Waking up early is making us fat

Shift work is particularly vicious. Orfeo Buxton, a sleep researcher at Harvard University Medical School, recently led the first study in humans where sleep was disrupted for several weeks to simulate the effects of shift work. The result was metabolic chaos: glucose spiked to levels that could, over time, trigger diabetes, while energy expenditure slumped to the point where subjects would have gained up to 13 pounds in a year.

And the evidence that social jet lag might be a major factor driving obesity keeps mounting: Roenneberg’s team just published an analysis of thousands of sleep records which found a 33 percent increase in obesity for every hour of social jet lag. Sleep loss, says Buxton, triggers a feedback loop that “makes people prefer processed and sugary foods over fruit and vegetables, while leaving them with less energy to exercise.”