The wellness industry loves biological 'clocks'. They're a way of using particular measurements in your body (samples from your blood, your cheek cells, your saliva, etc) to get a sense of how old you are, not in actual years, but in physical health trajectory. Research using biological clocks points to a wide range of lifestyle adjustments with the potential to keep you biologically 'young': from supplements , to sleep hygiene , diet , drugs , cultural activities , and exercise . All these