Dr. Kevin Hall, an investigator at the National Institute of Health has done some interesting research about the mechanisms regulating human body weight. He recently published a new paper in the International Journal of Obesity that throws a wrench in works of the "3500 calories to lose a pound" idea...

Some of the equations in his paper made my head hurt, but despite the complex math he used to come to his conclusions, his article clearly prompts the question, "3500 calories to lose a pound of WHAT?" His paper also contained a lot of simple and practical tips you can use to properly balance your caloric intake with output, fine tune your calorie deficit and help you retain more muscle when you diet.

Below, I've distilled some of the information into a simple bullet-point summary that any non-scientist can understand. Then I wrap up with my interpretation of how you can apply this in your own fat loss program:

Calculating the calories required to lose a pound and fine-tuning your caloric deficit

* 3500 calories to lose a pound has always been the rule of thumb. However, this 3500 calories figure goes back to research which assumed that all the weight lost would be adipose tissue (which would be ideal, of course).

* But as we all know (unfortunately), lean body mass is lost along with body fat, which would indicate that the 3500 calorie figure could be an oversimplification.

* The amount of lean body mass lost is based on initial body fat level and size of the calorie deficit

* Lean people tend to lose more lean body mass and retain more fat.

* Fat people tend to lose more body fat and retain more lean tissue (revealing why obese people can tolerate aggressive low calorie diets better than already lean people)

* Very aggressive low calorie diets tend to erode lean body mass to a greater degree than more conservative diets.

* whether the weight loss is lean or fat gives you the real answer of what is the required energy deficit per unit of weight loss

* The metabolizable energy in fat is different than the metabolizable energy in muscle tissue. A pound of muscle is not 3500 calories. A pound of muscle yields about 600 calories.