Second cousins Amy Hill and Suzie Irons have a lot in common: both are registered nurses, both are mothers and both work the night shift.

"It is extremely tough. I wouldn't be doing it unless I had to," says registered nurse Amy Hill.

Working nights is extremely tough on the body. Researchers have long known that shift workers have an increased risk for type 2 diabetes. And now a new study from Boston's Brigham and Women's Hospital may explain why.  

"We all have this internal body clock that primes us for consuming food during the daytime and to be fasting during the nighttime hours. But in shift workers what happens is they actually consume food during the nighttime hours when the body clock is sending them signals which would not be so helpful for processing nutrients," says Dr. Christopher Morris.

Morris explains that staying up all night raises blood sugar. And, this new study finds when a meal is eaten at night, blood sugars rise significantly more than if the exact same meal was eaten in the morning.  

"So people should not only consider what they're eating, but people should also be also thinking about when they are actually consuming their food."