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Can low carb dieters eat all they want, and still lose weight?


"The Atkins Nutritional Approach counts grams of carbohydrates instead of calories... If you are losing weight, there is no need to concern yourself with counting calories. "

Source: atkins.com


You might be doubtful and chances are that mainstream diets are the reason. Of course you couldn't avoid opinions like the below Q&A posted by Health Care Reality Check:

Q: Can a person eat unlimited calories, and still lose weight, as long as they severely restrict carbohydrates?

A: No, she can not. The basis of ketogenic diets, such as the Atkins Diet, is a severe restriction of carbohydrate calories, which simply causes a net reduction in total calories. Since carbohydrate calories are limited, intake of fat usually increases. This high fat diet causes ketosis (increased blood ketones from fat breakdown), which suppresses hunger, and thus contributes to caloric restriction. -- Ellen Coleman, RD, MA, MPH

Is this a correct answer?

Let's first discuss whether it's a correct question. Or, rather, is this the real question so frequently asked by dieters. In my experience, this in fact sounds a little bit different but this makes ALL the difference.

This is what real dieters ask:

Q: Can low carb dieters eat all they want, and still lose weight as long as they only eat allowed foods?

A: Yes, they can. The basis of ketogenic diets, such as the Atkins Diet, is a restriction of carbohydrate-containing foods in favor of fat and protein containing foods, which causes the state of ketosis resulting in significant decrease in appetite. Since appetite decreases, most of low carb dieters consume significantly less calories WITHOUT INTENTIONAL CALORIE RESTRICTION.

Is there scientific evidence?


There is.

Study #1 by: Bassett Research Institute in
Cooperstown, NY and Durham (N.C.) Veterans Affairs
Medical Center.

Reported: Proceedings of North American Association
for the Study of Obesity, Oct. 29, 2000, Long Beach,
Calif.

Who participated:

18 obese men and women with 30 or more pounds to lose.

Average calorie intake before the study: 2,481
calories a day

Method:

Dr. Atkins' Book, the "New Diet Revolution" used as
instruction for the dieters.

Results:

1. Calorie intake during the most restrictive
induction phase (when only 20 g of carbohydrates were
allowed) was 1,419 calories a day on average and weight loss
was more than 8 pounds on average.

2. Calorie intake during the ongoing weight-loss
phase (when carbohydrate intake is being increased
gradually, by 5 g a day) dieters ate an average of
1,500 calories a day and lost an additional 3 pounds
in two weeks.

3. The calorie reduction was attributed almost
completely to carbohydrate abstaining. Intake of fat
and protein remained practically the same as before
the diet.

4. After 6 months on Atkins diet, 41 overweight people
lost an average of 10% of their weight. Most dieters
lowered their cholesterol by 5%, but there were a few
whose cholesterol increased.

5. 20 out of 41 dieters continued the program, and
kept the lost weight off for more than a year.

Study #2 by: Harvard School of Public Health.

Reported: American Association for the Study of
Obesity, October 16, 2003

Who participated: 21 overweight volunteers.

Two groups were randomly assigned to either lowfat or
low-carb diets with 1,500 calories for women and 1,800
for men; a third group was also low-carb but got an
extra 300 calories a day.

Method: All the food was prepared at a restaurant in
Cambridge, Massachusetts. Note that most earlier
studies including the above Study #1 simply gave out
diet plans.

So in this study, dieters were given dinner and a
bedtime snack as well as breakfast and lunch for the
next day, which made the setting a carefully
controlled one. Foods were mostly fish, chicken,
salads, vegetables and unsaturated oils. Red meats and
saturated fats were limited (as opposed to traditional
Atkins menus.)

All meals looked similar but were cooked to different
recipes. The low-carb meals were 5% carbs, 15%
protein, 65% fat. The low fat group got 55%
carbohydrate, 15% protein, 30% fat.


Results:

1. All dieters lost weight, but those on low carb diet
lost more than the low fat group -- even while consuming
MORE calories:

- Group on lower-cal, low-carb diet lost an average of 23
lbs.
- Group on same-calories low-fat diet lost an average of
17 lbs.
- Group on extra 300 calories, low-carb diet lost an
average of 20 lbs.

2. Over the course of the study, the group of low carb
dieters who got an extra 300 calories a day consumed extra 25,000
calories. That should have added up to
about seven pounds. But for some reason, it did not.


Discussion:

"It doesn't make sense, does it?" said Barbara Rolls
of Pennsylvania State University. "It violates the
laws of thermodynamics. No one has ever found any
miraculous metabolic effects."


So it violates the laws of thermodynamics, huh? Not so
fast! When it comes to calorie counting, the "calorie
is a calorie" concept is very deceiving.

Let's see what we count when we think we
count calories. When you burn a piece of wood in a
stove, you can directly measure how much heat energy
it produces. Then you can claim that you know how many
calories a piece of wood contains, right? Not exactly.
You should specify what kind of wood it was, dry or
wet, how you burned it, etc. Because if you spent
another material to start the burning, you should
subtract these calories from the total; if the wood was wet you
should take into account the calories that the water
evaporation took. So even with a piece of wood, it's
not that simple.

Now look at a piece of food. You know how they tell
how many calories it contains? Same way they talk
about a piece of wood in a stove. It's the calorie
number that the food would produce by being burnt in a
stove.

Then in addition to the wood's calorie estimation (that takes
into account the dryness, etc.), you should add many
more circumstances: how hard should one chew it
before being able to swallow, how hard one's enzyme
system will have work to digest it, will it influence
the hormones in charge of fat storing? What about its effect on the
hormones in charge of fat burning?

Which chain of reactions will it trigger, activity-wise
or metabolism-wise? Will it make one sleepy, thus
conserving the energy? Ot will it make one jumpy, thus
wasting the energy?

Study #3 by: Laboratory of Applied Physiology,
Graduate School of Human and Environmental Studies,
Kyoto University, Kyoto 606-8501, Japan

Reported: J Clin Endocrinol Metab. 2003
Dec;88(12):5661-7

Method:

Healthy boys, aged 8-11 yr, were examined for resting
energy expenditure and the thermic effect of a meal,
which were measured for three hours after a
same-calorie but high-fat or a high-carb meals.

Results:

There was no changes after high carbohydrate meals but
there was an increase in resting energy expenditure
after a high-fat meal.

If the researchers in the Study #2 would have measured
resting energy expenditure and the thermic effects of the
meals, they would probably have registered the same changes.
Then everybody would make a sigh of relief:
none of the laws of thermodynamics have been violated:
yes, the low-carb dieters COULD INDEED eat more
calories and lose more weight than the low-fat group
while violating no physical laws because -- they just
burnt more, all the time, even at rest. It's that simple.




About the Author

Tanya Zilberter, PhD, is a researcher, health educator, exercise physiologist, and scientific journalist.

In health sciences since 1972, Dr. Zilberter authored several hundred scientific and popular publications, including four print books and more than a dozen of eBooks.

Tanya Zilberter, PhD