Healthy living
Diet and weight loss
Fat chance
Is that burgeoning belly caused by over-indulgence, or are you a victim of a 'fattening' flu virus or the ageing process?
It may not be so easy to dodge the podge if you were unlucky enough to catch the throat infection that can turn stem cells into fat cells, or if you are a post-menopausal woman, according to two new pieces of research presented at this year's meeting of the American Chemical Society.
In the first study, scientists from Louisiana State University took stem cells from the fat tissue of liposuction patients, and introduced half the cells to adenovirus-36 (AD-36) - a known cause of respiratory and eye infections.
After about a week, most of the virus-infected adult stem cells developed into fat cells, whereas the non-infected stem cells did not. Earlier findings by the same team had proved that obese people were much more likely to carry the virus than lean people.
"We're not saying that a virus is the only cause of obesity, but this study provides stronger evidence that some obesity cases may involve viral infections," said Dr Magdalena Pasarica, who presented the study. "Not all infected people will develop obesity," she added. "We would ultimately like to identify the underlying factors that predispose some obese people to develop this virus and eventually find a way to treat it."
The second study investigated whether dwindling supplies of the female sex hormone, oestrogen in the brains of post-menopausal women could disrupt metabolisms, increasing appetite and making it harder to control your weight.
The findings appear to support a connection between oestrogen and regulation of obesity, especially the dangerous accumulation of abdominal fat linked to heart disease, diabetes, and cancer, says Deborah Clegg, assistant professor of psychiatry at the University of Cincinnati Academic Health Center.
"The accumulation of abdominal fat puts both men and women at a heightened risk of cardiovascular disease, diabetes, and insulin resistance," she says. "Women are protected from these negative consequences as long as they carry their weight in their hips and saddlebags. But when they go through menopause and the body fat shifts to the abdomen, they have to start battling all of these medical complications."
In experiments on rats, Clegg showed that when the oestrogen supply was cut off to the brain's ventromedial nucleus or VMN - a key centre for energy regulation - the animals' metabolic rate and energy levels also plummeted.
The animals quickly developed an impaired tolerance to glucose and a sizable weight gain, even when their calorie intake remained the same. In addition, the excess weight went straight to their middle sections, creating an increase in abdominal fat.
Clegg now plans to perform a similar experiment on a region of the brain that puts the brake on food intake as well as stimulating food intake. She anticipates that a loss of oestrogen in this region may create an increase in the animals' appetites as well as their weight.
By identifying the brain regions that determine where body fat is distributed, Clegg hopes her findings may help scientists design hormone replacement therapies to better manage and manipulate oestrogen levels.
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