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Q: Do raw carrots have negative calories? ( Answered 4 out of 5 stars,   4 Comments )
Question  
Subject: Do raw carrots have negative calories?
Category: Health > Fitness and Nutrition
Asked by: eugenefoss-ga
List Price: $2.00
Posted: 19 Jun 2003 21:10 PDT
Expires: 19 Jul 2003 21:10 PDT
Question ID: 219528
Do raw carrots have negative calories? I've often heard that raw
carrots require more metabolic energy to digest than they produce. Is
this true? I will need a reference to a medical or nutritional
scientific journal, not just a diet book or something.
Answer  
Subject: Re: Do raw carrots have negative calories?
Answered By: politicalguru-ga on 20 Jun 2003 03:15 PDT
Rated:4 out of 5 stars
 
Dear eugenefoss,

I'm afraid this is not true. There is no such thing as "negative
calories", and no food would burn more energy than it consumes. The
idea that such foods exist comes from the "catabolic diet", that
claims so (but is not scientifically substentiated).

Most nutrition experts would also agree, that while vegetables and
especially raw ones, are recommended eating, they do not burn more
calories than they contain or take more energy to digest.

Nicole Jumper, in her review on one of these diets, writes: "In order
for the catabolic diet to work, the human digestive system would have
to be drastically altered.  No living animal’s digestive system is
formatted to give off a reverse thermo result; if so, the species
would not survive.  When a person eats something, his/her body
immediately begins to break the food down and turn it into energy to
be used or stored.  The first process of the digestive system begins
with the actual chewing and tearing of the food.  The salivary glands
provide moisture in order for the food to be tasted, but they also
produce an enzyme in the saliva that begins to digest starch.  After
the food is swallowed, it is passed through the pharynx and esophagus.
 Peristalsis allows the food to travel through the digestive system
through a series of “rhythmic” muscle contractions.  This same process
blends the semi-digested food with the gastric juices of the stomach. 
The stomach absorbs little nutrients; rather it is simply a place
where the food is broken down into a format in which the small
intestine can absorb it.  Because the food at this point is very
acidic, the pancreas has to secrete acid-reducing enzymes so the small
intestine can process the material.  Protein and starch digestion are
completed in the small intestine, but fat must be broken down by bile
salts produced in the liver.  Therefore, fat is absorbed in the
“middle one-third” of the small intestine.  The absorption of water by
the small intestine is also coupled by the absorption of vitamins and
electrolytes.  Digestion is furthered by the large intestine in which
more water is absorbed and inhabited bacteria create several vitamins.
 Whatever remains after this process is the “leftover” or feces. 
Feces mainly consist of undigested fiber, inorganic material, water
and bacteria (Brannon and Feist, 440-442).

   The creators of the catabolic diet claim that this process burns
more calories when digesting certain types of food, but it is obvious
simply by understanding how the digestive system works that this
concept is impossible.  According to Arne Astrup, Director and
Professor of the Research Department of Human Nutrition at The Royal
Veterinary and Agricultural University in Denmark (Holly 1999, p.
109), “There is no evidence to support that the differences in dietary
composition exert clinically important effects on energy absorption
and energy expenditure, so the main mechanism of weight reduction
diets is to reduce total energy intake.”
(Source: Nicole Jumper, [Untitled Webpage], Vanderbilt University,
http://www.vanderbilt.edu/AnS/psychology/health_psychology/catabolic.htm
she refers to articles published in
Brannon, Linda and Jess Feist.  Health Psychology: An Introduction to
Behavior and Health.  Belmont, CA: Wadsworth, 2000.).

In the site "20 Questions and Answers on Weight Conrtol", taken from
"The Food Bible" by J. Wills and maintained by the University of East
Anglia, they say "Whole books have been written about so-called
`fat-burning' foods, which are said to releaseenzymes that burn up
fat, and whole books have also been written about `miracle' foods
thattake more calories to digest than they provide in the first place.
Sadly, however, neither theoryholds up under scientific examination."
(Source: http://www.uea.ac.uk/~x514/HEAL/20FAQs.pdf).

I hope that answered your question. If you need any clarification on
this answer, please let me know. I'd be pleased to clarify my answer
before you rate it.

Request for Answer Clarification by eugenefoss-ga on 20 Jun 2003 10:05 PDT
Those are much better links than I was able to come up with!

I guess what I was hoping for doesn't really exist...what I wanted was
an article titled "Reverse Thermogenesis" in the JAMA.  But from what
you've found, it seems like no scientist would bother investigating
what, given an understanding of the metabolic process, is complete
hogwash.

I'm not sure, though, that either of these pages carries the weight of
authority I was looking for.  I couldn't find any other references to
Nicole Jumper or her knowledge of nutrition.  She could be, for
example, someone with a personal vendetta against the catabolic diet
people.  I'm personally convinced, but would some ardent adherent of
the catabolic diet be?

What I was hoping for was an article written by a respected and
well-known nutritionist, doctor, or food scientist on the subject. 
Someone like Dr. Dean Edell or Shirley Corriher, for example.

Could I convince you to look harder?  Thanks, though!

Eugene

Clarification of Answer by politicalguru-ga on 23 Jun 2003 02:31 PDT
Dear eugenefoss, 

Thank you for your patience. 

I have browsed such journals and found several interesting articles,
though they may not be exactly as expected and in any case, there is
no direct research done on the question.

Kant, Ashima et al. investigated [Kant, Ashima et al. "A Prospective
Study of Diet Quality and Mortality in Women." JAMA 2000; 283
(16):2109-2115.] the effectivity of several "fab diets" including the
grapefruit and the cabbage soup diets. Similarly Kennedy, Bowman et
al. [Kennedy, E., Bowman, S, Spence, J. Popular diets: Correlation to
health, nutrition and obesity. J of Am Dietetic Asso 2001; 101:
411-420.] tested the validity of the claims made in popular diets.
Both of them might provide indirect evidences. Another source could be
studies conducted on the validity of low-carb diets - which also raise
the claim of energy-burning metabolism.

"Total energy expenditure (TEE) is the total number of kilocalories
expended per day (kcal/d). About 60% to 75% is resting energy
expenditure (REE), 20% to 30% thermic effect of activity (TEA), and 5%
to 10% thermic effect of food (TEF)" (Source: Can Diet and Exercise
Really Change Metabolism?
from Medscape Women's Health eJournal[TM], requires subscription at
http://www.medscape.com/viewarticle/408808_2 ; see also 5. Horton,
T.J., and C.A. Geissler. Effect of habitual exercise on daily energy
expenditure and metabolic rate during standardized activity. American
Journal of Clinical Nutrition 59:13-19, 1994. Mole, P.A. Impact of
energy intake and exercise on resting metabolic rate. Sports Medicine
10:72-87, 1990). When examining the thermal effect of foods (tef),
that is, the amount of energy utilised in the digestive process,
clinical research indicates that the body utilises about 10% of the
calories consumed in the digestive process. There are several
interesting studies on the issue (not related to your question
directly, but indicating that there could be no situation whereas the
energy consumed is supressed by the energy wasted in the TEF. Le Goff
et al. [Le Goff G, Le Groumellec L, van Milgen J, Dubois S, Noblet J.
Digestibility and metabolic utilisation of dietary energy in adult
sows: influence of addition and origin of dietary fibre. British
Journal of Nutrition 2002 Apr;87(4):325-35.] found no evidences that
metabolic utilisation of dietary energy is little affected by the
addition and origin of dietery fibers. Hill et al. [Hill JO,
DiGirolamo M, Heymsfield SB. Thermic effect of food after ingested
versus tube-delivered meals. Am J Physiol. 1985 Mar;248(3 Pt
1):E370-4. ] suggest, that the majority of TEF arises after the food
reaches the stomach and that very little of TEF is produced by sensory
factors or by the mechanical aspects of eating.


Other articles 
==============
"CABBAGE SOUP DIET NO LUCKY CHARM FOR WEIGHT LOSS, SAYS UF EXPERT"
http://www.napa.ufl.edu/2002news/cabbagediet.htm

Kelly Brownell, PhD,  Weight Loss: What Really Works? with Kelly
Brownell, PhD, http://my.webmd.com/content/article/49/40236.htm
eugenefoss-ga rated this answer:4 out of 5 stars
Those are some interesting articles.  Certainly we've compiled the
most complete survey available on the subject.

Comments  
Subject: Re: Do raw carrots have negative calories?
From: pinkfreud-ga on 19 Jun 2003 22:34 PDT
 
I have not seen the claim of foods having "negative calories" from any
reputable source.

"Despite some diets' claims, it's not true certain foods and drinks
such as celery, green pepper and ice water take more calories to
digest than they contain. Yes, drinking ice-cold water can lower
temperature slightly, but to see that translate to significant calorie
benefits, you'd have to drink about 25 gallons of ice water, says Yale
University's Kelly Brownell."

http://seattletimes.nwsource.com/html/healthscience/134363821_healthvitals11.html

Commercial diet plans that make fraudulent claims of "negative
calories" have run into legal problems in the UK and Australia.
Eventually the US will probably move against such plans, too, but it
takes a very long time before diet frauds are prosecuted in the US.
Subject: Re: Do raw carrots have negative calories?
From: ac67-ga on 20 Jun 2003 05:55 PDT
 
This reminds me of a joking claim that you can lose weight drinking
scotch and sodas.  I was unable to find that exact claim, but have
found the same rationale for losing weight with beer and ice cream
here: http://hbd.org/ford/newsletters/ford1198.html
The premise is that it takes 1 calorie to raise the temperature of 1
gram of water by 1 degree celsius, so if you start with something
chilled to near freezing (or below) your body will expend more
calories warming it to body temperature than are contained in the
food.  The fallacy here is that in the calorie mentioned in the
formula is with a small c and is the unit used in physics.  In
nutrition, the Calorie has a capital C and is also know as the
kilocalorie - because it is really 1,000 of the calories with a small
c used by physicists.  So while they claim it takes 12,000+ calories
to warm a can of beer, that is the equivalent of 12 Calories (or
kilocalories) - far less than the beer contains.
Subject: Re: Do raw carrots have negative calories?
From: politicalguru-ga on 25 Jun 2003 01:57 PDT
 
eugenefoss - 

Thank you for the ratings!!! 

For those still convinced in negative calories, I suggest the
following tasty diet - a beer and ice-cream diet:
http://www.geocities.com/CollegePark/6174/beer-icecream-diet-cold-calories.htm
Subject: Re: Do raw carrots have negative calories?
From: emile-ga on 07 Aug 2003 19:36 PDT
 
While the claim that raw carrots (or celery, or other common foods)
require more energy to digest than they contain seems pretty far
fetched, I found the answering post here even more hyperbolic in it's
claims that

<blockquote>There is no such thing as "negative calories", and no food
would burn more energy than it consumes.</blockquote>

It seems self evident to me that there are substances which you could
ingest where this "negative calorie" relation would hold:
specifically, if it takes E_i calories of energy to ingest something,
and the thing contains E_c calories, then if E_i > E_c there are
"negative calories."  Simply pick something (ie. sand) with zero
calories, and it's guaranteed to be negative assuming the substance is
below body temperature.

Perhaps a more useful citation would be the amount of energy it does
take to chew, move through the digestive tract, create and excreet the
right enzymes to process, and otherwise digest a given amount of some
food.  This would provide some real numbers as to how low the caloric
value of some food would have to be before it really was "negative
calorie."

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