Gender- and age-dependent effects of caloric restriction on body composition, glucose homeostasis, energy balance and adipose metabolism in overweight and obese adults: a controlled dietary intervention study comparing younger and older men and women, with an embedded sub-study examining the role of oestrogen hormone replacement therapy (HRT) in postmenopausal women (GendAge Study)
Overweight and/or obesity
Run-in period of 10 days (7 day ad libitum food diary at home and 3 days maintenance diet provided to energy balance). Followed by a weight loss diet for 6 weeks (42days), as a nonrandomised allocation. The study lasts 53 days in total for each participant comprising twenty-two study visits to the Human Intervention Studies Unit (HISU); a screening visit during which potential volunteers will be asked to fill in a health questionnaire at the screening visit to assess their suitability for the study. This is followed by four test day visits (representing pre- and post- dietary phases) and seventeen occasions to collect food and have body weight measured. All food provided to free-living participants is prepared at the HISU by dietetic staff. The study meals are adjusted (scaled) to individual energy requirements based on measured basal energy requirements (RMR – Resting Metabolic Rate). • Phase 1: 3-day maintenance diet (MT, fixed macronutrient composition of 15% protein, 30% fat and 55% CHO), fed to energy requirements (1.3 X RMR) • Phase 2: 6-week calorie restricted weight loss diet (CR, fixed macronutrient composition as 30% protein, 35% fat and 35% CHO) fed to energy requirements (0.8 X RMR), with stepwise reduction of 100kcal/d at week 3 and 5 (Days 15 and 29)
Adults (aged over 18years) who are healthy but overweight/obese (BMI 27-45kg/m2): 1. 15 women (age 40 or less years) 2. 15 men (age 40 or less years) 3. 15 women (age 55-65 years) in menopause*; not taking Hormone Replacement Therapy (HRT) 4. 15 men (age 55-65 years) 5. 15 women (age 55-65 years) in menopause; taking HRT** *menopause definition is no menstrual period for 12 months **HRT inclusion criteria - women will have continuously taken oestrogen HRT for 24 months
Medication exclusion criteria, current use: 1. Weight loss medication (e.g. GLP agonists), β-blockers, antihistamines, antipsychotics, benzodiazepines, barbiturates, melatonin, Ritalin, modafinil, soporifics, hypnotics, antiepileptic drugs, diabetes medication (e.g. metformin or insulin). Self-reported medical exclusion criteria: 1. Females who are planning to be pregnant, are pregnant or are breastfeeding 2. Coeliac disease or gluten intolerance or food allergy 3. Diagnosed T1 or T2 diabetes 4. Suffering from a psychiatric disorder or any type of substance abuse Other exclusion criteria: 1. Vegetarian or vegan diet 2. Following a weight loss programme (that may be affecting lifestyle, physical activity & diet) or undergone gastric band/reduction surgery; including GLP agonist (e.g. Semaglutide injection, Ozempic®) 3. Currently participating in another research study 4. Unsuitable veins for blood sampling 5. Unable to fluently speak, read and understand English 6. Unable to comply to an alcohol-free diet for 6 weeks 7. Unable to give fully informed consent