"Food-induced transcription functions like a metabolic sand timer that runs for 24 hours and is continually reset by the feeding schedule while the central circadian clock is driven by self-sustaining rhythms that help us anticipate food, based on our usual eating schedule," says Vollmers. "But in the real world we don't eat at the same time every day and it makes perfect sense to increase the activity of metabolic genes when you need them the most."

For example, genes that encode enzymes needed to break down sugars rise immediately after a meal, while the activity of genes encoding enzymes needed to break down fat is highest when we fast. Consequently a clearly defined daily feeding schedule puts the enzymes of metabolism in shift work and optimizes burning of sugar and fat.

"Our study represents a seminal shift in how we think about circadian cycles," says Panda. "The circadian clock is no longer the sole driver of rhythms in gene function, instead the phase and amplitude of rhythmic gene function in the liver is determined by feeding and fasting periods ”the more defined they are, the more robust the oscillations become."

While the importance of robust metabolic rhythms for our health has been demonstrated by shift workers' increased risk of developing metabolic syndrome, the underlying molecular reasons are still unclear. Panda speculates that the oscillations serve one big purpose: to separate incompatible processes, such as the generation of DNA-damaging reactive oxygen species and DNA replication.

Panda, for one, has stopped eating between 8 pm and 8 am and says he feels great. "I even lost weight, although I eat whatever I want during the day," he says.

Source: Salk Institute for Biological Studies