Calories in, calories out. We’ve all heard this basic,
fundamental calculation regarding weight loss and weight gain. To lose weight,
we must expend more calories than we take in. Consume more than you need, and
the result? The pounds go on. Turns out, lack of sleep may increase daily
calorie consumption, and contribute to weight gain. 

Tired and eating needs creditsThere is a tremendous amount of evidence
that sleep plays an important role in weight management. Insufficient sleep is
strongly linked to obesity and metabolic disorders, as well as to diabetes. But
we’re still working to understand the underlying mechanisms by which sleep can
influence weight. 

A new study examined
the effects of insufficient sleep on weight gain, and looked specifically at
energy intake (calories in) and energy expenditure (calories out). Researchers investigated the
effects of sleep on these two critical factors in weight management. What did
they find? During periods of insufficient sleep, people increased their calorie
consumption and as a result gained weight. What’s more, people who slept too
little consumed more of their calories later in the day, which may further
contribute to weight gain. 

Researchers included 16 adults in a 14-15 day inpatient
study. All volunteers were in good health, and at a healthy weight.
Participants spent the roughly 2-week study period in a controlled environment,
where researchers could manage and monitor their sleep and eating patterns.
Researchers collected baseline health and weight measurements from all 16
volunteers during the study’s first 3 days. During this time participants were
allowed to sleep to a maximum of 9 hours per night. Their eating was regulated
during this 3-day period so they were only consuming what they needed to maintain
their initial weight. 

Next, researchers split participants into 2 groups. One
group continued to be allowed to sleep for as much as 9 hours nightly. The
other group was limited to 5 hours of sleep per night. They slept this way for
5 consecutive nights, in a sleep pattern designed to mimic a typical workweek.
During this 5-day period, both groups were allowed the same unrestricted access
to food. Participants were allowed to eat larger meals, and were given free
access to snacks between meals. Snack foods included both low-calorie options
like fresh fruit, and high-calorie, high-fat choices such as chips and ice
cream. After 5 days, the groups switched sleep schedules, for another 5-day
cycle. During both 5-day phases, researchers conducted measurements and
analysis of participants’ sleep and their energy expenditure. 

Their results shed light on the relationship of sleep to
calorie consumption and output, and on some of the ways that sleep may
contribute to weight gain. Researchers found: 

  • Participants
    whose sleep was restricted to 5 hours a night for 5 consecutive nights
    burned 5% more overall calories daily than those who were allowed to sleep
    up to 9 hours per night. However, the daily calorie intake of restricted sleepers was 6% higher than longer
    sleepers. The result? An energy imbalance for restricted sleepers, with
    more calories consumed than used. 
  • This
    energy imbalance led to an average weight gain of almost 2 pounds for
    those in the restricted sleep phase. 
  • The
    5-day restricted sleep pattern also resulted in alterations to
    participants’ circadian rhythms: the onset of nighttime melatonin release
    was delayed, and wake times occurred earlier. 
  • Eating
    patterns also changed among participants in the 5-hour nightly sleep
    phase. People ate less early in the day, and pushed more of their eating
    to evening hours. In particular, people whose sleep was restricted snacked
    more at night. Evening snacks increased to the point where the calories
    consumed in these late-day snacks exceeded the calories consumed in any
    single meal during the day. 
  • When
    people moved from restricted sleep to the longer sleep period, their daily
    calorie intake reduced. In particular, researchers saw a drop in fat and
    carbohydrate consumption. The transition resulted in slight weight loss
    among this group. 
  • Researchers
    found that men and women responded differently to sleep restriction, with
    regard to weight. Overall, women were able to maintain their weight during
    the 9-hour nightly sleep phase, during which they had unrestricted access
    to food. Men, on the other hand, were more likely to gain weight in this
    phase. But in the restricted-sleep phase, women were more likely to gain
    weight than men. 

These results strongly align with other recent research on
the impact of poor sleep on weight. In particular, we’ve seen other studies
suggest the restricted sleep may make it more difficult for people to choose
healthful foods, and that lack of sleep may contribute to a shift in calorie
consumption to later in the day, to the detriment of our waistlines. 

  • A pair
    of recent studies indicates that sleep deprivation causes neurological
    changes that may compromise judgment and trigger desire for unhealthful
    foods. This study
    found that lack of sleep is associated with diminished activity in the
    brain’s frontal lobe, an area that’s critical to judgment and complex
    decision making. Participants who were sleep deprived made different, less
    healthful food decisions than those who were not. And in this study,
    researchers found that in people who were sleep deprived, the reward
    center of the brain was more strongly activated by unhealthful foods than
    in those who had received sufficient sleep. 
  • This
    2011 study
    examined the timing of sleep and of eating, and their impact on weight. Researchers found that “night owls”—people with late bedtimes—did more of
    their daily eating in the evening, compared to those with earlier
    bedtimes. People with later bedtimes also slept less overall, and had
    lower quality sleep. Night owls consumed more calories at dinner and after
    8 p.m. than those whose bedtimes were earlier. 
  • A study of mice found that
    alterations to a circadian-linked gene involved in hunger regulation
    caused the mice to become obese. Disruptions to this “clock gene” also
    altered the timing of the mice’s eating, causing them to consume more
    calories during the period normally reserved for rest. 

The challenge of maintaining a healthy weight is a
daily endeavor, made up of many small choices—What to eat? How much? When?—that over time have a powerful
cumulative effect. A strongly routine of sufficient nightly sleep can aid in
this endeavor, helping your body and mind work at its best, every day, for
weight control and overall health.

Sweet Dreams,

Michael J. Breus, PhD 
The Sleep Doctor®

The Sleep Doctor’s Diet
Plan:  Lose Weight Through Better Sleep

Everything you do, you do better with a good night’s sleep™ 
twitter: @thesleepdoctor  @sleepdrteam

Click here to sign up for Dr. Breus’
monthly newsletter

Image courtesy of marin at