Baby up at night? Inactivity may be a culprit

Napping doesn't help either. In fact, babies who slept less at night, yet napped more during the day, still weren't able to get as much sleep overall as those who slept more at night. Plus, the tired tots weighed significantly more based on their length, indicating a potential risk for early onset obesity.

The research, published in the journal Infant Behavior and Development, is one of the first to focus on the connection between common health behaviors in babies.

"We know physical activity and sleep influence each other and are strongly associated with growth in older children and adults," said Janet Hauck, an assistant professor of kinesiology, who specializes in infant motor intervention research. "Our findings suggest that this association could emerge as early as infancy, a critical developmental period."

Hauck's research centers around the effect physical activity, such as tummy time, has on babies as they grow and develop. Tummy time is exactly that -- the time babies are positioned on their stomachs and encouraged to develop motor skills while supervised.

"While we don't have evidence yet that tummy time directly affects sleep, it increases physical activity and promotes healthy weight gain," Hauck said. "So, parents who feel their baby isn't sleeping enough could promote tummy time during the day to boost their baby's physical activity level."

The study analyzed 22 healthy six-month-old infants and monitored physical activity level and sleep over 24 hours. Weight and length were also measured.

"Babies who slept less overall in the 24 hours and had the least amount of nighttime sleep had more overnight feedings and were significantly less active during the day," Hauck said.

She also indicated that infants who slept longer than 12 hours in a day had a better weight-for-length score, around the 53rd percentile, than those who slept fewer than 12 hours and weighed more.

"Parents can make 12 hours of sleep or more a priority for their baby by creating a bedtime routine and being consistent with it," Hauck said. "While their little one is awake, they should encourage physical activity by interacting with their baby during floor time activities and do supervised tummy time several times a day."