When we burn the midnight oil because we’re just too busy for bed, it seems reasonable to expect that we would burn extra calories, too. But that’s not what happens. In fact, the opposite is true. As a growing amount of research reveals, skimping on sleep is likely to make the number on the scale climb.

This seems unfair, especially when we’re working so hard to stay slim (another celery stick, anyone?). But we might as well face facts if we hope to avoid getting fat. That’s why I contacted Michael Breus, PhD, author of The Sleep Doctor’s Diet Plan: Lose Weight Through Better Sleep, who explained the various factors that contribute to this connection.

Why sleep loss leads to weight gain…

Appetite-regulating hormones get out of balance. Ghrelin is the “go” hormone that stimulates hunger…and when you’re sleep-deprived, ghrelin levels increase by up to 15%, Dr. Breus said. Leptin is the “stop” hormone that tells you when you’re full…and lack of sleep depletes leptin levels by about 20%, he added. Curious new finding: A study from St. Luke’s/Roosevelt Hospital in New York City found that these hormonal effects differ by sex, with sleep-deprived women being particularly affected by the reduction in leptin and sleep-deprived men being particularly affected by the increase in ghrelin.

Your body goes into stress mode. Loss of sleep leads to stress—and elevated levels of the stress hormone cortisol. This in turn is likely to trigger cravings, particularly for sugary or salty “comfort foods,” such as cookies or chips.

Fat-cell activity goes awry. A new study from the University of Chicago found that when participants got 4.5 hours of sleep per night for four consecutive nights, their fat cells’ response to insulin diminished by 30%. Dr. Breus explained that this decreases the ability of fat cells to properly store and release energy—so the body basically hangs onto calories rather than burning them.

Decision-making ability is compromised. In a study from the University of California, Berkeley, MRI scans revealed that sleep-deprived people had significantly impaired activity in the frontal lobe of the brain, a region critical for making complex choices such as which foods to eat. As Dr. Breus explained it, a well-rested brain is more likely to make well-considered decisions, whereas a too-tired brain is prone to impulsiveness—including poor dietary decisions.


Now that we’ve covered why sleep is so important for weight control, let’s talk about how much sleep we need…and how to get it.

Though individual needs vary, research suggests that women with the healthiest weight-to-height ratio spend, on average, 7.7 hours in bed each night. If you’re not coming close to that, take a look at your daily schedule. You could be sabotaging yourself with activities that interfere with your ability to fall asleep and stay asleep.

Here’s how to adjust your routine…

Exercise early. Regular physical activity promotes proper rest—but don’t schedule your workout within four hours of bedtime or you may be too physically overstimulated to get to sleep.

Eat dinner three to four hours before bedtime. When your stomach is too full, the sleep process has to compete with the digestive process, which can make it hard to get to sleep. But don’t go to bed too hungry, either—hunger elevates cortisol levels, keeping you awake. Dr. Breus’s recommendations: If you need an after-dinner snack, have it at least an hour before bedtime…limit the snack to no more than 200 calories…and include a small amount of protein plus some complex carbohydrates. Good options include yogurt with almonds and granola…or warm oatmeal with milk and banana slices.

Avoid caffeine after 2 pm. Caffeine can stay in your system for eight to 10 hours, so a late-afternoon latte could still be creating a sleep-stealing buzz past midnight.

Don’t drink alcohol within three hours of bedtime. Although a drink might help you fall asleep initially, alcohol reduces rapid eye movement (REM) sleep—so you won’t feel well-rested come morning. Better than a nightcap: Have some herbal tea sprinkled with nutmeg—the spice has been shown to promote slumber.