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Is there any information on what is considered a healthy (and sustainable) weight and body fat % loss? How many pounds/bf% for each week can I compare my results against so that I know I'm making good progress and that the loss I'm experiencing is sustainable and long term.

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Sustainable for how long? And who are we talking about here--a 5'2'' 25-year old hiking woman, or a 60-year old 6' 200'' sedentary man, or a sumo wrestler who just quit the sport? –  Dave Liepmann Oct 1 '12 at 14:52
    
@Dave: 215 lb, 6', 50 year old man (me) - moderately active. I guess I was looking more for % change based on current weight, etc. rather than specific for me. –  Meade Rubenstein Oct 1 '12 at 14:57
    
Part of my point is that there may not be such a number for the general case. –  Dave Liepmann Oct 1 '12 at 15:04
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Do you remember your weight when you were in great shape? That might help you set goals. I arbitrarily decided on 1.5 pounds a month after I retired at 61. I was afraid my old skin would sag and I'd lose too much muscle mass at a higher rate and I had no reason to rush. I dropped from 187 to 151 at that rate and have held at 147-151 for the last 3 years. The skin sag only shows during planks so no 6 pack but my shoulders are awesome in the right light. I also got my cholesterol, blood pressure, etc into perfect ranges and cut my food expenses. "Pounds per week" sounds a little scary to me. –  medmal Oct 3 '12 at 5:11
    
This guy says he lost 140 pounds in ten months, which is a little more than 3 pounds a week. He had huge amounts of fat to lose, though, because approximately 300 pounds at the beginning. –  Dave Liepmann Nov 28 '12 at 15:58
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Your fat storage can only release 69 kcal/kg per day from your fat mass to be consume as energy. If you use up more energy then that it will be taken from somewhere else. Probably muscle mass.

I will make the assumption that the cell itself is not consumed in the process, therefor the only weight contribution is lipids and water. Water mass is far less and pretty constant in comparison to fat. The energy content of fat in adipose tissue is approximatly 9000[kcal/kg]*80% = 7200 kcal/kg.

What this means is that the fat you have on your body dictates how much caloric deficit you can be in before you start losing fat free mass as it is also shown here.

If you weight somewhere around 130kg, with 73kg lean mass and 57kg fat mass. You can use almost 69 * 57 ~= 4000 kcal/day from your fat storage as energy without making too much sacrifice on muscle mass. That can be up to 7 [days] * 4000[kcal/day] / 7000[kcal/kg] = 4kg of fatloss per week. Almost 9 lbs!

  • 90kg, 17kg fat mass, you can use only 69*16 ~= 1200 kcal/day. 1,2 kg (~3 lbs) per week.
  • 85kg, 12kg fat mass = 0.8kg/week. (~1.7 lbs/week)
  • 80kg, 7kg fat mass = 0.5kg/week. (~1.1 lbs/week)

As you approach 5-6% body fat, your estimated maximum loss of body fat approaches 1 lbs.

Conclusion So what we see is that 2-3lbs/week is a good estimate for a normal person to achieve a goal for the duration of a normal diet plan. As you get leaner the rule of thumb is getting harder to keep without starting to lose lean mass. Also if you are obese there are no problems to lose more then the 2-3lbs/week.

These calculation are estimates and should be seen as optimal release, this do not take metabolic adaptation and and other effects like hormonal issues into acount. What it shows is how much you can be in caloric deficit before you start losing muscle mass.

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Do you have a study for the kCal/kg_fat, too? That number is discussed quite controversial on this site. –  Baarn Oct 11 '12 at 10:30
    
The kcal/kg fat I calculated as adipose tissue consist of 80% fat (wikipedia). Free fatty acids is metabolised as 9kcal/g . 1kg [fat tissue] * 80% * 9 kcal/g [energy density of fat] = 7200 kcal per kg adipose tissue. This is of course just the pure hydrolysis to free fatty acids, I don't think that it would be much loss in that process. So the actual number would be at least in that ball park. I can look it up though. –  conMan Oct 11 '12 at 14:11
    
Would be great if you could do so, as there has been a lot of discussion but I have never seen something reliable for any of those numbers. –  Baarn Oct 11 '12 at 15:09
    
I would guess that most derive it from this equation as a form of total potential energy of the fat storage. In that way this calculation is obviously correct. So my equations above should be viewed as potential weight loss, not ACTUAL weight loss. –  conMan Oct 11 '12 at 19:23
    
ncbi.nlm.nih.gov/sites/… . This pretty much is everything I was talking about, someone have later made a simplified model into what I showed above (which I haven't found yet). –  conMan Oct 11 '12 at 20:52
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This is different for everyone and every situation. What might be considered a healthy "weight loss rate" for someone in a certain situation can be totally different for someone else or in another situation.

Providing your body with the right nutrients and get the right amount of exercise will automatically result in your ideal "weight loss rate".

From experience I found that loosing 5 lbs per week is normal for most people if you adjust you lifestyle and eating habits.

Try this: Consume more water rich foods (vegetables and fruit) and limit your intake of sugar and fast carbohydrates.

I'd recommend you to do some research on healthy nutrition an exercise and see how your body is reacting to it. More than measuring your success by your weight loss, I would suggest you to measure your success by how you feel.

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5lbs/week as a prolonged diet? ... please. That is a near ~2000kcal deficit or even more depending on fat mass. Please include something to support that claim. –  conMan Oct 16 '12 at 13:29
    
Welcome to Physical Fitness! Great with your own experience, you can improve your answer with more detail on that (e.g. total weightloss, time & other activities. Also, if possible, add some references. –  FredrikD Oct 16 '12 at 15:37
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