CATEGORY: biology/metabolism
TECHNICAL: **
SUMMARY:
This document describes the main reason I tell people
that low-carb diets are more effective that fasting, or low-cal
(starvation type) diets. Everyone seems to think that by simply
eating less they will lose weight.. That has simply never been
true. In actuality, dieters should be striving to eat maintainance
level calories and rely on activity to do the job. This keeps
basal metabolism high instead of crashing it and placing you
in "starvation mode".
As you can see below, the net effect of low-cal diets
is to decrease your thyroid output, and hence, your body's overall
energy expenditure. (it gets greedy). This is the first document
I've seen that's actually put a cut-off level on it. Their
study showed that a 1000 cal/day deficit was enough for your body
to turn off metabolism.
Let's do the math.. 1000 kcal/day over 7 days is 7000
kcal/week. 7000 kcal is slightly less than 2 lbs. of fat. (one
lb. of adipose is about 3550 kcal.). THEREFORE, according to
this study, anyone who is losing 2 lbs. a week of weight cannot
possibly be losing fat, and instead, it must be partly muscle
that is being lost as well. (which is about right, as verified
by other sources)
So you see, why bother with killing yourself slowly
with starvation diets? Try the low-carb approach and see if you,
like many others, have a much easier time getting rid of that
extra fat mass on your body. (aside from all of the health
benefits of low carb diets too)

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Resting Metabolic Rate

by Jeff Johnson, MS

[ Jeff Johnson, MS of Performance Fitness & Nutrition is a strength &
conditioning specialist and sports nutrition consultant, specializing in
high performance and post-rehab conditioning. He is the exercise guide for
The Mining Company at http://exercise.miningco.com ]

In general, it appears that dieting decreases RMR, probably due to
losses of muscle in fat-free mass. Some researchers believe that a
permanently reduced metabolism is the reason that diets do not work and
that weight is regained.

Low calorie diets, in of themselves, as well as considerable energy
expenditure (exercise) coincident with inadequate caloric intake have been
found to have an effect on metabolism through reduced T3 hormone
(triiodothyronine) production. This occurs almost immediately and long
before any substantial loss in lean body mass occurs. This occurrence is
sometimes referred to as the "starvation response".

In a study on young women who exercise, it was found that T3
production was suppressed when "energy availability" fell below a 1,000
calorie-per-day level (Loucks 1994). "Energy availability" is the amount
of energy available after subtracting caloric expenditure in exercise from
daily caloric intake.

The body is trying to conserve energy in a calorically restricted
state. Thyroid hormone production and secretion decreases in an attempt to
reduce basal metabolic rate and increase one's energy efficiency.

Hypothyroidism often occurs coincident with diet-induced amenorrhea.
Similarly, amenorrheic athletes frequently have depressed thyroid hormone
concentrations compared to women with regular menstruation while training
in a similar manner (Loucks 1992).

Loucks AB, Laughlin GA, Mortola JF, Girton L, Nelson JC, Yen SS.
Hypothalamic-pituitary-thyroidal function in eumenorrheic and amenorrheic
athletes. Journal of Clinical Endocrinology and Metabolism 1992;
75(2):514-518.

Loucks AB, Callister R. Induction and prevention of low-T3 syndrome in
exercising women. American Journal of Physiology 1993; 264(5.2):R924-30.

Loucks AB, Heath EM. Induction of low-T3 syndrome in exercising women
occurs at a threshold of energy availability. American Journal of
Physiology 1994; 350: R817-R823.

Jeff Johnson, MS
Performance Fitness & Nutrition

:cool: TJ :cool: