Walking is one of the most popular forms of exercise to keep fit and many walkers, particularly those who want to lose weight, want to know the number of calories that they burned walking.

Unfortunately, the leading standardized equations that are currently used to track the calories burned while walking is relatively flawed. These equations, which have been used for nearly half a century, were only based on data of a limited number of individuals.

In a new study, researchers showed that these leading standards can be improved as they are relatively inaccurate and significantly biased.

Southern Methodist University physiologist Lindsay Ludlow said that the leading standards estimate too few energy expenditures in 97 percent of the cases that they have examined.

Ludlow and colleagues, however, have come up with a new standardized equation that is up to four times more accurate than the leading standardized equations, which assume that one size fits all.

The older equations, which were developed by the American College of Sports Medicine, were based on data from a small set of adult men. Also known as "ACSM" and "Pandolf" equations, these leading standardized equations were initially intended for the military.

Study researcher Peter Weyand, also from SMU, explained why these equations are flawed. He said that the economy of walking on firm level ground is comparable to shipping packages.

"There is an economy of scale," said Weyand. "Big people get better gas mileage when fuel economy is expressed on a per-pound basis."

The researchers said that their new equation can be applied regardless of the weight, height and walking speed of the person and thus, more accurate than the older equations.

The newly developed SMU equations improved the existing standards by taking into account different-sized individuals and using the data from a larger database.

"We adopted a two-step approach to identifying a concise, generalized equation for predicting level human walking metabolism," the researchers wrote in their report, which was published in the Journal of Applied Physiology on March 1.

"Using literature-aggregated values we compared 1) the predictive accuracy of three literature equations: American College of Sports Medicine (ACSM), Pandolf et al., and Height-Weight-Speed (HWS); and 2) the goodness-of-fit possible from one- vs. two-component descriptions of walking metabolism."