None listed
Conditions
Brief summary
There are more than 7 million overweight or obese adults in Australia and on average only about 5% of this population achieve permanent weight reduction of any significance to their health. Many questions remain regarding the best way to achieve long-term weight loss, and how a person’s metabolic rate is affected both in the short- and long-term during dieting. The overall aim of this project is to design more effective and sustainable weight loss strategies for overweight and obese adults. This study, funded by the National Health and Medical Research Council (NHMRC), aims to compare changes in weight and health using two different dieting approaches; one in which the energy intake (kilojoule value) changes every two weeks, and the other where the energy intake changes every four weeks. Throughout the intensive phase of the study, participants are provided with a healthy, balanced, energy-regulated diet delivered to their home. Measures of body composition, metabolic rate and energy expenditure, hunger and satiety, blood hormone levels, body fuel usage, and metabolic health will be taken at a number of time points throughout the study.
Interventions
The study will comprise 3 phases: [1] Baseline energy balance, [2] Energy restriction intervention, and [3] Post-intervention energy balance. As we have previously shown that provision of food maximises dietary compliance in the free-living situation (1,2,4), food will be home-delivered weekly to participants in all phases of this study. The aim of PHASE 1 is to determine the baseline values of various parameters of the famine reaction before energy restriction and weight loss. During the 4 week
The study will comprise 3 phases: [1] Baseline energy balance, [2] Energy restriction intervention, and [3] Post-intervention energy balance. As we have previously shown that provision of food maximises dietary compliance in the free-living situation (1,2,4), food will be home-delivered weekly to participants in all phases of this study. The aim of PHASE 1 is to determine the baseline values of various parameters of the famine reaction before energy restriction and weight loss. During the 4 weeks of PHASE 1, weight stability will be achieved as we have previously published (1-4), by determining maintenance energy requirements from dietary history and resting metabolic rate (RMR), and then providing participants with a weight maintenance diet. In PHASE 2, participants will be randomised to continuous or intermittent energy restriction interventions. The continuous intervention consists of 16 weeks on a diet at 67% of maintenance energy requirements. The intermittent intervention consists of 16 weeks of total energy restriction administered as 2 weeks of energy restriction on a diet at 67% of maintenance energy requirements followed by 2 weeks of energy balance on a diet at 100% of maintenance energy requirements, for a total of 30 weeks. The interventions are designed to elicit a 10% body weight loss. To account for weight lost, the energy restriction will be indexed to body weight and RMR after every 4 weeks of energy restriction, thereby keeping theoretical relative energy deficit consistent across the 16-week period. In PHASE 3, participants will be placed on an energy balance diet referenced to their reduced-weight state for 4 weeks to examine the time course of recovery of metabolic and neuroendocrine markers. The macronutrient distribution in both energy restriction and energy balance diets will be maintained within the range of 25–30% of energy as fat, 15-20% as protein, and 50–60% as carbohydrate. As we have previously shown that provision of food maximises dietary compliance in the free-living situation (1,2,4), food will be home-delivered weekly to participants in this study. 1. Weinsier RL, Hunter GR, Desmond RA, Byrne NM, Zuckerman PA, Darnell BE. Free-living activity energy expenditure in women successful and unsuccessful at maintaining a normal body weight. Am J Clin Nutr. 2002; 75(3):499-504. 2. Byrne NM, Hills AP, Wood RE. Does body composition, relative energy deficit or adaptive thermogenesis explain differences between predicted and actual weight loss in obese adults? Obesity Reviews. 2010;11(Suppl.1):35-36. 3. Byrne NM, Weinsier RL, Hunter GR, et al. Influence of distribution of lean body mass on resting metabolic rate after weight loss and weight regain: comparison of responses in white and black women. Am J Clin Nutr. 2003;77(6):1368-73. 4. Wood RE, Byrne NM, Groves AM, Hills AP, King NK. Achieving energy balance in apparently sedentary obese males. Obesity Reviews. 2010;11(Suppl.1):219.
Sponsors
Professor Nuala Byrne
Study design
Allocation
Randomised controlled trial
Intervention model
Parallel
Primary purpose
Treatment
Masking
Open (masking not used)
Eligibility
Sex/Gender
Male
Age
25 Years to 53 Years
Healthy volunteers
No
Inclusion criteria
Sedentary (< 60 mins physical activity per week) Class I or II obese (30-40kg.m-2) Waist circumference >102 cm Euthyroid, non-diabetic, ambulatory, and weight stable for at least 6 months (+/-2kg)
Exclusion criteria
Diabetic or fasting blood glucose > 6.0 mmol/L (from medical screening) Major surgery that will affect gut function/metabolic rate Arthritis/musculoskeletal problems that would preclude full participation in all testing/affect activities of daily living Heart condition Sleep apnoea Thyroid condition Current smoker or gave up smoking within the last 6 months Any medications known to affect metabolic rate or neuroendocrine function Non-ambulatory Currently on a “diet” or actively losing weight
Outcome results
None listed