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I keep reading that the guideline to shoot for is a max of two pounds a week for weight loss. Why?

You see these folks on TV being driven to loose 10lbs a week. Is it just the fact they are so obese that they can handle that sort of crazy drop in weight for the short term but will flatten out once they get down to a more 'normal' BMI? Or are they doing some serious danger to themselves?

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The more obese you are, the more you are eating well in excess of your daily food requirements. Many of these morbidly obese contestants are forced to limit their daily calories into a more normal range. That difference is so drastic that they can't help but lose up to 2 pounds a day. We're talking a difference between 10,000 Calories and 2,000 a day. We are not talking about the difference between 2,000 and 500 Calories a day. –  Berin Loritsch Sep 18 '12 at 17:47
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4 Answers

The greatest predictor of future weight gain is past weight loss. If you try to cut weight that quickly, you're likely to be a part of that statistic.

If you're losing a significant amount of weight over a short period of time, chances are you're losing muscle instead of, or as well as, fat. This might be a contributor to the above mentioned weight gain predictor. If you cut a bunch of weight, but it's mostly muscle mass, when you gain that muscle mass back, you'll also gain some fat with it, and suddenly you're heavier than before.

Rapid weight loss can also be water loss, which is to say, dehydration. That's not good for you either.

Really, if your goal is to lose fat, which if you have a ton of it, isn't a bad idea (if you're just in the 'overweight' category, I wouldn't worry about it unless you actually feel unhealthy), I would shake any notion of "weight loss". I would replace it with a goal of losing inches, and reducing body fat percentage. This allows for weight gain, due to added muscle, while losing fat. That's more likely to be sustainable. Muscle loss isn't sustainable - you'll eventually crash and have to build it back up (or be perpetually unhealthy; another likely contributor to the negative health effects associated with being overweight or obese is unhealthy weight loss practices).

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A slight correction (same conclusion) to your second paragraph is that with less muscle mass, you have a lower resting metabolic rate, which means the same calories you used to eat to maintain will now cause you to gain weight. –  Berin Loritsch Sep 18 '12 at 16:10
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I also completely agree with your last paragraph. So I'll add my +1 here. –  Berin Loritsch Sep 18 '12 at 16:11
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Consistently losing more than 2 pounds per week means you're losing lean body mass (muscle). Lean body mass is what requires calories to operate. If you decrease your lean body mass, and you'll need fewer calories to maintain your weight. So, losing muscle almost guarantees rebound weight gain.

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can you add any sources for this? –  FredrikD Sep 26 '12 at 13:26
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The major concerns are as follows:

  • What goes away quickly can come back quickly
  • You can lose muscle faster than fat on starvation diets--which feeds and perpetuates eating disorders.
  • If you don't eat enough to support your metabolic processes, you can cause serious health issues.

There are a couple common exceptions to the 2lb/week rule:

  • An athlete may dehydrate themselves and cut back on carbs to make a target weight class. If you try and loose too much water weight, it will negatively affect your performance--so most athletes don't push it to dangerous levels. After weigh-in, they refeed and rehydrate, getting back to their pre-cut weight.
  • Ketosis based diets can burn fat at a more rapid pace for the first few weeks while still providing enough essential nutrients (both macro and micro) to support your metabolic processes. This rapid fat loss tapers off over time, and you will likely settle in to the more normal 1-2lbs a week rate eventually. Hydration is very important on these diets to prevent keto-acidosis.

Note that in both of these cases, the glycogen stores are depleted. This affects the energy you have available for exercise or competitions. It also accounts for up to about 5lbs of weight. This is why after coming out of ketosis you will have a one time weight gain of around 5lbs. Emptying the glycogen stores only takes about 3 days even when you don't exercise.

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So if I'm eating between 1500-2300 healthy calories a day and working out for about 45-60minutes 5-6 times a week in Zone 3 with additional weight training, should I be concerned if I've dropped more than 2lbs a week on average? I'm presuming things will level off eventualy as fitness increases and body weight decreases. Been going hard all summer and lost about 20lbs (5'8 @ 260lb now 240lb) in 7-8 weeks and aside from some having hungry days I feel great. I was aiming for a 2lb/wk loss but it's coming off faster than expected. I've lost about 8 inches off the waist in same time frame. –  Chef Flambe Sep 18 '12 at 19:35
    
There's a lot of factors that go in to what is right for your body. You probably underestimated the energy your body needs given all the work you are doing, which is a rarity. Assuming you are a male @ 260lbs, you should probably keep your minimum around 1800 Calories--particularly if you feel lightheaded or find it hard to concentrate during the day. –  Berin Loritsch Sep 18 '12 at 21:19
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2lbs a week is a bit of a blunt instrument and obviously a small woman weighing 100lbs would be different from a man weighing 260lb

20lbs in 7.5 weeks is 2.6lbs/week so you are not far off the 2lbs a week. This works out as 1% of your body weight. So I wouldn't worry about it.

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