(WASHINGTON POST)  Roberto A. Ferdman — There’s a popular rule you’ve probably heard before about losing weight: for every 3,500 calories you shed from your diet, you’ll lose a pound. But just because everyone, including nutritionists with graduate degrees, keep repeating this doesn’t make it true.

In fact, it’s a total myth.

“I see dietitians using it all the time, making recommendations based off of it,” said Kevin Hall, who is a researcher at the National Institute of Diabetes and Digestive and Kidney Diseases. “Unfortunately it’s completely wrong.”

The adage dates back to the 1950s, when medical researcher Max Wishnofsky measured how much energy a pound of fat tissue represents, and found that it was 3,500 kilocalories, otherwise known as calories. Theoretically, he had calculated how many calories a person had to burn—or forego—in order to lose a pound of fat. But Wishnofsky made a couple spurious assumptions.