Can a virus cause weight gain?

Some scientists theorize that certain viruses (microorganisms that cause infections such as colds and flu) can cause excessive weight gain or obesity in animals. Laboratory studies have shown that infecting mice and hamsters with these viruses makes them gain large amounts of weight—a phenomenon called "infectobesity." Whether viruses cause humans to become obese is unknown, however.

In related studies, some intriguing research by Drs. Richard Atkinson and Nikhil Dhurandhar found that infecting animals with a type of virus called the Ad-36 adenovirus caused them to gain weight. When they studied humans, they found that people who had antibodies to this virus weighed significantly more than those who did not.

They also examined identical twins, in whom one had antibodies to this virus but the other did not. The twin with the antibodies to the virus (in other words, who had had a prior infection with it) had 2 percent more body fat than the other twin, even though their genes were identical.

Dr. Atkinson started a company called Obetech that will test you to see if you have the antibody to the Ad-36 adenovirus (for $450). Those who do are more likely to gain weight, so knowing this may help them become more mindful of their diet and lifestyle.

However, many other factors are involved, not just a virus. One of the most useful tests is also the least expensive and most widely available: standing on a scale each day. If you find that your weight is beginning to increase, move a little closer to the healthy end of the Spectrum, as described in chapter 5 of the book, The Spectrum.

Some people believe that the inflammation that is often seen with obesity may be caused by a virus and that the virus causes both the obesity and the inflammation. However, obesity causes inflammation even in people who do not have antibodies to the Ad-36 adenovirus, and this inflammation may play an important role in a number of illnesses, as I described in chapter 3 of the book, The Spectrum.