Inclusion Criteria:  Community-dwelling older adults aged 80+ years old. Have intact cognitive function, evaluated by a score ≥ 3 in the short form of the Mini- mental state evaluation (MMSE)14. Signed an informed letter of consent.  Exclusion Criteria:  Have severe organic or mental disease as determined by history Have terminal cancer. Are on chemotherapy. Have a drug and/or alcohol abuse (>50 g alcohol a day). Have been prescribed new medication within 2 months with potential to alter metabolism. Are hospitalized or bed-ridden because they will not be able to perform any of the tasks in the laboratory and movement during the free-living activity would be limited. Those who need assistive devices (including wheelchair, cane, walkers etc..) for lab testing. Those who are unable to speak and read Danish because they will not be able to follow instructions in the laboratory and during the free-living conditions.