None listed
Conditions
Brief summary
Dietary restriction (dieting) is the most popular method for weight loss and is commonly the first strategy prescribed for weight loss in treating obesity. However, dietary interventions are often ineffective because energy restriction triggers the so-called “famine reaction”, a survival mechanism used by the body in order to conserve energy in times of starvation. The famine reaction involves a series of metabolic and behavioural adaptations including compensatory changes in metabolic rate, appetite and neuroendocrine hormones as well as a loss in metabolically active lean tissue in order to reduce energy requirements. Little is known about the underlying mechanisms involved in the famine reaction or whether different dietary restriction interventions can alter this response leading to more efficient and sustained weight loss. Our research group has found that a novel intermittent diet approach results in greater weight loss, reduced levels of stress hormone cortisol in blood and attenuation of the famine reaction. It is well known that dieting is psychologically stressful, and there are strong connections between stress and weight control through elevations of cortisol. Cortisol promotes central adiposity (obesity) and muscle loss and may lead to reductions in metabolic rate. Cortisol also stimulates appetite and cravings for sweet and fatty foods. For these reasons cortisol likely plays a major role in causing diet failure and resistance to weight loss. Therefore, one aspect of our study is to better understand the relationship between stress and weight loss. In order to investigate these, we firstly need to establish laboratory methods at Bond University and optimal conditions for measuring cortisol in lean healthy and obese humans. These studies will then enable us to apply these skills and perform larger weight loss interventions. The information gained for these studies will provide a greater understanding on the underlying mechanisms involved in the famine reaction and why individuals with obesity struggle to achieve weight loss goals; thereby, leading to new therapeutic strategies to target obesity.
Interventions
This study will investigate the relationship between weight and stress (cortisol metabolism). Specifically, in healthy and obese men and women we will firstly determine the optimum conditions for measuring cortisol, and compare and contrast differences between collection methods (ie. saliva, fasting blood and 24h urine). We will also obtain subcutaneous adipose tissue and skeletal muscle biopsies to study cortisol metabolism in target tissues, and link these with differences in resting metabolic
This study will investigate the relationship between weight and stress (cortisol metabolism). Specifically, in healthy and obese men and women we will firstly determine the optimum conditions for measuring cortisol, and compare and contrast differences between collection methods (ie. saliva, fasting blood and 24h urine). We will also obtain subcutaneous adipose tissue and skeletal muscle biopsies to study cortisol metabolism in target tissues, and link these with differences in resting metabolic rate, body composition, stress, anxiety and depression and sleep quality, physical activity levels and previous weight history. We will also assess reproducibility between samples taken from each participant. The duration of the study will be three weeks. We will collect samples/ take each measurement up to three times during this period.
Sponsors
Bond University
Eligibility
Sex/Gender
All
Age
18 Years to 60 Years
Healthy volunteers
Yes
Inclusion criteria
Participants may be included in the study if they are an adult (over the age of 18) and are Sedentary (< 60 min of physical activity per week), either class I or II obese (30-40 +/- 2 kg.m-2) and have a waist circumference >88 cm if female or >102cm if male or lean healthy (18.5-24.9 kg.m-2 and have a waist circumference <88 cm if female or <102cm if male; weight stable (i.e. have not gained or lost more than 2 kg in the previous 6 months), of Caucasian ancestry and with no medical conditions or medications that will impact on their hormonal profile, cortisol metabolism or metabolic rate (e.g. Insulin Dependent Diabetes Mellitus (IDDM), Non-Insulin Dependent Diabetes Mellitus (NIDDM), Hypertension, Hypercholesterolemia, Arthritis, Coronary Heart Disease, and musculoskeletal problems, Cushings Syndrome, anxiety, depression or known psychological mood disorders, high dose oestrogen contraceptive pill ), and if female pre-menopausal and have a regular menstrual cycle of 26 – 30 days.
Exclusion criteria
Not an adult (under 18 years); pregnant; existing in a dependent relationship due to disability; highly dependent on medical care; Aboriginal and/or Torres Straight Islander; involved in illegal activity.
Outcome results
None listed