Benefits of a year-long workplace weight loss program on cardiovascular risk factors

Objective: To assess the effectiveness of a year-long workplace weight loss program in reducing risk factors of coronary heart disease.

Design: A randomised, controlled study of low fat (25% of dietary energy) diet- and/or moderate exercise-induced weight loss interventions in free-living, middle-aged men. Compliance was monitored from food and activity diaries at monthly blood pressure measurement sessions. Blood was sampled and body composition determined from dual energy X-ray absorptiometry before and after 12 months.

Subjects and setting: Fifty-eight overweight men (mean [+ or -] SD age: 43.4 [+ or -] 5.7 years; BMI 29.0 [+ or -] 2.6 kg/[m.sup.2]), recruited from a national corporation, were instructed into diet (n = 18) exercise (a 21) or control (n = 19) groups over 12 months; 16 control subjects combined diet and exercise (n = 16) for the subsequent 12 months.

Main outcome measures: At 12 months, weight, total and regional fat and lean mass, dietary energy and percentage dietary fat intake, physical activity indices, systolic and diastolic blood pressure, serum insulin, blood lipids and lipoproteins.

Statistical analyses: Differences between groups were tested using analysis of variance with Scheffe post hoc test. Differences between pre- and post-intervention variables were tested using Students' paired t-tests. Pearson's correlation coefficient and univariate linear regression identified association between dependent variables, multiple stepwise regression identified specific predictors.

Results: Weight loss with either diet or exercise resulted in a reduction in systolic blood pressure (-3.3 [+ or -] 1.7%), diastolic blood pressure (-4.8 [+ or -] 1.3%) and LDL cholesterol (-3.9 [+ or -] 2.8%), a rise in HDL cholesterol (+10.0 [+ or -] 3.8%) and a change in the LDL/HDL ratio (-8.9 [+ or -] 3.5%). Abdominal fat loss (-26.8 [+ or -] 3.6% after diet; -16.6 [+ or -] 4.5% after exercise; -21.0 [+ or -] 4.7% after diet and exercise) was the strongest predictor of change in blood pressure: twenty percent abdominal fat loss predicted a percentage fall of 2.4 [+ or -] 0.05% in systolic blood pressure and 5.4 [+ or -] 0.07% in diastolic blood pressure. Greater abdominal fat loss was associated with the greatest decrease in serum insulin (P < 0.05).

Conclusion: Modest changes in diet and exercise effected by a low cost workplace-based education program achieved weight loss, loss of abdominal fat, reduced blood pressure and serum insulin and improved blood lipid concentrations. (Nutr Diet 2002;59:87-96)

Quantifying the relationship between mechanical loading and the skeletal response in pre- and early-pubertal girls

PURPOSE
Before exercise prescription for bone health can be recommended, the relationship between mechanical loading characteristics and the skeletal response need to be quantified. We asked i) does moderate impact exercise result in a greater gain in BMC than low impact exercise, ii) what are the loading characteristics associated with a moderate and low impact exercise program and does this differ from non-structured play?, and iii) does loading history affect the osteogenic response to a moderate or low impact program?

METHODS
Sixty-eight pre- and early-pubertal girls (aged 8.9 +/- 0.2 yrs) were randomized to take part in a moderate or low impact exercise program 3 times/wk for 8.5 mnths. The number and type of loads associated with the exercise classes and non-structured play (recess) were assessed from video footage. The magnitude of load was assessed using a pedar in-sole mobile system. Hours of moderate and high impact organized sport were assessed from a physical activity questionnaire.

RESULTS
The moderate and low impact exercise programs consisted of -400 impacts per class, but the jumping, hopping and dynamic activities performed during the moderate impact program produced forces ranging from 2 to 4 times body weight (BW) compared to -1 BW for the low impact program. Moderate impact exercise resulted in a 2.7% greater gain in BMC at the tibia compared to the low impact exercise. The moderate impact exercise program consisted of fewer low impacts (1-2 BW) and a higher number of moderate impacts (2-4BW) compared to those typically performed during non-structured play. There were greater gains in BMC in subjects participating in the moderate versus the low impact exercise programs who participated in 2 to 3 hours of moderate impact sports outside school (2.5% to 4.5%, p

CONCLUSION
Approximately 400 impacts ranging 2-4 BW, 3 times/wk was enough stimuli to result in an osteogenic response in normally active girls; even in those actively involved in moderate impact sports outside school.

Estimating the changes in energy flux that characterize the rise in obesity prevalence

Background: The daily energy imbalance gap associated with the current population weight gain in the obesity epidemic is relatively small. However, the substantially higher body weights of populations that have accumulated over several years are associated with a substantially higher total energy expenditure (TEE) and total energy intake (TEI), or energy flux (EnFlux = TEE = TEI).
Objective: The objective was to develop an equation relating EnFlux to body weight in adults for estimating the rise in EnFlux associated with the obesity epidemic.
Design: Multicenter, cross-sectional data for TEE from doubly labeled water studies in 1399 adults aged 5.9 ± 18.8 y (mean ± SD) were analyzed in linear regression models with natural log (ln) weight as the dependent variable and ln EnFlux as the independent variable, adjusted for height, age, and sex. These equations were compared with those for children and applied to population trends in weight gain.
Results: ln EnFlux was positively related to ln weight (β = 0.71; 95% CI: 0.66, 0.76; R2 = 0.52), adjusted for height, age, and sex. This slope was significantly steeper than that previously described for children (β = 0.45; 95% CI: 0.38, 0.51).
Conclusions: This relation suggests that substantial increases in TEI have driven the increases in body weight over the past 3 decades. Adults have a higher proportional weight gain than children for the same proportional increase in energy intake, mostly because of a higher fat content of the weight being gained. The obesity epidemic will not be reversed without large reductions in energy intake, increases in physical activity, or both.

Cost-effectiveness of a family-based GP-mediated intervention targeting overweight and moderately obese children

Objective
 To assess from a societal perspective the incremental cost-effectiveness of a family-based GP-mediated intervention targeting overweight and moderately obese children. The intervention was modelled on the LEAP (live, eat and play) trial, a randomised controlled trial conducted by the Centre for Community Child Health, Melbourne, Australia in 2002–2003. This study was undertaken as part of the assessing cost-effectiveness (ACE) in obesity project which evaluated, using consistent methods, 13 interventions targeting unhealthy weight gain in children and adolescents.
Method
A logic pathway was used to model the effects of the intervention compared to no intervention on body mass index (BMI) and health outcomes (disability-adjusted life years—DALYs). Disease costs and health benefits were tracked until the cohort of eligible children reached the age of 100 years or death. Simulation-modelling techniques were used to present a 95% uncertainty interval around the cost-effectiveness ratio. The intervention was also assessed against a series of filters (‘equity’, ‘strength of evidence’, ‘acceptability’, ‘feasibility’, sustainability’ and ‘side-effects’) to incorporate additional factors that impact on resource allocation decisions.
Results
The intervention, as modelled, reached 9685 children aged 5–9 years with a BMI z-score of ≥3.0, and cost $AUD6.3M (or $AUD4.8M excluding time costs). It resulted in an incremental saving of 2300 BMI units which translated to 511 DALYs. The cost-offsets stemming from the intervention totalled $AUD3.6M, resulting in a net cost per DALY saved of $AUD4670 (dominated; $0.1M) (dominated means intervention costs more for less effect).
Conclusion
Compared to a ‘no intervention’ control group, the intervention was cost-effective under current assumptions, although the uncertainty intervals were wide. A key question related to the long-term sustainability of the small incremental weight loss reported, based on the 9-month follow-up results for LEAP.

Effects of tv time and other sedentary pursuits

Television (TV) viewing is the dominant recreational pastime at all ages, especially for children and adolescents. Many studies have shown that higher TV viewing hours are associated with higher body mass index (BMI), lower levels of fitness and higher blood cholesterol levels. Although the effect size estimated from observational studies is small (with TV viewing explaining very little of the variance in BMI), the results of intervention studies show large effect sizes. The potential mediators of the effect of higher TV viewing on higher BMI include less time for physical activity, reduced resting metabolic rate (for which there is little supporting evidence) and increased energy intake (from more eating while watching TV and a greater exposure to marketing of energy dense foods). Electronic games may have an effect on unhealthy weight gain, but are less related to increased energy intake and their usage is relatively new, making effect size difficult to determine. Thus, TV viewing does not explain much of the differences in body size between individuals or the rise in obesity over time, perhaps because of the uniformly high, but relatively stable, TV viewing hours. Reducing TV viewing hours is a difficult prospect because potential actions, such as social marketing and education, are likely to be relatively weak interventions, although the evidence would suggest that, if viewing could be reduced, it could have a significant impact on reducing obesity prevalence. Regulations to reduce the heavy marketing of energy dense foods and beverages on TV may be the most effective public health measure available to minimize the impact of TV viewing on unhealthy weight gain.

Weight status and perception barriers to healthy physical activity and diet behavior

Background : Physical inactivity and insufficient fruit and vegetable consumption are key risk factors for obesity and noncommunicable diseases. Weight perceptions may affect physical activity and diet behaviors. We report current prevalence estimates of Australian adults meeting recommended levels of leisure-time physical activity (LTPA) (150 min/week or more of at least moderate-intensity physical activity (including walking) on 5 days/week) and fruit (2 servings/day) and vegetable (5 servings/day) consumption for health benefits, by weight status and perceptions.
Methods : We conducted a cross-sectional survey analysis of data for 16 314 adults from the Australian National Health Survey 2004–2005. All variables were collected by self-report. Weighted estimates were age- and gender-specific, and data were analyzed using logistic regression with acceptable weight referent categories, adjusting for covariates.
Results : Among acceptable, overweight and obese adults, the prevalence of LTPA was 26.8, 26.1 and 19.3% for men, and 27.7, 23.7 and 19.7% for women, respectively. Approximately 55 and 15% of adults consumed sufficient fruit servings/day and vegetable servings/day, respectively, and less than 5% of adults met combined LTPA and diet guidelines. Overweight decreased the odds ratio for LTPA among women but not men, and obesity decreased the odds ratio for LTPA among both men and women. Overweight perception conferred odds ratios of 0.83 (95% CI 0.70–0.97, P=0.021) for overweight men, and of 0.74 (95% CI 0.62–0.88, P=0.001) and 0.69 (95% CI 0.59–0.80, P<0.001) for obese men and women, respectively; for LTPA, whereas no significant associations were found for acceptable weight perception. No consistent associations between weight status or perceptions and diet behaviors were found.
Conclusions : Overweight perception may be another barrier to physical activity participation among men and women with excess body weight. Public health strategies might need to focus on overcoming weight perception as well as weight status barriers to adopting healthy physical activity behaviors.

Cost-effectiveness of active transport for primary school children - Walking School Bus Program

Background : To assess from a societal perspective the incremental cost-effectiveness of the Walking School Bus (WSB) program for Australian primary school children as an obesity prevention measure. The intervention was modelled as part of the ACE-Obesity study, which evaluated, using consistent methods, thirteen interventions targeting unhealthy weight gain in Australian children and adolescents.

Methods : A logic pathway was used to model the effects on body mass index [BMI] and disability-adjusted life years [DALYs] of the Victorian WSB program if applied throughout Australia. Cost offsets and DALY benefits were modelled until the eligible cohort reached 100 years of age or death. The reference year was 2001. Second stage filter criteria ('equity', 'strength of evidence', 'acceptability', feasibility', sustainability' and 'side-effects') were assessed to incorporate additional factors that impact on resource allocation decisions.

Results : The modelled intervention reached 7,840 children aged 5 to 7 years and cost $AUD22.8M ($16.6M;$30.9M). This resulted in an incremental saving of 30 DALYs (7:104) and a net cost per DALY saved of $AUD0.76M ($0.23M; $3.32M). The evidence base was judged as 'weak' as there are no data available documenting the increase in the number of children walking due to the intervention. The high costs of the current approach may limit sustainability.

Conclusions : Under current modelling assumptions, the WSB program is not an effective or cost-effective measure to reduce childhood obesity. The attribution of some costs to non-obesity objectives (reduced traffic congestion and air pollution etc.) is justified to emphasise the other possible benefits. The program's cost-effectiveness would be improved by more comprehensive implementation within current infrastructure arrangements. The importance of active transport to school suggests that improvements in WSB or its variants need to be developed and fully evaluated.

Challenges of negotiating obesity-related findings with African migrants in Australia : lessons learnt from the African migrant capacity building and performance appraisal project

Aim: To document sub-Saharan African migrants' and teachers' reaction to and acceptance of findings from African Migrant Capacity Building and Performance Appraisal initiative, and to examine the implications for any community-based obesity prevention program.

Methods: Two community forums were organised to discuss the research findings: one with 45 African community leaders from various African communities in Melbourne; and the other with 17 primary and secondary teachers from English Language Schools and Centres across Victoria. The dissemination focused on highlighting the rapid weight gain and obesity risks observed among African migrant children.

Results: Sub-Saharan African migrants' reaction to the findings was that of pride and satisfaction with large body size, seeing it as a job well done, reflecting their perceptions that obesity is not a disease. In addition, they highlighted the intergenerational conflict related to body size ideals between parents and teenage offspring, with the latter preferring model-like Australian body sizes.

Conclusion: Further research is required to examine the association between shifting preferences in body ideals and obesity among traditional communities, such as sub-Saharan African migrants. The understanding of how changes in body image perceptions may influence eating and exercise behaviours among sub-Saharan African migrants would assist in the development of obesity-related preventive interventional programs for this at-risk population.

Effectiveness of prevention programmes for obesity and chronic diseases amongst immigrants to developed countries - a systematic review

Objective: To determine whether interventions tailored specifically to  particular immigrant groups from developing to developed countries  decrease the risk of obesity and obesity-related diseases.

Design: Databases searched were MEDLINE (1966–September 2008), CINAHL (1982–September 2008) and PsychINFO (1960–September 2008), as well as Sociological Abstracts, PsychARTICLES, Science Direct, Web of Knowledge and Google Scholar. Studies were included if they were randomised control trials, ‘quasi-randomised’ trials or controlled before-and-after studies. Due to the heterogeneity of study characteristics only a narrative synthesis was undertaken, describing the target population, type and reported impact of the intervention and the effect size.

Results: Thirteen studies met the inclusion criteria. Ten out of thirteen (77 %) studies focused on diabetes, seven (70 %) of which showed significant improvement in addressing diabetes-related behaviours and glycaemic control. The effect on diabetes was greater in culturally tailored and facilitated interventions that encompassed multiple strategies. Six out of the thirteen studies (46 %) incorporated anthropometric data, physical activity and healthy eating as ways to minimise weight gain and diabetes-related outcomes. Of the six interventions that included anthropometric data, only two (33 %) reported improvement in BMI Z-scores, total skinfold thickness or proportion of body fat. Only one in three (33 %) of the studies that included cardiovascular risk factors reported improvement in diastolic blood pressure after adjusting for baseline characteristics. All studies, except four, were of poor quality (small sample size, poor internal consistency of scale, not controlling for baseline characteristics).

Conclusions: Due to the small number of studies included in the present review, the findings that culturally tailored and facilitated interventions produce better outcomes than generalised interventions, and that intervention content is more important than the duration or venue, require further investigation.

Weight, physical activity and dietary behavior change in young mothers : short term results of the HeLP-her cluster randomized controlled trial

Background
Preventing weight gain rather than treating established obesity is an important economic and public health response to the rapidly increasing rates of obesity worldwide. Treatment of established obesity is complex and costly requiring multiple resources. Preventing weight gain potentially requires fewer resources to reach broad population groups, yet there is little evidence for successful interventions to prevent weight gain in the community. Women with children are an important target group because of high rates of weight gain and the potential to influence the health behaviors in family members.

Methods
The aim of this cluster randomized controlled trial was to evaluate the short term effect of a community-based self-management intervention to prevent weight gain. Two hundred and fifty mothers of young children (mean age 40 years ± 4.5, BMI 27.9 kg/m2 ± 5.6) were recruited from the community in Melbourne, Australia. The intervention group (n = 127) attended four interactive group sessions over 4 months, held in 12 local primary schools in 2006, and was compared to a group (n = 123) receiving a single, non-interactive, health education session. Data collection included self-reported weight (both groups), measured weight (intervention only), self-efficacy, dietary intake and physical activity.

Results
Mean measured weight decreased significantly in the intervention group (-0.78 kg 95% CI; -1.22 to -0.34, p < 0.001). Comparing groups using self-reported weight, both the intervention and comparison groups decreased weight, -0.75 kg (95% CI; -1.57 to 0.07, p = 0.07) and -0.72 kg (95% CI; -1.59 to 0.14 p = 0.10) respectively with no significant difference between groups (-0.03 kg, 95% CI; -1.32 to 1.26, p = 0.95). More women lost or maintained weight in the intervention group. The intervention group tended to have the greatest effect in those who were overweight at baseline and in those who weighed themselves regularly. Intervention women who rarely self-weighed gained weight (+0.07 kg) and regular self-weighers lost weight (-1.66 kg) a difference of -1.73 kg (95% CI; -3.35 to -0.11 p = 0.04). The intervention reported increased physical activity although the difference between groups did not reach significance. Both groups reported replacing high fat foods with low fat alternatives and self-efficacy deteriorated in the comparison group only.

Conclusion
Both a single health education session and interactive behavioral intervention will result in a similar weight loss in the short term, although more participants in the interactive intervention lost or maintained weight. There were small non-significant changes to physical activity and changes to fat intake specifically replacing high fat foods with low fat alternatives such as fruit and vegetables. Self-monitoring appears to enhance weight loss when part of an intervention.

Increased food energy supply is more than sufficient to explain the US epidemic of obesity

Background: The major drivers of the obesity epidemic are much debated and have considerable policy importance for the population-wide prevention of obesity.

Objective: The objective was to determine the relative contributions of increased energy intake and reduced physical activity to the US obesity epidemic.

Design: We predicted the changes in weight from the changes in estimated energy intakes in US children and adults between the 1970s and 2000s. The increased US food energy supply (adjusted for wastage and assumed to be proportional to energy intake) was apportioned to children and adults and inserted into equations that relate energy intake to body weight derived from doubly labeled water studies. The weight increases predicted from the equations were compared with weight increases measured in representative US surveys over the same period.

Results: For children, the measured weight gain was 4.0 kg, and the predicted weight gain for the increased energy intake was identical at 4.0 kg. For adults, the measured weight gain was 8.6 kg, whereas the predicted weight gain was somewhat higher (10.8 kg).

Conclusions: Increased energy intake appears to be more than sufficient to explain weight gain in the US population. A reversal of the increase in energy intake of 2000 kJ/d (500 kcal/d) for adults and of 1500 kJ/d (350 kcal/d) for children would be needed for a reversal to the mean body weights of the 1970s. Alternatively, large compensatory increases in physical activity (eg, 110–150 min of walking/d), or a combination of both, would achieve the same outcome. Population approaches to reducing obesity should emphasize a reduction in the drivers of increased energy intake.

Parents' perceptions and concerns about their children's weight

Background: For parents to address overweight or obesity in their children, they first need to perceive their child to be overweight and to show some level of concern. We aimed to: (1) measure the level of misclassification between children’s actual and parent-perceived weight status, and (2) determine the level of parent concern about their child’s (actual) weight and whether concern varied according to the accuracy of parents’ perceptions.

Methods: Participants were 1711 primary school children aged 5–12 years from the Barwon-South West region of Victoria, Australia. Height and weight were measured and weight status determined using international standards. Parents completed a Computer Assisted Telephone Interview (CATI) that included questions relating to their child’s weight.

Results: 448 children (26.2% of sample) were overweight or obese. Of these, weight status for almost half (48%) was underestimated by parents. This ‘bias’ did not vary according to the child’s gender, parent’s education, or household socio-economic status but did for child’s age and parent-respondent gender. More than half (57%) of the parents of overweight-obese children expressed no concern about their child’s weight. Parents who underestimated the weight status of their overweight child were significantly less concerned (P < 0.001) about their child’s weight than those who correctly perceived their child as overweight.

Conclusions: Parents were relatively poor judges of overweight or obesity in their own child and consequently there was a lack of appropriately directed concern. Education to help parents correctly classify their child’s weight status should be part of efforts to prevent unhealthy weight gain.

Lesbians' experience of menopause

This thesis examines the menopausal experiences of a non-clinical sample of lesbians living in Australia. Research on menopause to date has largely been conducted from a medicalised and heterosexual perspective: thus lesbians’ experiences remain unknown and invisible. Using a qualitative feminist multiple method research methodology combining content analysis and questionnaire/interview research, two hundred questionnaires were posted upon request to self-identified lesbians living in every Australian state and territory. Follow up in-depth interviews were conducted with twenty lesbians. Responses were grouped into four major themes: body image, sex and sexuality, hormone replacement therapy and health services and homophobia. The findings show that lesbians at menopause face some different and additional issues from those experienced by heterosexual midlife women. For many of the study participants, commonly discussed concerns at menopause such as weight gain and other physical signs of ageing, decreased fertility, lack of libido, sexual difficulties and hormone replacement therapy were of little relevance and importance. Lesbians in this study frequently raised other issues such as the universal assumption of heterosexuality and homophobia experienced when interacting with health professionals, which led to less than satisfactory health care and reinforced feelings of invisibility. In the Conclusion I argue that the study participants' views and experiences challenge negative, stereotypical views of both lesbians and menopause. The data thus add a new dimension to the presently narrow, heterosexist and medicalised view of women at midlife and contribute new knowledge to the body of literature on menopause. This thesis is a first important step in recording the experiences of lesbians regarding menopause in Australia. I include recommendations for further research in the area of lesbian health and improved practice, and discuss old and new obstacles lesbians face in a heteropatriarchal society in which lesbians continue to be invisible.

Nutrition, growth and production of Cherax Destructor Clark, 1936 (Decapoda, Parastacidae)

In this study the nutrition, growth and production of C. destructor was examined. Selected nutritional requirements of juvenile animals were determined under controlled conditions with the aim of developing a pelleted diet for use in hatcheries, nurseries and growout situations. The best developed diet was assessed for its potential as a supplementary feed for animals cultured in earthen environments. The protein requirements were first determined simultaneously with an evaluation of the effect of replacing animal protein (fishmeal) by soybean meal. Juveniles were reared communally for 59 d on isoenergetic diets containing 15-30% protein and graded levels of soybean meal (0-60%, of protein). When soybean meal was included at a level of 40-60%, growth was reduced relative to that achieved with control diets containing 15% and 20% protein, but this was not the case at a 20% soybean meal substitution level. A two-way interaction occurred between dietary protein and soybean meal content. Higher protein feeds enabled higher soybean meal inclusion levels without significantly affecting growth. Protein increases of 5% produced better growth at the 40% and 60% soybean meal substitution levels. This effect was less pronounced in the control and the 20% soybean meal diets. Carcass %protein increased and %lipid decreased as dietary protein increased. A similar effect occurred by increasing the soybean meal level to 60%. No obvious trend in carcass moisture, energy, and ash occurred. A protein requirement of 30% was apparent when fish meal and soybean meal were included in diets at levels of 20% and 24% (dry matter) respectively. Alternative protein sources to soybean meal were subsequently identified. Juveniles were maintained for 12 weeks on isoenergetic diets containing 30% protein and differing in the primary source of protein used, with meat, snail, soybean, yabby, and zooplankton meals comprising the major protein ingredient. No significant difference occurred in mean weight (MW), percentage weight gain (%WG), SGR or survival among diets. Food conversion ratios (FCR) were low, with a minimum value of 0.95 for the snail-based diet. The apparent net protein utilisation (ANPU) varied from 29.6% (zooplankton-based diet) to 41.2% (snail-based diet). Carcass composition varied with diet, with the greatest difference occurring in carapace colour. Animals fed the zooplankton-based diet developed the strongest, most natural pigmentation. A new combination of previously used protein-based ingredients was subsequently tested with reference to two yabby species, Cherax albidus and Cherax destructor, that were grown simultaneously in identical conditions. Juvenile male animals were reared individually for 20 weeks on isoenergetic diets containing 15% or 30% protein with fish meal, soybean meal, yabby meal and wheat products forming the basis of the diets. C albidus grew the fastest and utilised the food the most effectively. Carcass composition was influenced by diet with the 30% protein diet resulting in an increase in carcass protein and ash and a decrease in carcass lipid and energy relative to the low protein diet. Carcass moisture and calcium were not affected by diet. The intermoult period (IP) was highly dependent on the premoult weight (W) but the mean moult increment (WI, as weight) was independent of the PM. The orbital carapace length (OCL) and the abdominal length (ABL) %moult increments generally declined with an increase in PM whereas the propus length (PL) %moult increment generally increased. The IP, WI, %OCL, %ABL, and %PL moult increments varied according to diet and to species. Elevated dietary protein caused a reduction to the IP (for similar sized animals) by 11 d and 7 d and an increase to the WI by 85% and 81% in C. albidus and C destructor respectively. Dietary induced morphological changes also occurred. Animals of a standard OCL (both species) had significantly larger abdomens when fed the higher protein diet. Growth on the best developed diet was compared to the growth obtained on a natural diet of freshwater zooplankton. Juveniles were reared individually for 12 weeks on the two diets. The MW, %WG and SGR were higher for the zooplankton diet. Carcass composition was influenced by diet and the zooplankton fed animals had a higher carcass %protein, %lipid, %ash and %fibre content and were more richly pigmented than animals fed pellets. The IP and the WI were highly dependent on the PM and varied according to diet; feeding with zooplankton reduced the IP by 1.2 days and increased the WI by 13.7% compared to pellets. Nutrient digestibility was determined for the pelleted diets evaluated in the growth trials. Protein digestibility (PD) and dry matter digestibility (DMD), using chromic oxide (Cr2O3) as an exogenous marker, were high for all diets, at around 93% and 83% respectively. Ash digestibility varied considerably from 17% to 73% for the snail and yabby meal diets respectively. Crude fibre digestibility was around 50% and probably indicates cellulase activity. Alternative markers to Cr2O3 were evaluated. Ash was considered to be the most suitable alternative to Cr2O3, providing a reasonable, albeit lower, estimate of nutrient digestibility. Cr2O3 and ash were preferentially excreted whereas fibre was retained in the digestive system for a longer period, consequently, the collection of a particular fraction of the deposited faeces (late or early) substantially affected the digestibility coefficients. In earthen-based environments, animals fed the best developed diet were compared to animals cultured using a forage crop of clover (Trifolium repens). Three supplementary feeding strategies representing varying levels of management intensity were evaluated in a series of trials conducted in ponds and pond microcosms. Growth on pellets consistently exceeded that obtained with the forage crop, with final MW being 67-159% higher than that using clover and appeared to be the result of direct pellet consumption and from a pellet fertiliser effect (on the sediment). Within-pond DMD and PD were high and similar for each treatment (DMD = 51-58%; PD = 89-92%). In the control pond, DMD and PD increased with each successive flood. The faecal egestion rate (PER) decreased with each successive flood in all ponds, and is negatively related to animal weight and to foregut fullness (FF) according to power curves. FF was consistently lowest in the control pond. Mean FF was 48.5%, 62.3%, and 26.7% for the pellet, crop and control ponds respectively. FF increased to the third flood in each pond. The foregut protein content was high in all samples and the mean values were 33.9%, 32.7% and 35.6% for the pellet, crop and control ponds respectively. Foregut ash was highly variable within each pond and is inversely related to the foregut protein content. In the control and pellet ponds the highest foregut ash content occurred during flood 1. The culture system (aquaria or pond) strongly influenced the composition of the foregut content. The foregut of animals fed the manufactured diet (B2) in ponds contained approximately 176% more ash and 5% more protein than the foregut of animals fed in bare-bottom tanks. The FF of the tank fed animals was approximately 45% higher than the FF of pond fed animals after a similar feeding period. Base-line yields for extensive production systems appeared to be around 400kg ha-1. The supplementary addition of T. repens produced yields of approximately 635kg ha-1 (in ponds) to around 1086kg ha-1 (in tanks). The sequential addition of cut-clover to tanks stimulated growth to levels approaching those achieved on pellets. Yabbies stocked into ponds at 15-20 m-2 with a mean weight of 2.67g and fed a 30% protein pelleted diet for 100 d, resulted in a yield of approximately 1117kg ha-1, but only 2% of the population were above a marketable size of 50g. The feed utilisation indices were better for animals reared on pellets in bare-bottom tanks than in earthen environments, indicating some degree of pellet wastage when natural feeds are simultaneously present. High apparent food conversion ratios and low protein efficiency ratios occurred when the forage crop was provided. A considerable quantity of the dry matter and protein content of the forage crop was either inefficiently utilised or directed into other production pathways. Sowing a forage crop into pond microcosms to which a pelleted diet was also provided, did not enhance growth performance. Pelleted feed inputs at a rate of approximately 129g m-2 to 198g m-2 (dry matter) and 38g -2 to 64g m-2 (protein) over 70-100 d resulted in acceptable growth and feed utilisation indices for animals reared in ponds and pond microcosms. Forage crop inputs of approximately 533g m-2 to 680g m-2 (as dry matter) or 84g m-2 to 177g m-2 (as protein) over a 70-100 d period produced reasonable growth rates but poor feed utilisation indices. Low inputs of dry matter (from 113-296g m-2) and protein (from 24-54g m-2) from clover were sufficient to maintain high growth rates in pond microcosms for around 28 d. In ponds, a very low level of 21g m-2 (dry matter) and 4.3g m-2 (protein) was sufficient for around 3 weeks. Forage depletion appeared to occur beyond week 3-4 and was probably a major growth limiting factor. The mean hepatosomatic index (HSI) was 9.44, 7.68, and 6.79 for the pellet, crop, and control ponds respectively. The relationship between hepatopancreas weight and overall animal weight was significantly different between treatments. The hepatopancreas of pellet-fed animals had the highest %lipid and lowest %ash, %protein, %carbohydrate and %moisture content. In terms of absolute quantities, the only major difference in hepatopancreas composition between treatments occurred for lipid and dry matter content. The hepatopancreas of the pellet-fed animals was a cream/cream-yellow colour and was very fragile, whereas in the other ponds it was a more ‘natural’ bright yellow colour and was structurally more robust. C. destructor has a capacious foregut, being approximately 5 times the volume of similar sized Penaeids. The foregut volume (V, ml) of the yabby is related to animal weight (W, g) according to V = 0.048 W0.9543. Animals that were starved for 96 h and then fed diet B2 were almost completely foil after 30 min. The ‘apparent enzymatic response’ of animals fed various natural and artificial diets in tanks was evaluated. Nutrient processing time and the enzymatic response following ingestion appeared to be regulated by the chemical and physical properties of the diet. For the natural feeds, foregut protein was 1.2% higher (for zooplankton) and up to 300% higher (for detritus) than dietary protein, whereas ash was 7.5% higher (zooplankton) and 46-63% lower (detritus) than dietary ash. For animals fed diet B2 after 48 h without food, FF was approximately half that of 96 h starved animals after a similar feeding period but foregut protein and ash contents were similar. Finally, the physiological and morphological attributes elucidated in this study are discussed with reference to the ecology of the yabby. High growth rates, excellent feed utilisation indices and high digestibility coefficients for a wide range of diet-types illustrate nutritional flexibility. A capacious foregut, a large hepatopancreas with a high energy storage capacity, the ability to partition and preferentially excrete the low nutrient value inorganic component of the diet, the capacity to alter body form, nutrient processing time and enzymatic secretions in relation to diet-type, and modified behaviour according to feed availability also demonstrate plasticity/adaptability/flexibility. The combined effect of these important characteristics ensures survival in environments that may be adverse and highly variable in terms of nutrient availability. Collectively the morphological and digestive traits elucidated in this study reflect the generalist-type nature of C destructor and indicate that a polytrophic classification still seems appropriate. Several priority areas for further nutrition research are identified and recommendations are made regarding the best-practices to use in the commercial culture of the yabby. Of paramount importance is the further clarification of the nutritional requirements and feeding preferences of animals in various phases of development.

Determination of human body composition

This thesis deals with two electrical methods designed to enable rapid, safe and noninvasive measurement of body composition, both for clinical and community use. The first section provides a review of the literature related to measurement of body composition in humans and outlines the approach of the research project. The second section deals with established methods of determining body composition, the two most important being hydrostatic densitometry and deuterium oxide dilution. In this part of the report, a novel method for measuring lung volume by hydrogen dilution at the time of underwater weighing is described. The main findings of the thesis are contained in the third section which deals with the assessment of body opposition by electrical means. There are two components to this part of the study. The first involved the testing of a commercially available bioelectric impedance analyser (BIA) which measures impedance to a flow of current through the body. Studies on the reproducibility and reliability of measurements were performed. Results showed the importance of correct electrode placement and revealed that subjects can consume a light meal and a drink before being measured with the BIA without adversely affecting impedance readings. Results suggested, however, that subjects empty their bladders before measurements are made. Strong correlations were found between height 2/ resistance and measurements of total body water (r = 0.839) and fat-free weight derived from densitometry (r = 0.821), Moderate correlations (r = 0.6 to 0.7) were also found when height /resistance was related to fat-free weight derived from anthropometric measurements. The second and major consonant of the third section deals with the development of a method based on the absorption of energy from a weak electromagnetic field established in a capacitor or chamber large enough to accommodate an adult human subject. The method involves measurement of the effect of the body on the electromagnetic field, and is based on differential absorption of energy by body fat and fat-free tissues. Regression equations were developed for predicting the weight of fat and fat-free tissue in the body from measurement of electromagnetic field effects in a test capacitor and in a resonating chamber. The test capacitor comprised a large aluminum cylinder with a copper rod as a central conductor. The following equation was derived for the relationship of fat-free weight (FEW) based on body density, with measurements of change in resonant frequency (ΔfR), height (H) and weight (W) : FFW = -4.39 + 0.690 W + 19.9 H + 37.6 ΔfR In a study of 17 subjects, a value of 0.891 was found for R2, and S.E.E. was 1.63. The resonating chamber consisted of a large enclosed aluminium cylinder with a copper rod as a central conductor. The following equation was derived for the relationship of fat weight (FW) based on the mean of estimates from body density and total body water, with measurements of change in signal attenuation (ΔA), change in resonant frequency (ΔfR), and height (H) and weight (W) : FW = 73.48 + 0.291 (W/√(ΔA) - 49.2 H - 0.53 ΔfR In a study of 27 subjects, a value of 0.956 was found for R2, and S.E.E. was 1.97. In these equations, variables were measured in the following units : FEW, FW and W (kg), ΔfR (MHz) and H (m).