Studies on the Variability of Human Basal Metabolic Rate

The studies presented in this thesis examine some of the factors responsible for variation in basal metabolic rate (BMR, defined as the energy expended by an individual lying quietly at rest in a thermoneutral environment, at least 12 hours postabsorptive). They are particularly concerned with the parts played by differences in body composition and cellular metabolic activity, under the influence of thyroid hormones and catechloamines, in explaining variability in BMR. In the great majority of people, and certainly most of those living in an industrialised society, BMR accounts for the largest part of daily energy expenditure, often making up more than two thirds of the total. Study of the factors that effect BMR is therefore central to our understanding of the causes of variation in daily energy needs. The first study undertaken sought to explore some of the general relationships between BMR and body composition in a group of 97 healthy women. BMR was measured using the Douglas bag technique, and body composition assessed by measurements of weight, height, body fat content (skinfold and densitometry estimates), circumferences and diameters. Differences in BMR between the women were found to be large (CV = 11.8%, standard deviation 159 kcal/day) and could be best explained by differences in FFM, accounting for 45 % of the total variance. The relationship between BMR and FFM was unaffected by body fatness or age. However, at a given FFM considerable variation in the BMR of individual women was evident. Moreover, for the purposes of predicting an individual's BMR, FFM was found to be no better than body weight. Simple differences in the weight of the FFM therefore, could only partially explain the variation in BMR between the women. A further observation from the study was that BMR expressed per kg body weight or per kg FFM tended to decline form light to heavy individuals. This finding has implications for the use of FFM as a metabolic reference standard, and it is suggested that it may relate to differences in the composition of the FFM. The role of the catecholamines was considered in a study which investigated the effect of B-adrenergic blockade on basal metabolic rate. The BMRs (measured using a ventilated hood system) of a group of 18 patients receiving beta blocker drugs in the treatment of cardiovascular disorders were compared to those of 28 healthy control subjects. In relation to the FFM (estimated from skinfold thicknesses) the BMRs of the B-blocker patients were found to 8% lower than that of the controls, equivalent to 136 kcal/day. The study revealed a potentially important side effect of this widely prescribed group of drugs and moreover, suggested that BMR has an adrenergically mediated component. A further study was undertaken with the aim of elucidating the causes of the marked variation in BMR relative to the FFM observed in the initial investigation. Two groups of women characterised by particularly high or low BMRs in relation to their FFM were selected for further study. Repeat measurements of BMR suggested that part of the differences between the groups, and by extension the initial study also, resulted from within-subject variation in BMR. Error in measurement of the FFM (estimated by skinfolds, total body water and densitometry) was found to be small and its potential contribution considered minor. It was estimated that genuine inter-individual variation in BMR in relation to the FFM was in the region of 100 kcal/day. Thyroid hormone levels were found to be significantly greater in the high BMR group than in the low and it was postulated that these differences were likely to be responsible for at least part of the variance in BMR relative to FFM. Thyroid status did not however, provide the complete explanation, a residual standard deviation approximately 70 kcal/day remained. It was considered likely that differences in the composition of the FFM were involved in explaining the remaining variance. Urinary catecholamine levels were comparable in both groups, however the possibility that differences in an adrenergically mediated process may have contributed to the differences in BMR could not be ruled out. Traditionally, differences in BMR have been ascribed to differences in body size, age, sex, race, climate and nutritional status. The studies presented in this thesis suggest however, that that these may have a common basis in that they relate to differences in one or both of the major determinants of BMR; to differences in body composition - primarily to the mass of fat-free tissue and to the relative proportions of its component parts - and to hormonally induced metabolic activity of the tissues

Development and Evaluation of a Computer-Based, Self-Management Tool for People Recently Diagnosed with Type 2 Diabetes

Aim. The purpose of this study was to develop and evaluate a computer-based, dietary, and physical activity self-management program for people recently diagnosed with type 2 diabetes. Methods. The computer-based program was developed in conjunction with the target group and evaluated in a 12-week randomised controlled trial (RCT). Participants were randomised to the intervention (computer-program) or control group (usual care). Primary outcomes were diabetes knowledge and goal setting (ADKnowl questionnaire, Diabetes Obstacles Questionnaire (DOQ)) measured at baseline and week 12. User feedback on the program was obtained via a questionnaire and focus groups. Results. Seventy participants completed the 12-week RCT (32 intervention, 38 control, mean age 59 (SD) years). After completion there was a significant between-group difference in the "knowledge and beliefs scale" of the DOQ. Two-thirds of the intervention group rated the program as either good or very good, 92% would recommend the program to others, and 96% agreed that the information within the program was clear and easy to understand. Conclusions. The computer-program resulted in a small but statistically significant improvement in diet-related knowledge and user satisfaction was high. With some further development, this computer-based educational tool may be a useful adjunct to diabetes self-management. This trial is registered with clinicaltrials.gov NCT number NCT00877851

The Effect of Processing and Seasonallity on the Iodine and Selenium Concentration of Cow's Milk Produced in Northern Ireland (NI): Implications for Population Dietary Intake

Cow’s milk is the most important dietary source of iodine in the UK and Ireland, and also contributes to dietary selenium intakes. The aim of this study was to investigate the effect of season, milk fat class (whole; semi-skimmed; skimmed) and pasteurisation on iodine and selenium concentrations in Northern Ireland (NI) milk, and to estimate the contribution of this milk to consumer iodine and selenium intakes. Milk samples (unpasteurised, whole, semi-skimmed and skimmed) were collected weekly from two large NI creameries between May 2013 and April 2014 and were analysed by inductively coupled plasma-mass spectrometry (ICP-MS). Using milk consumption data from the National Diet and Nutrition Survey (NDNS) Rolling Programme, the contribution of milk (at iodine and selenium concentrations measured in the present study) to UK dietary intakes was estimated. The mean ± standard deviation (SD) iodine concentration of milk was 475.9 ± 63.5 µg/kg and the mean selenium concentration of milk was 17.8 ± 2.7 µg/kg. Season had an important determining effect on the iodine, but not the selenium, content of cow’s milk, where iodine concentrations were highest in milk produced in spring compared to autumn months (534.3 ± 53.7 vs. 433.6 ± 57.8 µg/kg, respectively; p = 0.001). The measured iodine and selenium concentrations of NI milk were higher than those listed in current UK Food Composition Databases (Food Standards Agency (FSA) (2002); FSA (2015)). The dietary modelling analysis confirmed that milk makes an important contribution to iodine and selenium intakes. This contribution may be higher than previously estimated if iodine and selenium (+25.0 and +1.1 µg/day respectively) concentrations measured in the present study were replicable across the UK at the current level of milk consumption. Iodine intakes were theoretically shown to vary by season concurrent with the seasonal variation in NI milk iodine concentrations. Routine monitoring of milk iodine concentrations is required and efforts should be made to understand reasons for fluctuations in milk iodine concentrations, in order to realise the nutritional impact to consumers

Diet and physical activity in the self management of type 2 diabetes: barriers and facilitators identified by patients and health professionals

Aim:&nbsp;To explore the views of individuals recently diagnosed with type 2 diabetes in&nbsp;relation to self-management of dietary intake and physical activity, and to compare these&nbsp;with the views of health professionals (HPs). Background: Diabetes education has&nbsp;become a priority area in primary and secondary care, and many education programmes&nbsp;are now embedded within a patient&rsquo;s care package. There are few contemporaneous&nbsp;explorations of patients&rsquo; views about lifestyle self-management. Such research is vital in&nbsp;order to identify areas that require further support, refinement or enhancement in terms&nbsp;of patient education. Methods: Focus groups were held with patients recently diagnosed&nbsp;with type 2 diabetes (n516, 38% female, aged 45&ndash;73 years). In-depth semi-structured&nbsp;interviews were conducted with HPs (n57). Discussions focussed on self-management&nbsp;specifically in relation to making dietary and physical activity changes. All discussions&nbsp;were tape recorded, transcribed and analysed by emergent themes analysis using NVivo&nbsp;to manage the coded data. Findings: Barriers were divided into six main categories:&nbsp;difficulty changing well- stablished habits, negative perception of the &lsquo;new&rsquo; or recommended&nbsp;regimen, barriers relating to social circumstances, lack of knowledge and&nbsp;understanding, lack of motivation and barriers relating to the practicalities of making&nbsp;lifestyle changes. HPs generally echoed the views of patients. In conclusion, even against&nbsp;a background of diabetes education, recently diagnosed patients with type 2 diabetes discussed a wide range of barriers to self-management of diet and physical activity.&nbsp;The findings could help to provide HPs with a deeper understanding of the needs of&nbsp;recently diagnosed patients and may help refine current diabetes education activities and&nbsp;inform the development of educational resources.</div

Development and evaluation of a computer-based, self-management tool for people recently diagnosed with type 2 diabetes

Aim. The purpose of this study was to develop and evaluate a computer-based, dietary, and physical activity self-management program for people recently diagnosed with type 2 diabetes. Methods. The computer-based program was developed in conjunction with the target group and evaluated in a 12-week randomised controlled trial (RCT). Participants were randomised to the intervention (computer-program) or control group (usual care). Primary outcomes were diabetes knowledge and goal setting (ADKnowl questionnaire, Diabetes Obstacles Questionnaire (DOQ)) measured at baseline and week 12. User feedback on the program was obtained via a questionnaire and focus groups. Results. Seventy participants completed the 12-week RCT (32 intervention, 38 control, mean age 59 (SD) years). After completion there was a significant between-group difference in the &quot;knowledge and beliefs scale&quot; of the DOQ. Two-thirds of the intervention group rated the program as either good or very good, 92% would recommend the program to others, and 96% agreed that the information within the program was clear and easy to understand. Conclusions. The computer-program resulted in a small but statistically significant improvement in diet-related knowledge and user satisfaction was high. With some further development, this computer-based educational tool may be a useful adjunct to diabetes self-management. This trial is registered with clinicaltrials.gov NCT number NCT00877851