Key words: metabolism, ageing, NAD⁺, physical activity, brown adipose tissue, molecular clock

"Promoting healthy ageing. In pursuit of metabolic health through nutritional intervention, physical activity, and the molecular clock"

The general thought is that with a good metabolism you will age more healthily. The aim of this thesis is to find new starting points to improve people’s metabolism, particularly older people. One of the ways to improve metabolism is to improve the functioning of cells’ “power plants,” i.e., mitochondria. Several ways have been investigated that can improve the functioning of the mitochondria, such as taking extra vitamin B3. The effects of exercise in old age and the effects of circadian rhythms on the functioning of the mitochondria have also been studied. Finally, it has been investigated whether taking extra creatine can help to combat obesity. Together, the various studies have led to new insights on the functioning of human metabolism and how metabolism can be improved in order to age more healthily.