There are 3,500 calories in a pound of fat. So the most popular rule states if you create a deficit of that many calories, then you shed a pound. However, a recent study has shown there's more to the old formula.
Kevin Hall, who is a researcher at the National Institute of Diabetes and Digestive and Kidney Diseases, said, "Though dietitians use it all the time, making recommendations based off of it, 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 kilo-calories, 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."
‘In 1950s, medical researcher Max Wishnofsky found that a pound of fat tissue represents 3,500 kilo-calories. But, researchers have now found that it over predicts how much people will lose by a sizable margin.’
But, according to Hall, Wishnofsky made a couple spurious assumptions. First, he assumed that when you lose weight you only lose fat tissue. The much bigger mistake Wishnofsky made was misunderstanding how our bodies react to weight loss. As soon as we start cutting calories from our diet, the number of calories our body expends begins to fall. The reason Wishnofsky, and so many others since, have botched this biological fact is that it's fairly counterintuitive.
The tendency is to assume that as you lose weight, the same calorie cut back should prove even more effective once you are lighter, and, presumably, in need of less food. At the very least, it should continue to produce the same results as it was when you were heavier. Hall has, in many ways, spearheaded the movement to shed the nutrition world of the 3,500 calorie rule.
In 2011, he created a model, called the Body Weight Planner, which directly challenged the adage. Drawing from a vast pool of data, the tool approximated metabolic changes in people trying to lose weight, and showed how greatly the 3,500 calorie rule overestimates weight loss.
Hall said, "When we made the comparison between the 3,500 calorie rule and the revised prediction, we found that it over predicts how much people will lose by a sizable margin." Hall prefers to say that losing weight is difficult. Most people who try to lose weight, he says, end up back to where they started in less than a year. But he blames popular but misleading rules for the long-term failure of so many diets.