You may believe that you eat double because of the stress and you store a double quantity of fat. That's right, except for a little detail: you store four times more fat! That's because stress makes you not only eat more, but also store more from the same food amount, as revealed by a team from the Georgetown University.
"Studies of mice and monkeys show that repeated stress - and a high-fat, high-sugar diet - release a hormone, neuropeptide Y, that causes a buildup of abdominal fat. Manipulating levels of that hormone could melt fat from areas where it is not desired and accumulate it where it is needed" said the researchers.
This research could lead to safe chemicals replacing unapproved chemicals, like Lipodissolve, employed by some doctors to get rid of local fat deposits in some patients. "It could also reduce or eliminate the need for extremely expensive fat replacements used in breast and facial reconstruction and in other surgeries. In the longer term, we might even be able to use it to prevent obesity. This is the real deal," co-author Dr. Stephen Baker of Georgetown University Hospital, a plastic surgeon. "You could take the fat from your buttocks and put it in your breasts and cheeks," said lead-researcher Dr. Zofia Zukowska.
The recent trials have been made on mice, but within two years, human trials could start. The team divided mice into four groups: two on a conventional diet, and two on a high sugar high fat diet. One group from each type of diet was put in cold water for an hour every day, "like the Northern European experience of waiting for a bus with wet feet," said Zukowska. This was a physical stress.
The other groups were placed together with an aggressive alpha male for 10 minutes daily, "like having a bad boss." This was a psychical
stress.
For the individuals fed on the normal diet, "it really didn't matter whether they were stressed or not. They didn't have much difference in weight. If anything, the stressed ones weighed less." she said.
But the stressed mice on the high-calories-diet stored twice as much belly fat in the first two weeks as the unstressed individuals did. In three months, they turned severely obese. Their biopsies revealed high levels of neuropeptide Y (NPY), a hormone found nearly 25 years ago. In the brain, NPY turns on appetite, while in the periphery of the body, it triggers an increase in the size and number of the fatty cells, including the development of blood vessels to support them.
"It makes sense that, in a stressed environment, an animal would want to make and store fat for a future 'fight-or-flight' response. Unfortunately, in modern society, we are not doing much fighting or fleeing, and the fat remains" said neuroscientist Adrian J. Dunn of the Louisiana State University Health Sciences Center, not involved in this research.
The abdominal fat induces metabolic syndrome, affecting 60 million Americans. This boosts the chances of getting diabetes, heart disease and stroke. "It seems a pity that it is this particular depot that is increased with stressors and comfort foods", wrote Mary F. Dallman and Dr. James P. Warne from UC San Francisco.
The team then tried to imitate the process of fat formation by inserting NPY in a slow-release tablet under the skin of mice and monkeys. "In each, the production of new fat was stimulated around the tablet", she said.
Then the researchers inserted human fat in nude mice, which have a depressed immune system and do not reject such transplants. "Normally, this fat is reabsorbed by the animal within a couple of weeks," Baker said. But when the fat was inserted with NPY, 99% of the fat remained on the same place after three months. But when they inserted a slow-release tablet of a molecule inhibiting the cellular receptor for NPY, the fat storage did not take place.
When the molecule was implanted in a fat deposit, the fat "to just melt away," Zukowska said. In less than two weeks, the fat deposit shrunk by half. As the hormone and the receptor are almost the same in mice, monkeys and humans, this gives hope for human trials.
"Furthermore, there is a Northern European population that, due to a genetic abnormality, secretes excessive amounts of NPY when stressed. That population is unusually susceptible to obesity and diabetes. In contrast, a Swedish population with a genetic mutation that lessens the receptor's efficacy is resistant to obesity.", said Baker.
"NPY has been injected into humans with no apparent side effects, but its long-term effects have not been studied. The receptor blockers have never been used in humans, so nothing is known about their safety." warned Zukowska.
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