Worry weight

Stress at the wrong time causes fat cells to flourish

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Get a good night’s sleep if you want to avoid gaining weight. That’s one lesson from new Stanford research on what spurs the development of fat cells. The scientists found that your legions of precursor fat cells are more likely to turn into actual fat if your body’s levels of glucocorticoids — mainly the “stress hormone” cortisol — rise at night.

The same applies if your sleep patterns are interrupted or if you take nighttime doses of glucocorticoid drugs, which are used to treat rheumatoid arthritis, among other diseases.

The research suggests weight gain could be controlled by regulating the timing of pulses of glucocorticoid hormones, says Mary Teruel, PhD, assistant professor of chemical and systems biology and senior author of the study published April 3 in Cell Metabolism.

Researchers have long known that glucocorticoids trigger precursor cells to convert to fat cells, and that our fat tissue contains a huge excess of precursor cells that can convert, given the right signals. They’ve also known that at certain times of day our bodies are awash with glucocorticoids. Normally a person’s levels of glucocorticoids rise and fall in a 24-hour cycle, peaking around 8 a.m., dropping to their lowest around 3 a.m. the next day, and then rising to their peak again about five hours later.

Hence Teruel’s puzzlement: “Why aren’t we drowning in fat every time glucocorticoid levels go high in the morning? And why is losing the normal rhythm of glucocorticoid secretion — such as in conditions of chronic stress, jetlag and sleep disruption in shiftworkers — so linked to obesity?”

Teruel’s team’s research has an answer: Fat-cell maturation ramps up if the trough in stress-hormone exposure lasts less than 12 hours — for example if you are up at midnight worrying. Chronic exposure also gets fat cells going. However, short bursts of the hormones during the day don’t have an impact.

“Our results suggest that even if you get significantly stressed or treat your rheumatoid arthritis with glucocorticoids, you won’t gain weight, as long as stress or glucocorticoid treatment happens only during the day,” Teruel says. “But if you experience chronic, continuous stress or take glucocorticoids at night, the resulting loss of normal circadian glucocorticoid oscillations will result in significant weight gain.” 

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Rosanne Spector

Rosanne Spector is the editor of Stanford Medicine magazine in the Office of Communications. Email her at manishma@stanford.edu.

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