Editor's Choice

More miles, fewer biscuits

BMJ 2005; 330 doi: https://doi.org/10.1136/bmj.330.7504.0-g (Published 09 June 2005) Cite this as: BMJ 2005;330:0-g

Unabsorbed calories, an important consideration.


Almost the whole world believes that too many calories and too little
exercise are THE major factors driving the obesity epidemic. Further,
since fat contains over twice as many calories as protein or carbohydrate,
it is ASSUMED that cutting fat calories will prevent obesity. For example,
in Rio state, Brazil, a law banning fat-rich, high-calorie foods in
schools came into effect earlier this year. This action follows a trend
already under way elsewhere in Brazil. The southern states of Santa
Catarina and Rio Grande do Sul also banned high fat foods in an effort to
prevent childhood obesity and promote "healthful" eating habits. This
legislative action was a response to recent disclosure by a government
agency that 1 in 10 Brazilians is Obese due to poor eating habits.
Question is, will low-fat eating prevent obesity? Not likely and here's

In the introduction to her first book, The Schwarzbein Principle,
Endocrinologist Diana Schwarzbein, MD, of Santa Barbara, California
remarks, "Both medicine and the media had promoted the belief that eating
a low-fat diet while increasing complex carbohydrates caused people to
lose body fat and stay healthy. But I had yet to meet anyone who was
healthy or thriving on a low-fat diet." Having already experimented with
having her diabetic patients reduce carbohydrate and add fat to their
diets and seeing them lose weight, Dr. Schwarzbein then "searched the
medical literature, looking for studies showing that low-fat diets are
healthy" and "was surprised that there are no long-term studies showing
such results." Dr. Schwarzbein's clinical experience and journal research
eventually resulted in two books recommending increased fat intake and
decreased carbohydrate intake to normalize hormone balance.

Other independent researchers (among them biochemists, nutritionists,
dentists, medical doctors, etc.) have shown that low-fat diets lead to
hormone imbalance, increased appetite, less brown fat activity, and
increased calorie absorption efficiency. This last matter of calorie
absorption is key to understanding where all the calories go.

Everyone knows that some people can consume high calorie diets
without gaining weight while others cannot reduce body fat no matter how
much they exercise and restrict calorie intake. An interesting example of
high calorie consumption by a sedentary individual that was not resulting
in weight gain was broadcast on USA National Public Radio on November 26,
2004. Mary-Ann Beltran, a low-income single mom was enrolled in a research
project in which every piece of food she ate the day before was
methodically recorded by a researcher, Jenny Donaldson. On the day before
the interview, Ms. Beltran had consumed 6,501 calories as calculated by
Donaldson. Correspondent Patricia Neighmond's remarked that, "Sixty-five
hundred calories is high, particularly when you consider the average daily
caloric intake for women of Mary-Ann's age and height is about 2'000
calories. And although Beltran is not overweight now, at age 34, if she
keeps eating this way, she's at risk." For me, this interview raises two
interesting questions. First, why isn't Beltran already overweight and
second, what reason do we have to suspect that she will ever become

Here's some more interesting observations involving force-feeding
studies. In How To Lower Your Fat Thermostat (1983) by D.W. Remington, MD,
A.G. Fisher, PhD, and E. A. Parent, PhD, the authors report (page 70) that
"In some people, even huge amounts of extra eating will fail to cause
weight gain. These people seem to have a weight-regulating mechanism that
can vigorously defend the selected weight by wasting huge quantities of
excess energy intake." They further observed that any forced weight gain
did not last because "subjects will quickly return to pre-study weight
even though no continuous effort is made to diet."

On page 71 the authors described a case study in which "A German
scientist carefully measured his caloric intake for a full year and noted
that he ate an average of 1760 calories per day." For another year he ate
an extra 400 calories per day and "At the end of the year, he was still
very close to his original weight even though he had eaten enough extra
energy to have gained over 40 pounds. He then increased his intake another
600 calories a day for another year without changing his original weight."

There is a possible explanation for this; unabsorbed calories. The
digestive tract is a tube open at both ends. Muscular contractions propel
food through the tube at various rates depending on the amount of food
eaten and on the amount of soluble and insoluble fiber present in the
food. Since soluble fiber forms a gel in the intestinal tract, it both
slows absorption of digested protein, carbohydrate, and fat into the
bloodstream and prevents some calories from being absorbed altogether.
Consequently, The unabsorbed calories exit the digestive tract in the
fecal material.

Discussion of absorption efficiency on page 78 of How to Lower Your
Fat Thermostat: "There is some evidence that the surface area of the gut
can be increased by food denial to increase the efficiency of
absorption...Rats eating only meal a day have a markedly increased rate of
food digestion and absorption. Many obese people also seem to digest food
more quickly, perhaps because of dietary efforts and periods of food

I've only read a couple hundred books about weight control so I
probably haven't found all existing discussions regarding unabsorbed
calories. Here are a few more sources:

The Bio-Diet / 1982 by Luis Guerra, MD pp 27-28.

Why Calories Don't Count / 1982 by Paul Stitt, MS pp 81-82.(1)

What the Bible Says About Healthy Living / 1996 by Rex Russell, MD p

The Doctors Book of Food Remedies / 1998 by Selene Yeager and the
Editors of Prevention p 419.

Although research regarding unabsorbed calories is scant and mostly
goes unnoticed or is even denied by the scientific community, it is an
important consideration that ought to receive more attention by mainstream
medical and obesity experts because current advice, based on assumed total
absorption of calories into the bloodtstream, is hurting many people who
would benefit from increased fat intake.

Journal references:

(1) A. Antonis et. al., "The Influence of Diet on Fecal Lipids in
South African White and Bantu Prisoners," American Journal of Clinical
Nutrition, Vol. 11, August 1962, pp 142-155.

(2) J.O. Hill, H. Douglas and J.C. Peters, "Obesity Treatment: Can
Diet Composition Play a Role?" Annals of Internal Medicine 119(2):7
(1993): 694-697.

David Brown

Nutrition Education Project

Competing interests:
None declared

Competing interests: No competing interests

15 June 2005
David E. Brown
Nutrition science information analyst
Self employed carpenter residing at 1925 Belmar Dr., Kalispell, MT 59901, USA