Could getting a good night’s sleep really help you lose weight? Studies continue to suggest that the answer is yes.

In one of the more recent studies, researchers from the University of Murcia in Spain found that poor quality sleep was linked to a higher body mass index (BMI) in a sample of 2,150 adult twins (1). The association was strong regardless of age, gender, education level, physical activity, or smoking habits.

Previously, other large population studies confirm a consistent relationship between a higher BMI and poor quality sleep (2-8). While most of these studies are observational, the scientific literature suggests that poor sleep is linked to greater weight gain.

Chicken Versus Egg: Does Poor Sleep Cause Weight Gain or Vice Versa?

One area of controversy from the epidemiological research has been whether it’s poor quality sleep that leads to weight gain, or if weight gain causes poor quality sleep. The latest twin study from Spain sought to find clues for answering this chicken-versus-egg question.

When the researchers evaluated twins who didn’t share the same BMI, they found a clear link between poor sleep quality and those with a higher BMI. But when they evaluated twins whose sleep quality differed from each other, a link didn’t appear significant with those with a higher BMI as having poor sleep.

From the research, the scientists suggested that poor sleep quality could strongly influence a higher BMI, not the other way around. The use of twins helped to control for possible confounding factors, such as genetics and environment.

Improving Sleep Quality Measures

Scientists rely on a number of criteria to measure sleep quality. These criteria include the length of time it takes to fall asleep, sleep duration, the percentage of time spent asleep versus lying in bed, sleep disturbances, the use of sleep aides (medication), and daytime dysfunction from lack of sleep (9).

There’s no single cause of poor sleep. Genetics, hormones, poor eating and exercise habits, or irregular working hours could all be factors.

Scientists don’t yet understand how poor sleep might cause weight gain. It may be due to changes to metabolism and hormones (10), along with increases in appetite and hunger (11). Or, it might be related to the types of foods people eat late at night (12), or how the body handles food metabolically at nighttime (13).

Regardless of what the cause is for weight gain, the scientific literature suggests that sleep quality should be a priority for those seeking weight loss. Strategies for getting a good night’s sleep might be taking a quality melatonin product, having a satisfying and nutritious snack before bedtime, and keeping your bedroom dark – with phone and tablet screens turned off.


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