Proactol Blog

Discovering the “Sleep and Size” Connection

Obesity is a disease that, in just the past few decades, has been rising dramatically in developed countries and reached epidemic levels in the United States and United Kingdom.

In addition to the social consequences attached to obesity, these rapidly rising numbers are cause for concern because of the risks of secondary complications, including insulin resistance and type 2 diabetes mellitus, hyperlipidemia (high cholesterol), cardiovascular disease, hypertension (high blood pressure), stroke, cancer, and arthritis (joint disease).

According to a recent study published in an international clinical journal (Arch Intern Med. 2005; 165: 15 – 16), sleep loss is indeed playing a role in this epidemic. According to the study, obese and overweight patients in a study group reported sleeping less than their peers who had normal body mass indexes (BMIs). Researchers examined patients’ total sleep time per 24 hours in relation to their body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters). The patients were classified as being of normal weight (BMI less than 25), overweight (BMI 25 – 29.9), obese (BMI 30 – 39.9), or severely obese (BMI 40 or greater).

It was found that total sleep time decreased as BMI increased. Men slept an average of 27 minutes less than women, and overweight and obese patients slept less than patients with normal BMIs.

According to another study based on data from the National Health and Nutrition Examination Survey I (NHANES I), people who reported getting less than seven hours of sleep a night were more likely to be obese. Similarly, participants who slept five hours per night were 73% more likely to become obese than those getting seven to nine nightly hours of sleep,

But how?

It has been proved that insufficient sleep causes neuro-cognitive changes such as excessive daytime sleepiness, altered mood, and increased risk for work-related injury and automotive accidents. Speaking of US alone, it has been reported that the average American is currently getting less sleep than they did a century ago. With these declining sleep times, there has also been an increase in the number of both obese and severely obese people.

While more work is needed to explain the sleep-obesity relationship, the researchers have some ideas:

Theory 1: Humans may have evolved to store fat in summer, which has short nights and plentiful food, to prepare for winter’s long nights and historically scarcer food supply. As a result, sleeping less could serve as a trigger to the body to increase food intake and store fat.

Theory 2: Other studies have also shown that insulin sensitivity and levels of two appetite-related hormones — leptin and ghrelin — can be affected by sleep deprivation, which could impact weight. Leptin is associated with appetite control and ghrelin has been identified as an appetite stimulant. During sleep deprivation, leptin levels fall and ghrelin levels rise.

Theory 3: Another theory suggests short sleep leads to low caloric intake and expenditure since sleep deprivation often results in fatigue, daytime sleepiness and low activity levels.

Conclusion

In short, it’s clear from the above discussion that sleep may affect energy balance. Sleep may not be the only answer to the obesity pandemic, but its effect should be considered seriously, as even small changes in the energy balance are beneficial. The more sleep you get a night, the lower your risk of being overweight or obese. Good sleep could be part of the obesity prevention approach.