Stress increases diet-induced abdominal obesity

“Stress exaggerates diet-induced obesity” which increases belly fat according to a new study by researchers from Georgetown University Medical Center. Animals who were under daily stress and fed a high-fat, high-sugar diet gained about twice as much belly fat as mice who were fed the same diet but were not under stress. Giving a drug which blocked neuropeptide Y2R receptors which are involved in this process reduced abdominal fat by 40 to 50 percent. 

“This tells me it’s not just the stress. It’s the combination of stress and the high-fat, high-sugary rich diet—that is the humongous combo. There is some kind of interaction going on,” Zofia Zukowska of Georgetown University’s Department of Physiology and Biophysics, who led the research was quoted as saying in the Washington Post.

Stress Increases Neuropeptide Y

Stress increases appetite-stimulating hormone, neuropeptide Y

Stress, including exposure to cold and exposure to aggression, causes release of a powerful appetite-stimulating chemical in the brain called neuropeptide Y.

Neuropeptide Y especially increases the desire for carbohydrate-rich foods.

Stress Plus High-fructose Diet Causes Abdominal Obesity

Stress plus high-fat, high-sugar diet leads to abdominal obesity

Stress, either as exposure to cold or exposure to aggression, when combined with a diet high in fat and high in sugar, increased neuropeptide Y in belly fat which led to abdominal obesity and metabolic syndrome.

“This led to abdominal obesity within two weeks and to a metabolic syndrome-like condition after three months,” the authors noted.

“In the long term, stress and a [high-fat, high-sugar] diet lead to gross obesity and symptoms of metabolic syndrome: glucose intolerance, [elevated cholesterol levels, elevated insulin levels, fatty livers and fat in skeletal muscles as well as] hypertension.”

However, giving the mice a drug which blocked neuropeptide Y2R receptors greatly reduced these effects.

“This tells us that [neuropeptide Y] and this [neuropeptide Y2R] receptor trigger the whole process of stress-induced obesity,” Zukowska was also quoted as saying in the Washington Post.
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Conclusion

Conclusion: Stress affects body weight and metabolism

“[O]ur findings provide evidence that stress is not ‘just in the mind’ but rather affects body weight and metabolism,” the paper concluded.

REFERENCE

Kuo LE, Kitlinska JB, Tilan JU, Li L, Baker SB, Johnson MD, Lee EW, Burnett MS, Fricke ST, Kvetnansky R, Herzog H, Zukowska Z. Neuropeptide y acts directly in the periphery on fat tissue and mediates stress-induced obesity and metabolic syndrome. Nature Medicine. 1 July 2007.

AUTHOR’S CORRESPONDENCE

Zofia Zukowska
Department of Physiology & Biophysics
Georgetown University Medical Center
3900 Reservoir Rd. NW, BSB 234
Washington, DC 20057, USA

Technical Information

How stress plus a high-fat, high-sugar diet causes abdominal obesity

For those of you interested in the specifics of how they believe that stress plus a high-fat, high-sugar diet causes abdominal obesity, here is how they think it happens as described in Figure 5 of the paper.

“Stress stimulates release of [neuropeptide Y] and norepinephrine from the sympathetic nerves and secretion of corticosterone [the active form of cortisol] from the adrenal gland.”

Additionally, stress activates an enzyme called Hsd11b1 found in white fat which “converts inactive cortisone to [the active stress hormone] corticosterone and has been implicated in abdominal obesity.”

Like stress, a high-fat, high-sugar diet stimulates release of corticosterone.

Both stress and [a high-fat, high-sugar] diet increases stress hormones in belly fat.

This, in turn, increases the effect of neuropeptide Y on fat cells, and more neuropeptide Y is available for release in response to stress.

This then increases production of fat cells and blood vessels which feed fat cells, and inhibits the release of fat from fat cells induced by adrenaline and noradrenaline.

Stress and a high-fat, high-sugar diet also increase release of adrenaline and noradrenaline which depletes noradrenaline in fat cells.

A continued release of neuropeptide Y and a stimulation of the neuropeptide Y2R receptor directly “leads to abdominal obesity and metabolic syndrome by increasing the growth of abdominal adipose tissue directly, by stimulating its [production of fat cells], and indirectly, by [increasing producttion of blood vessels].”

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