Sources and Mechanisms of Energy Compensation

Excess energy, obesity and obesity-related diseases are important global health issues. Although it is known that obesity is an issue of energy balance, the components of energy expenditure seem to be inter-related in complex non-additive ways. The aim of this study is to explore the downstream impacts of exercise on short term changes in both expenditure and energy intake. The primary question the investigators are asking is whether moderate to high intensity exercise influences the basal energy expenditure and/or energy intake/macronutrient preference in young adult males? (A similar study will be performed on females in a different registration). The investigators will use a specially designed feeding table to measure energy intake and macronutrient intake, which is easy to quantify intake compensation. Basal metabolism will be measured by hood indirect calorimetry. The investigators will explore the factors that influence the level of compensation in expenditure and intake, in particular body composition. Participants will be asked to come to the lab after 10 hours fast for body composition tests including Dual Energy X-ray Absorptiometry(DXA), Magnetic Resonance Image(MRI) and Bioelectrical Impedance Analysis(BIA). They will then be asked (not) to do 30 minutes of moderate-to-vigorous exercise after an energy-limiting breakfast, during which metabolic rate levels and changes in dietary composition will be recorded by gas exchange and standardized buffet. In addition, participants' subjective hunger and preferences will also be recorded by questionnaires. Venous blood will be collected to measure metabolic and hormone factors, blood glucose will be measured by Continuous Blood Glucose Monitor (CGM).

81 participants will be recruited by posters and Wechat. The sample size is calculated using the paired t-test in power analysis, in which α value is 0.05, β value is 0.8, standard deviation is 372 (calculated from the energy intake data in the preliminary trial), and the difference is 108. The alternative hypothesis is greater than 108. The experiment lasted for 14 days, of which two and a half days will be carried out in the laboratory, and the other time only need to wear devices and live freely, which will not affect the normal life. The experiment is mainly divided into three parts:

1. Body composition: Items include weight, height, body fat mass (MRI), bone mass (DAX), body density (BODPOD), lean mass (MRI) and 3D parameters (3D scan). The participants will be required to fasting for at least 10 hours. After the test, they will be equipped with continuous glucose monitoring equipment (CGM), motion monitoring equipment (GT3X) and ambient temperature monitoring equipment (ibutton).
2. Controlled trial: The specific detection contents include resting energy expenditure (REE), active energy expenditure (AEE) and energy intake. The investigators will provide participants with three meals, as an energy restricted breakfast, a standard lunch and supper for dietary component testing. The subjective hunger and eating preference rate of participants will be measured by Visual Analogue Scale (VAS) and questionnaires. Non-physical activities such as working, reading and watching movies will be allowed during the experiment. Venous blood will be collected at several specific points (fasting 10 hours, after breakfast, before lunch and after lunch). In addition, sweat, urine and feces will also be collected.
3. Exercise trial: The schedule is the same as the control trial except for Blood drawing time and 30 minutes of power bike after breakfast, the intensity is 100 watt with 1 minute 25 watt break every 5 minute during the exercise. Venous blood will be collected at several specific points in time (just after exercise, before lunch and after lunch).

Eligibility Criteria:
Inclusion Criteria:

* Healthy adults (men)
* 18-40 years old
* BMI (body mass index)≥18.5 kg/m2

Exclusion Criteria:

* Those who have undergone surgery in the past 6 months.
* People are requiring long-term medication.
* People have metabolic diseases, like diabetes, hypoglycemia, gout, osteoporosis, et al.
* People have digestive diseases, like gastric ulcer, pancreatitis, Intestinal obstruction, et al.
* People have sports injury, like fracture, Joint injury, et al.
* Those who have recently lost weight for various medical reasons (e.g. cancer, etc.).
* People are losing weight by tablets.
* People are suffering from infectious diseases (e.g. HIV, etc.)
* People have blood phobia, pathological hypo or hyper tension.
* People with impaired glucose tolerance.
* Those who are afflicted with claustrophobia.