Most fitness conscious people have heard that there are 3,500 calories in a pound of fat, so if you create a deficit of 3500 calories in a week, you lose a pound of weight. If you create a deficit of 7000 calories in a week, you lose two pounds, and so on. Right? Well, not so fast…
Dr. Kevin Hall, an investigator at the National Institute of Health in Bethesda 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 data 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.
- If you lose lean body mass, then you lose more weight than if you lose fat.
- If you create a 3500 calorie deficit in one week and you lose 100% body fat, you will lose one pound.
- But if you create a 3500 calorie weekly deficit and as a result of that deficit, lose 100% muscle, you would lose almost 6 pounds of body weight! (of course, if you manage to lose 100% muscle, you will be forced to wear the Dieter’s Dunce cap)
- If you have a high initial body fat percentage, then you are going to lose more fat relative to lean, so you may need a larger deficit to lose the same amount of weight as compared to a lean person
- Creating a calorie deficit once at the beginning of a diet and maintaining that same caloric intake for the duration of the diet and after major weight loss fails to account for how your body decreases energy expenditure with reduced body weight
- Weight loss typically slows down over time for a prescribed constant diet (the “plateau”). This is either due to the decreased metabolism mentioned above, or a relaxing of the diet compliance, or both (most people just can’t hack aggressive calorie reductions for long)
- Progressive resistance training and or high protein diets can modify the proportion of weight lost from body fat versus lean tissue (which is why weight training and sufficient protein while on calorie restricted diets are absolute musts!)
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