to have never married; to be currently studying; and not to be mothers. Controlling for sociodemographic factors, weight maintainers were more likely to be in a healthy weight range at baseline, and to report that they spent less time sitting, and consumed less takeaway food, than women who gained weight.

CONCLUSIONS: Fewer than half the young women in this community sample maintained their weight over this 4 y period in their early twenties. Findings of widespread weight gain, particularly among those already overweight, suggest that early adulthood, which is a time of significant life changes for many women, may be an important time for implementing strategies to promote maintenance of healthy weight. Strategies which encourage decreased sitting time and less takeaway food consumption may be effective for encouraging weight maintenance at this life stage.

The role of puberty, media and popularity with peers on strategies to increase weight, decrease weight and increase muscle tone among adolescent boys and girls

The present study was concerned with the impact of pubertal development, relationships with peers and perceived pressure from the media on body dissatisfaction and body change behaviors among adolescent boys and girls. In particular, the study investigated the underresearched area of strategies to increase weight and muscle. The exploration of body change strategies among adolescent boys has been a neglected area of research. Methods: Respondents were 1185 adolescents (527 males, 598 females) who were enrolled in Grades 7 and 9. Participants completed measures of pubertal development, media and peer influence, body dissatisfaction and strategies to lose weight, increase weight and to increase muscle. Results: The findings demonstrated that girls were more likely than boys to adopt strategies to lose weight, whereas boys were more likely to adopt strategies to increase muscle tone (but not weight). For boys in both Years 7 and 9, the main predictors of body change strategies were puberty and, to a lesser extent, perceived popularity with peers. The major influences for Years 7 and 9 girls were puberty and the media, but these mainly focused on weight loss. For Year 9 girls, perceived popularity with opposite-sex peers also predicted body dissatisfaction and strategies to increase muscle tone. Conclusion: The implications of these findings for understanding factors related to a range of body change strategies for adolescent boys and girls are discussed.

Preventive strategies against weight gain and obesity

A well-resourced, comprehensive, population-based set of strategies is needed to
attenuate and eventually reverse the current trends of increasing obesity prevalence
now apparent in most countries. The Epidemiological Triad (host, vector,
environment) has proven to be a robust model for other epidemics and is applied
to obesity. Host-based strategies are primarily educational and these tend to
be most effective among people with higher incomes and higher educational
attainment. The main vectors for a high-energy intake are energy-dense foods and
drinks and large portion sizes and, for low energy expenditure, machines that
promote physical inactivity. Vector-based strategies that alter food formulation
can have a significant impact, particularly through influencing common, highvolume
foods. The increasingly ‘obesogenic’ environments are probably the main
driving forces for the obesity epidemic. There are many environmental strategies
that can influence the physical, economic, policy or socio-cultural environments,
but the evidence base for these potentially powerful interventions is small.
Children should be the priority population for interventions, and improving the
general socio-economic conditions for disadvantaged, marginalized or poor population
sectors is also a central strategy for obesity prevention. The key settings
for interventions are schools, homes, neighbourhoods, primary health care services
and communities. The key macroenvironments for interventions are the
transport and infrastructure sector, the media and the food sector.

Nicotine treatment decreases food intake and body weight via a leptin-independent pathway in Psammomys obesus

It has been reported previously that leptin may be involved in nicotine's ability to reduce body weight. Our aim was to investigate whether the anorexic action of nicotine is related to the actions of leptin by utilizing lean leptin-sensitive and obese leptin-resistant Psammomys obesus. Lean and obese P. obesus were assigned to receive nicotine sulphate at 6, 9 or 12 mg/day or saline (control) for 9 days (n = 6-10 in each group), administered using mini-osmotic pumps. Food intake, body weight, plasma leptin concentrations, plasma insulin and blood glucose were measured at baseline and throughout the study period. Nicotine treatment reduced food intake by up to 40% in lean and obese P. obesus. Plasma leptin levels fell significantly only in lean nicotine-treated animals, whereas no changes were observed in obese nicotine-treated animals. However, both lean and obese nicotine-treated animals had similar reductions in body weight. Our results show that nicotine has dramatic effects on food intake and body weight, however, these changes appear to be independent of the leptin signalling pathway.

Weight management and weight loss strategies of professional jockeys

Jockeys are required to maintain very low body weight and precise weight control during competition. This study examined the weight loss and weight management strategies of professional horseracing jockeys in the state of Victoria, Australia. An anonymous, self-completed questionnaire was administered (55 % response rate, n = 116). Almost half (43 %) reported that maintaining riding weight was difficult or very difficult, with 75 % routinely skipping meals. In preparation for racing, 60 % reported that they typically required additional weight loss, with 81 % restricting food intake in the 24 hours prior to racing. Additionally, sauna-induced sweating (29 %) and diuretics (22 %) were frequently employed to further aid in weight loss prior to racing. These rapid weight loss methods did not differ between the 51 % of jockeys who followed a weight management plan compared to those who did not. The impact of these extreme weight loss practices on riding performance and health remains unknown.

Patterns and demographic predictors of 5-year weight change in a multi-ethnic cohort of men and women in Australia

Objective: This study investigated 5-year trends in body weight, overweight and obesity and their association with sociodemographic variables in a large, multi-ethnic community sample of Australian adults.  Design: This prospective population study used baseline and 5-year follow-up data from participants in the Melbourne Collaborative Cohort Study (MCCS). Setting: Population study in Melbourne, Australia. Subjects: In total, 12 125 men and 17 674 women aged 35–69 years at baseline. Results: Mean 5-year weight change in this sample was +1.58 (standard deviation (SD) 4.82) kg for men and +2.42 (SD 5.17) kg for women. Younger (35–44 years) men and, in particular, women gained more weight than older adults and were at highest risk of major weight gain ($5 kg) and becoming overweight. Risk of major weight gain and associations between demographic variables and weight change did not vary greatly by ethnicity. Education level showed complex associations with weight outcomes that differed by sex and ethnicity. Multivariate analyses showed that, among men, higher initial body weight was associated with decreased likelihood of major weight gain, whereas among women, those initially overweight or obese were about 20% more likely to experience major weight gain than underweight or healthy weight women. Conclusions: Findings of widespread weight gain across this entire population sample, and particularly among younger women and women who were already overweight, are a cause for alarm. The prevention of weight gain and obesity across the entire population should be an urgent public health priority. Young-to-mid adulthood appears to be a critical time to intervene to prevent future weight gain.

Measuring health in a vacuum: examining the disability weight of the DALY

The Disability Adjusted Life Year (DALY) is a widely used summary measure of population health combining years of life lost due to mortality and years of healthy life lost due to disability. A feature of the DALY is that, in the assessment of morbidity, each health condition is associated with a disability weight. The disability weight lies on a scale between 0 (indicating the health condition is equivalent to full health) and 1 (indicating the health condition is equivalent to death). The disability weight associated with each health condition is currently fixed across all social, cultural and environmental contexts. Thus blindness in the United Kingdom has the same disability weight as blindness in Niger in spite of structural interventions in the UK that make the disability less severe than in Niger. Although the fixed disability weight is defended on grounds that it supports a strongly egalitarian flavour in the DALY, we argue that the lack of consideration of realistic contexts results in a measure that will underestimate the burden associated with morbidity in disadvantaged populations and overestimate the burden in advantaged populations. There is, consequently, a loss of information on possible non-clinical points of intervention. Disaggregated estimates of the burden of disease such as those in the World Health Report 2000 should be interpreted with caution.