Inclusion Criteria:
Group 1 - Lean, young adults (n = 150)
* Age 18 - 35 years
* Body mass index (BMI) ≥ 18.5 and ≤ 24.9 kg/m2 (≥ 12 months)
Group 2 - Overweight, young adults (n = 150)
* Age 18 - 35 years
* BMI ≥ 28kg/m2 (≥ 12 months)
Group 3 - Lean, older adults (n = 150)
* Age ≥ 60 years
* BMI ≥ 18.5 and ≤ 24.9 kg/m2 (≥ 3 years)
Group 4 - Overweight, older adults (n = 150)
* Age ≥ 60 years
* BMI ≥ 28 kg/m2 (≥ 3 years)
* Subgroup A (n=75): with pre-existent cardiovascular disease defined as: history of myocardial infarction or evidence of coronary artery disease irrespective of revascularization status or history of ischemic or hemorrhagic stroke or presence of peripheral artery disease or heart failure with preserved ejection fraction (NYHA Class I-II).
* Subgroup B (n=75): without pre-existent cardiovascular disease
Group 5 - Nonagenerians Age ≥ 90 (n = 50)
* Age ≥ 90 years
* BMI ≥ 18.5 kg/m2 (≥ 3 years)
Exclusion Criteria:
Group 1 - Lean, young adults (n = 150)
* Highly physical active (i.e. \> 5 times sporting activity / week with moderate to high intensity \[heart rate 140 - 200bpm\])
* Special diets (i.e. ketogenic diet and time-restricted eating)
* Clinically significant metabolic or endocrine disorders
* Claustrophobia
* drug abuse, alcohol \> 15 drinks/week
* Heart failure, cardiovascular disease, immunosuppressive therapies, chronic inflammatory diseases and active oncologic conditions
* Metal implants that prohibit 3T MRI
* Pregnancy or breastfeeding
Group 2 - Overweight, young adults (n = 150)
* Highly physical active (i.e. \> 5 times sporting activity / week with moderate to high intensity \[heart rate 140 - 200bpm\])
* Special diets (i.e. ketogenic diet and time-restricted eating)
* Active anti-obesity treatment (e.g. glucagon-like peptide 1 (GLP-1) analogues, polyagonists, naltrexone and bupropion)
* Clinically significant metabolic or endocrine disorders
* Claustrophobia
* drug abuse, alcohol \> 15 drinks/week
* Heart failure, cardiovascular disease, immunosuppressive therapies, chronic inflammatory diseases and active oncologic conditions
* Metal implants that prohibit 3T MRI
* Pregnancy or breastfeeding
Group 3 - Lean, older adults (n = 150)
* Highly physical active (i.e. \> 5 times sporting activity / week with moderate to high intensity \[heart rate 140 - 200bpm\])
* Special diets (i.e. ketogenic diet and time-restricted eating)
* Diabetes, overt hypo/hyperthyroidism
* Claustrophobia
* drug abuse, alcohol \> 15 drinks/week
* Metal implants that prohibit 3T MRI
* Known severe cardiovascular diseases (i.e. PAD IIa or higher, advanced heart failure = left ventricular ejection fraction (LVEF) \< 35% or NYHA Class III-IV)
* No previous heart failure, cardiovascular disease, immunosuppressive therapies, chronic inflammatory diseases and active oncologic conditions up until the age of 35 years.
* Life-threatening conditions with a life expectancy of less than 1 year or any other condition that would jeopardize proband safety/adherence while participating in this trial.
Group 4 - Overweight, older adults (n = 150)
* Special diets (i.e. ketogenic diet and time-restricted eating)
* Diabetes, overt hypo/hyperthyroidism
* Active anti-obesity treatment (e.g. GLP-1 analogues, polyagonists, naltrexone and bupropion)
* Claustrophobia
* drug abuse, alcohol \> 15 drinks/week
* Metal implants that prohibit 3T MRI
* No previous heart failure, cardiovascular disease, immunosuppressive therapies, chronic inflammatory diseases and active oncologic conditions up until the age of 35 years.
* Life-threatening conditions with a life expectancy of less than 1 year or any other condition that would jeopardize proband safety/adherence while participating in this trial.
Group 5 - "healthy" Nonagenerians Age ≥ 90 (n = 50)
* Claustrophobia
* Clinically significant cognitive impairment compromising study adherence
* Metal implants that prohibit 3T MRI
* Life-threatening conditions with a life expectancy of less than 1 year or any other condition that would jeopardize proband safety/adherence while participating in this trial.
