# weight loss calculation **URL:** \ **Category:** Factual Questions\ **Created:** [May 12, 2000, 5:52am UTC](https://boards.straightdope.com/t/weight-loss-calculation/19322 "2000-05-12T05:52:49Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Cardinal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cardinal/32/4000_2.png) [@Cardinal](https://boards.straightdope.com/u/Cardinal)\ **Post date:** [May 12, 2000, 5:52am UTC](https://boards.straightdope.com/t/weight-loss-calculation/19322/1 "2000-05-12T05:52:49Z")
A 400 calorie a day deficit is about equal to running three miles. 1lb of fat = 454 grams. 454 x 9 calories/gram = 4082 calories/lb. 4082/400 cal = 10.2 days 10.2 days x 20 (lbs) = 204 days 204 days/30 days = 6.8 months This says it will take almost _7 months_ to lose 20 pounds, even running 3 miles every stinkin’ day! Please tell me there’s something wrong with these calculations. ---
**Author:** ![douglips](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@douglips](https://boards.straightdope.com/u/douglips)\ **Post date:** [May 12, 2000, 6:08am UTC](https://boards.straightdope.com/t/weight-loss-calculation/19322/2 "2000-05-12T06:08:56Z")
What’s wrong with losing weight at less than 4 pounds per month? Afraid you’ll lose motivation half way through? If you don’t keep running, you’ll just gain it back, so you need to ask yourself if this is a life long commitment, or if you just want to lose weight to get a date with that cute chick in Marketing, then in a year when she marries you you can balloon back up to 300 pounds again. If you are doing it for the rest of your life, why do you care how long it takes to lose the weight? If not, why bother running - just choose the dangerous diet du jour and lose all twenty pounds in a month. Just be sure to listen to what your doctor says first. ---
**Author:** ![moriah](https://avatars.discourse-cdn.com/v4/letter/m/b2d939/32.png) [@moriah](https://boards.straightdope.com/u/moriah)\ **Post date:** [May 12, 2000, 6:23am UTC](https://boards.straightdope.com/t/weight-loss-calculation/19322/3 "2000-05-12T06:23:41Z")
Running 3 miles a day burns up more fat than running 3 miles a day. How so? The ‘aerobic benefit’ kicks in.[sup]1[/sup] The aerobic benefit means that even when you stop running for the day, your metabolism has been turned up and you continue to burn more calories at rest than if you hadn’t run at all. Not only that, but you’re probably turning your leg muscles (the largest in your body) into densely compact and lean muscles which burn more fat than the loose and flubbery kind. Peace * * * [sup]1[/sup]Only if you’re actually running aeobically, i.e., your heart rate is at about 75% of maximum and you are breathing deeply and regularly; and you’re doing this 3-4 times a week. ---
**Author:** ![Needs2know](https://avatars.discourse-cdn.com/v4/letter/n/b5e925/32.png) [@Needs2know](https://boards.straightdope.com/u/Needs2know)\ **Post date:** [May 12, 2000, 2:35pm UTC](https://boards.straightdope.com/t/weight-loss-calculation/19322/4 "2000-05-12T14:35:26Z")
Have you even started to run yet? If not, then stop crunching numbers and put on your shoes! There is a science to weight loss but in the end it is also kind of mind over matter. (no pun intended there) Besides you’re at an advantage, men generally are more successful at losing weight than women, or they at least see results more rapidly. Has a lot to do with water retention and muscle mass, body fat ratios. Just do it! Needs2know…You’d be proud of me. I got up at 5:30 this morning, did my modified yoga stretching stuff and 20 minutes of dance aerobics. ---
**Author:** ![Earl\_Snake-Hips\_Tucker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/earl_snake-hips_tucker/32/3269_2.png) [@Earl\_Snake-Hips\_Tucker](https://boards.straightdope.com/u/Earl_Snake-Hips_Tucker)\ **Post date:** [May 12, 2000, 2:50pm UTC](https://boards.straightdope.com/t/weight-loss-calculation/19322/5 "2000-05-12T14:50:06Z")
If you have a target weight in mind, you’ve practically sealed your fate regardless of how you lose weight. You can’t think of it in terms of “What do I have to do to lose X number of pounds.” Instead think of “What _permanent_ (and sustainable) lifestyle changes to I need to make to better my situation?” The trap is that once someone loses the weight they have targeted, it’s back to the same habits that got them where they didn’t want to be to begin with. It has to be permanent. It has to be sustainable (that is, something that you can see youself doing indefinitely). Here are some quick things that come to mind: Eat more meals. Stop eating when you feel full, not when you can’t stuff any more in. Get a little exercise. Walk a mile or two a day. Doesn’t seem like much, but remember–it’s PERMANENT, so it adds up. Eliminate “problem” foods. That is, high-calorie, but “useless” foods, like candy, ice cream, sugared beverages (like colas, tea), etc. And, most fun–really pig out twice a month or so. This lifestyle doesn’t have to Puritanical. Have a personal gastronomic Mardi Gras every once in a while. ---
**Author:** ![Athena](https://avatars.discourse-cdn.com/v4/letter/a/35a633/32.png) [@Athena](https://boards.straightdope.com/u/Athena)\ **Post date:** [May 12, 2000, 3:11pm UTC](https://boards.straightdope.com/t/weight-loss-calculation/19322/6 "2000-05-12T15:11:37Z")
Actually, most dieticians use the rule of 3500 cals = 1 pound. I have no clue where that number comes from, but that’s the number I’ve seen on many different charts, in books, and coming out of dietician’s mouths. The rule of thumb most places advocate is to lose 1-2 pounds a week, and to do so through both diet and exercise. Shoot for exercising off 1500 cals a week, and cutting food intake by 2000 cals/week. This really isn’t all that hard to do. 'Course, it all depends on body type. I know I can exercise 'til the cows come home and I never drop a pound Example: I started a 12 week workout program 5 weeks ago that starts out with 5 hours a week, then goes to 6, and will end up at 7. Most weeks I work out 6 days a week. I have yet to drop a pound doing this, and highly doubt that I will. However, I know if I put myself on a 1400 cal/day diet, I’ll start dropping weight like it’s nothing regardless of if I exercise or sit on my butt all day. I guess it’s just the way my particular body works. btw, using the 1400 cal/day diet, I dropped 20 pounds in about 10 weeks. Wasn’t that hard, either. ---
**Author:** ![Earl\_Snake-Hips\_Tucker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/earl_snake-hips_tucker/32/3269_2.png) [@Earl\_Snake-Hips\_Tucker](https://boards.straightdope.com/u/Earl_Snake-Hips_Tucker)\ **Post date:** [May 12, 2000, 3:26pm UTC](https://boards.straightdope.com/t/weight-loss-calculation/19322/7 "2000-05-12T15:26:44Z")
I don’t know where they came up with that number, either. 9 calories per gram at 454 grams (roughly) per pound = ~4100 calories per pound. Since that’s one significant digit, the true number should be between 8.5 and 9.5. That would give a range of 3800 - 4300. ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [May 12, 2000, 3:32pm UTC](https://boards.straightdope.com/t/weight-loss-calculation/19322/8 "2000-05-12T15:32:16Z")
I don’t know how much of a difference this makes, but don’t forget that if you run to loose weight, your fat cells decrease in size but you are building muscle mass in your legs. So getting on the scale at the end of a week might not yield the exact results you want. Genetics also come into play here as much as they do for fat burning: how densely / quickly do you build muscle mass? The end result is that your girth could be decreasing at a greater rate than your weight. This is bad only if you are planning a hot-air balloon trip. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [May 12, 2000, 5:34pm UTC](https://boards.straightdope.com/t/weight-loss-calculation/19322/9 "2000-05-12T17:34:41Z")
> [@](#): > > \*\* > Actually, most dieticians use the rule of 3500 cals = 1 pound. I have no clue where that number comes from, but that’s the number I’ve seen on many different charts, in books, and coming out of dietician’s mouths.\*\* From _Understanding Nutrition_ by Whitney and Hamilton > [@](#): > > A pound of body fat (adipose tissue) is actually composed of a mixture of fat, protein, and water and yields 3500 kcal on oxidation. A pound of pure fat would yield 4086 kcal. ---
**Author:** ![Phil\_Saoud](https://avatars.discourse-cdn.com/v4/letter/p/779978/32.png) [@Phil\_Saoud](https://boards.straightdope.com/u/Phil_Saoud)\ **Post date:** [May 14, 2000, 2:38am UTC](https://boards.straightdope.com/t/weight-loss-calculation/19322/10 "2000-05-14T02:38:00Z")
> [@](#): > > \*\* > A 400 calorie a day deficit is about equal to running three miles. > > 1lb of fat = 454 grams. > > 454 x 9 calories/gram = 4082 calories/lb. > > 4082/400 cal = 10.2 days > > 10.2 days x 20 (lbs) = 204 days > > 204 days/30 days = 6.8 months > > This says it will take almost _7 months_ to lose 20 pounds, even running 3 miles every stinkin’ day! Please tell me there’s something wrong with these calculations. > \*\* There IS one error in your calculation. It take 9 Calories(which are actually kilocalories) to metabolize one gram of fat. However it only take 4 Calories to metabolize a gram of carbohydrates. Because of this, your body will burn carbohydrates at a faster rate than it will burn fat. This is a nice survival mechanism but it makes it hard to lose weight. As your bodys carbohydrate store depletes, the percentage of fat burned increases. The optimal level of fat burned depends on the duration and intensity of your workout. The standard recommendation is to work out at a low intensity(60% to 65% of your maximum heart rate) for a period of at least 30 minutes. A three mile run every day will have great benefits but it probably isn’t the best workout if your goal is to lose 20 pounds.