A message to night owls: There’s news that your bedtime — and those late-night snacks — may be preventing you from dropping those stubborn extra pounds.
A recent study took on an important, and under-examined, aspect of the sleep-weight loss connection: how the timing of sleeping — and of eating — can affect weight. Researchers at Northwestern University examined the effects of sleep timing on diet and body-mass index (BMI), and found that late bedtimes and late mealtimes can lead to less healthful diets and to weight gain.
A group of 52 adults — 25 women and 27 men — spent seven days keeping food logs and having their sleep and waking activity measured by a wrist sensor. The researchers divided participants into two categories of sleepers:
“Normal sleepers” reached the midpoint of their night’s sleep before 5:30 a.m. These sleepers were asleep by shortly after midnight, and woke around 8 a.m. Among the study group, 56 percent were normal sleepers.
“Late sleepers” reached the midpoint of their nightly sleep after 5:30 a.m. They went to sleep in the middle of the night, well after midnight, and woke in the mid-to-late morning. Among the study group, 44 percent were late sleepers.
Researchers tracked the eating habits of these two types of sleepers through the information provided to them from the participants’ food logs. Not surprisingly, “normal sleepers” and “late sleepers” were on very different schedules, in terms of when they ate throughout the day:
Normal sleepers ate breakfast by 9 a.m., lunch at 1 p.m. and dinner at 7 p.m., on average. These sleepers reported being finished with eating for the day by 8:30 p.m.
Late sleepers reported eating their first meal of the day at about noon. They ate again in the middle of the afternoon, and did not eat dinner until after 8 p.m. Late sleepers did not finish their eating for the day until 10 p.m., on average.
What were the consequences for sleeping later and eating later? Researchers found that late sleepers suffered across the board, in terms of the quality and quantity of both their daily sleep and eating:
Late sleepers slept less overall than normal sleepers — an average of more than an hour less per night.
Late sleepers consumed more calories at dinnertime than normal sleepers. They also consumed significantly more calories after 8 p.m.
Late sleepers had poorer quality diets than normal sleepers — they ate more fast food, drank more sugar-laden soda, and ate fewer vegetables.
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