An analysis indicates a federal study that said obesity is overtaking tobacco as the leading cause of death is full of errors.

The study by the U.S. Centers for Disease Control and Prevention (CDC) released in March inflated the impact of obesity on the annual death toll by tens of thousands due to statistical errors, according to documents reviewed by The Wall Street Journal.

The study, co-authored by CDC director Julie Gerberding and other top CDC scientists, declared obesity as a contributor to preventable death had soared 33% between 1990 and 2000.

However, one analysis contained in internal CDC documents concluded the mathematical errors may have inflated the study's death toll by about 80,000 fatalities, or 20% of the total deaths. If that is the case, the growth from 1990 would have been less than 10%.

Gerberding told the newspaper there had been human errors in the study's calculations, but said they do not diminish the threat that obesity poses to public health.

"The bottom line is that obesity is a leading cause of death," Gerberding said. "This paper in and of itself is a very minor contributor to our knowledge of obesity."