# Living off body fat without eating? **URL:** \ **Category:** Factual Questions\ **Created:** [January 29, 2009, 11:35pm UTC](https://boards.straightdope.com/t/living-off-body-fat-without-eating/483636 "2009-01-29T23:35:22Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![Athena](https://avatars.discourse-cdn.com/v4/letter/a/35a633/32.png) [@Athena](https://boards.straightdope.com/u/Athena)\ **Post date:** [January 30, 2009, 2:48pm UTC](https://boards.straightdope.com/t/living-off-body-fat-without-eating/483636/21 "2009-01-30T14:48:07Z")
> [@Rigamarole](#): > > Quite a lot more. Most calculators claim I need 2800-3000 calories a day as a moderately active adult male and I only weigh 180 pounds. The whole 2000 calorie/day “average” is a load of manure. Maybe for tiny women 2000 calories or even a little less works, but 2000 is pretty low-end for most people. Hell your average meal at a restaurant these days is something like 1200+ calories. Just because an average restaurant meal is 1200+ calories doesn’t mean most people need that much. I’m hardly a “tiny” woman - 5’ 6" tall, BMI right under 25 - work out just about every day, and my average need according to most calculators and my own experience is ~2000 calories a day, 1600 if I wanted to lose weight (which I don’t.) And from what I recall, 2000 calories a day is average daily need for women, they use 2500 on most nutrition labels as an average for men. Seems about right to me. Obviously it’s an average, if you’re smaller/bigger/older/younger/more active/less active it’s not accurate. ---
**Author:** ![jimpatro](https://avatars.discourse-cdn.com/v4/letter/j/b9e5f3/32.png) [@jimpatro](https://boards.straightdope.com/u/jimpatro)\ **Post date:** [January 31, 2009, 12:03am UTC](https://boards.straightdope.com/t/living-off-body-fat-without-eating/483636/22 "2009-01-31T00:03:20Z")
That’s “hearty” bullshit. And I agree. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [January 31, 2009, 12:42am UTC](https://boards.straightdope.com/t/living-off-body-fat-without-eating/483636/23 "2009-01-31T00:42:40Z")
> [@John\_H\_1](#): > > The wikipedia article on fat implies that it is turned into into glucose by the body. Am I missing something? > > “Fats are broken down in the body to release glycerol and free fatty acids. The glycerol can be converted to glucose by the liver and thus used as a source of energy.” I stand corrected… it has been a while since I had biochem. What I was misremembering is that some organs in the body cannot get their metabolic energy from fat, the brain being the most notable. ---
**Author:** ![crh88](https://avatars.discourse-cdn.com/v4/letter/c/977dab/32.png) [@crh88](https://boards.straightdope.com/u/crh88)\ **Post date:** [April 24, 2011, 3:05am UTC](https://boards.straightdope.com/t/living-off-body-fat-without-eating/483636/24 "2011-04-24T03:05:02Z")
For those interested in the article: > **[postmedj00315-0056.pdf](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2495396/pdf/postmedj00315-0056.pdf)** Stewart, WK & Fleming, Laura. “Features of a therapeutic fast of 382 days’ duration” (1973). Postgraduate Medical Journal, 43:203-9. ---
**Author:** ![Peremensoe](https://avatars.discourse-cdn.com/v4/letter/p/ce7236/32.png) [@Peremensoe](https://boards.straightdope.com/u/Peremensoe)\ **Post date:** [April 24, 2011, 3:15am UTC](https://boards.straightdope.com/t/living-off-body-fat-without-eating/483636/25 "2011-04-24T03:15:27Z")
> [@si\_blakely](#): > > People in the end stages of Anorexia have no body fat remaining to draw energy from, so their body starts drawing on muscle tissue - leading to organ degradation. In the case mentioned in the documentary, the subject dropped from 450lb to 175lb - he would have had some remaining body fat at the end, and thus never dropped into the muscle/organ breakdown zone. You are saying that starving people will use up _all_ body fat before _any_ of their muscle tissue is lost? ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [April 24, 2011, 2:27pm UTC](https://boards.straightdope.com/t/living-off-body-fat-without-eating/483636/26 "2011-04-24T14:27:17Z")
> [@Cosmic Relief](#): > > The human body requires glucose to operate, and cannot manufacture it from body fat. It can be recovered by breaking down muscle however. If someone went without food for 54 weeks, that means they lost a hell of a lot of muscle (including cardiac muscle as well). > > This is a grossly irresponsible thing to do; that man could easily have died. The liability alone makes it suspect to me, and how did they actually get a man not to eat anything for a year? I would think one would have to be physically restrained 24x7. Now wait a minute. If the body cannot convert fat to glucose, what can it do with fat. If that were true, you could not lose fat, only muscle and other tissue by dieting and I just don’t believe that. I have lost 60 pounds over the last 10 years and I certainly don’t feel any weaker. ---
**Author:** ![IvoryTowerDenizen](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ivorytowerdenizen/32/17937_2.png) [@IvoryTowerDenizen](https://boards.straightdope.com/u/IvoryTowerDenizen)\ **Post date:** [April 24, 2011, 2:43pm UTC](https://boards.straightdope.com/t/living-off-body-fat-without-eating/483636/27 "2011-04-24T14:43:58Z")
Fat can be broken down to enter the ATP (energy) producing pathways downstream of where glucose enters them. Fat gets broken down to small molecules in a different process than glucose does, but they both end up entering those pathways eventually. Glucose, as an intact molecule or broken down differently, also plays other vital roles that fat cannot sub for. ---
**Author:** ![Hazle\_Weatherfield](https://avatars.discourse-cdn.com/v4/letter/h/e9bcb4/32.png) [@Hazle\_Weatherfield](https://boards.straightdope.com/u/Hazle_Weatherfield)\ **Post date:** [April 25, 2011, 8:13am UTC](https://boards.straightdope.com/t/living-off-body-fat-without-eating/483636/28 "2011-04-25T08:13:52Z")
Eat only BRAAAAAIIIIIINS and see what happens. [Previous page](https://boards.straightdope.com/t/living-off-body-fat-without-eating/483636.md?page=1)