Article explores possible link between obesity and viral infections

Experts don’t dispute the important role that diet and activity play in maintaining a healthy weight. But can poor eating habits and a less active lifestyle fully explain the prevalence of obesity in the United States today? That question has led some researchers to ask whether there might be other causes for this serious problem. In the October issue of Mayo Clinic Proceedings, researcher Richard Atkinson, M.D., asserts that there is a growing body of evidence demonstrating that viruses may play a role in causing obesity in humans.

“The cause of obesity is not a secret -- if you consume more calories than you burn in daily activity, you gain weight. What is interesting is that much of the obesity epidemic cannot be explained just by Americans eating more and exercising less. There are other factors at play, and viruses causing obesity may be one of them,” say Dr. Atkinson.

Dr. Atkinson, director of Obetech Obesity Research Center in Richmond, Va., reviewed multiple published articles that demonstrate a connection between viral infections and obesity. His article in Mayo Clinic Proceedings discusses five animal viruses and three human viruses that have been shown to cause obesity in laboratory studies.

According to Dr. Atkinson, several studies offer ample evidence that animals infected with certain human viruses experience excess weight gain and fat storage. When researchers infected animal subjects with a human virus known as Human Ad-36, they reported measurable increases in the infected animals’ body fat and the visceral fat that surrounds the organs deep within the belly. In addition, studies also demonstrated that infection with Ad-36 and the resulting weight gain could be transmitted from infected animals to uninfected animals.

Information on virus-induced obesity in human subjects is much more limited. Citing his own study conducted in 2005, Dr. Atkinson also showed a connection between obesity and exposure to the Ad-36 virus in humans. Dr. Atkinson’s study screened for antibodies to Ad-36 (a sign of exposure to this virus) in 502 people of varying body weights, both obese and non-obese, from three cities in the United States. Ad-36 antibodies were found in 30 percent of obese individuals and 11 percent of lean individuals. Study results also showed highly significant differences in body mass index (BMI) between antibody-positive and antibody-negative individuals.

Dr. Atkinson also highlighted a study that looked at 89 sets of American adult twins and screened them for Ad-36. Because twins tend to be similar in many characteristics, including body weight, the researchers looked at twin pairs where one twin tested positively for Ad-36 and the other did not.

“Antibody-positive twins were slightly, but significantly, heavier and fatter than their antibody negative co-twins,” says Dr. Atkinson. “The infected twins had a higher BMI and a greater percent of body fat than the uninfected co-twins.”

In the mid-1970s, a virus called SMAM-1 was believed responsible for an increased death rate among commercially raised chickens in India. SMAM-1 is associated with decreased immune function and an increased accumulation of body fat in infected chickens. Dr. Atkinson reports that one study tested 52 obese humans for antibodies to SMAM-1. About 20 percent had SMAM-1 antibodies, indicating exposure to this virus. The study participants who had these antibodies were heavier and had a higher body mass index compared with the antibody-negative group.

Dr. Atkinson’s article also explores what current research has to say about the possible mechanisms underlying virus-induced obesity. Some research suggests that viral infections have a direct effect on adipocytes, cells that manufacture and store fat, turning on the enzymes of fat accumulation and recruitment of new adipocytes.

What’s the next step for this research? According to Dr. Atkinson, “the body of evidence linking adenoviruses to obesity in humans is now sufficient to think about the next step. Ideally, we could prevent infection and virus-induced obesity with a vaccine for the obesity viruses. Development of a human vaccine will take several years.”

Source: Mayo Clinic

Related stories:

Researchers study why high school boys dodge 'Phys Ed'
As obesity and inactivity among youth becomes a growing concern for North American families, new research based at The University of Western Ontario is asking why some high school boys are reluctant to participate in Grade 9 health and physical education classes.
Weight gain may be linked to Ad-3 virus
Blood tests on 2,000 Australians showed about 20 percent had been exposed to a virus called Ad-36, which may be linked to weight gain, a U.S. study finds.
Study finds link between obesity, type 2 diabetes and neurodegeneration
New research from Rhode Island Hospital found that obesity and Type 2 Diabetes Mellitus (T2DM) can contribute to mild neurodegeneration with features common with Alzheimer's disease (AD) – the first study to show that obesity can cause neurodegeneration. The study appeared in the Journal of Alzheimer's Disease Volume 15:1 (September 2008) .
Intellectual work induces excessive calorie intake
A Université Laval research team has demonstrated that intellectual work induces a substantial increase in calorie intake. The details of this discovery, which could go some way to explaining the current obesity epidemic, are published in the most recent issue of Psychosomatic Medicine.
Loneliness undermines health as well as mental well-being
Feeling connected to others is vital to a person's mental well-being, as well as physical health, research at the University of Chicago shows.
New study reveals higher protein breakfast may help dieters stay on track
A new study published online today in the British Journal of Nutrition found that timing of dietary protein intake affects feelings of fullness throughout the day. The study concluded that when people ate high-quality protein foods, from sources such as eggs and lean Canadian bacon, for breakfast they had a greater sense of sustained fullness throughout the day compared to when more protein was eaten at lunch or dinner
Are diabetes and obesity linked to periodontitis?
The University of Illinois at Chicago has received a two-year federal grant to continue a study on how periodontitis, an inflammatory disease of the tissues surrounding teeth, is linked to type 2 diabetes and obesity.
New study assesses the impact of soft drink availability in elementary schools on consumption
The consumption of soft drinks is generally considered to be a contributing factor in childhood obesity. Because children spend a substantial amount of time at school, the school food environment plays a central part in shaping eating behaviors. While the availability of soft drinks in middle and high schools has been investigated previously, a study published in the September 2008 issue of the Journal of the American Dietetic Association systematically assesses how the availability of soft drinks in elementary schools across the United States relates to school-based and overall consumption. A broader question raised by this investigation is how limiting soft drink availability at an early age may alter eating behaviors over time.

News discussion:

Medicine & Health news