When he was still a biology undergraduate, Kalsbeek began to study the effects of the time when someone eats a meal on glucose metabolism. He did not publish about it until years later, after his research on hibernation had steered him towards the biological clock once more. Kalsbeek’s central question is how we can use this clock to improve our health. Not only the central, daylight-sensitive clock in the brain plays a part here; the so-called peripheral clocks in our organs are also important.