Lose It For Ever – Dave Elger

It has been found in scientific work that a sedentary person can oxidize
31 calories from 1 lb of adipose tissue every 24 hours.

This means that the more fat you carry, the larger your deficit can be,
without catabolized non-fatty tissues (muscle).

Example: A 200 pound man with 20% bodyfat carries 40 pounds of fat, thus
he can maintain 40×31 calories = 1240 calorie deficit per day, without
losing muscle tissue.

Example: A 200 pound man with 5% bodyfat carries only 10 pounds of fat,
thus he can only maintain 10×31 calories = 310 calorie deficit per day.

This is assuming you are sedentary. Adding physical activity will likely
increase the body’s rate of fat oxidation.

My point is simple: the bigger and fatter you are, the bigger your
deficit can be. Large, obese persons can maintain large deficits. The
leaner you get, the smaller your deficit should be.

One more point: eating under your BMR will not INITIALLY halt weight
loss, but if you continue to eat a very low amount of calories for a
prolonged period, your body will fight back

-exerpt from
http://caloriecount.about.com/clarify-maximum-calorie-deficit-ft91383

MY COMMENT: I’ve never seen that 31 calories per pound of fat burned
every 24 hours figure, however the whole theory makes sense- one ideal
calorie deficit does not fit all sizes.

This would be one quick way to take the guess work out if you are a
calorie counter.  You just need to get a body fat assessment (and I can
do that!).

Remember when referring to a calorie deficit, we are talking about a
certain calorie level below what you were doing to maintain your current
weight- including level of calorie intake balanced against total
calories expended.   Go too low or too crazy with exercise and you’ll
drop more lean tissue than you want.

Weight Loss News, Weight Loss Science calorie deficit

You lose fat by creating a caloric deficit over extended periods of time- if the deficit is too large then the body seems to become more efficient at preserving it’s fat stores and weight loss becomes more difficult.   Also, quick weight loss is primarily water and loss of stored muscle glycogen, which is actually quite heavy. 

For this reason, quick weight loss is never recommended.  A calorie deficit of 500 calories per day should result in a pound of fat lost per week.  Depending on how heavy you are, you may see weight come off faster at first.  

One final note- how much weight you lose is irrelevant- what matters most is how much you are able to keep off!   Those who exercise at a moderate intensity for at least 30 minutes per day do much better over time.

Weight Loss Tips calorie deficit, quick weight loss