By Gretchen Reynolds, New York Times

Sleep is essential for good health, as we all know. But a study hints that there may be an easy but unrealized way to augment its virtues: lower the thermostat.

Cooler bedrooms could subtly transform a person’s stores of brown fat — what has lately come to be thought of as “good fat” — and consequently alter energy expenditure and metabolic health, even into daylight hours.

Until recently, most scientists thought that adults had no brown fat. But in the past few years, scanty deposits — teaspoonfuls, really — of the tissue have been detected in the necks and upper backs in many adults. This is important because brown fat, unlike the more common white stuff, is metabolically active. Experiments with mice have shown that it takes sugar out of the bloodstream to burn calories and maintain core temperature.

A similar process seems to take place in humans. For the study, published in June in Diabetes, researchers affiliated with the National Institutes of Health persuaded five healthy young male volunteers to sleep in climate-controlled chambers at the NIH for four months. The men went about their normal lives during the days, then returned at 8 every evening. All meals, including lunch, were provided, to keep their caloric intakes constant. They slept in hospital scrubs under light sheets.

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