The summary written by Tom Venuto from the article published in the International Journal of Obesity is as follows:
* 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 extremely 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 eneregy 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 mangage 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 will 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 a 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 vs lean tissue (which is why weight training and sufficient protein while on calorie restricted diets are absolute musts!)
Tom goes on to add:
If you have very high body fat to begin with, the typical rule of thumb on calorie deficits may underestimate the deficit required to lose a pound. It may also be too conservative and you can also probably use a moderate to aggressive deficit more safely without as much worry about muscle loss, metabolic slowdown, etc. If you are extremely lean, like a bodybuilder trying to get even leaner for competition, you would want to be very cautious using aggressive calorie deficits. You’d be better off keeping the deficit conservative and starting your diet/cutting phase earlier to allow for a slow, but safe rate of fat loss, with maximum retention of muscle tissue. The long and short of it is that its not quite so simple as 3,500 calories being the deficit to lose a pound. Like lots of other things in nutrition that vary from person to person, the ideal amount of calories to cut “depends”…
Read the entire article at: http://www.burnthefatblog.com/archives/2007/09/3500_calories_to_lose_a_pound.php
