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HUMAN
METABOLISM
AND THE CALORIE
CONUNDRUM
‘Energy in minus energy out’ is not as simple as
it may seem, with a host of factors affecting both
parts of the equation, writes dietitian and sports
nutritionist Brian St. Pierre.
aining and losing fat changes the
way your brain regulates your
body weight. To understand this,
let’s have a refresher on how human
metabolism actually works and explore what
that means for your clients, most of whom
are probably counting calories.
G
Energy balance
You need a certain amount of energy (in
the form of calories) to stay alive, as well
as to move around. You can get this energy
from food, or you can retrieve it from stored
energy, such as your fat tissue. If you
consume less energy than you expend, you
will lose weight – and if you do the opposite,
i.e. consume more energy than you expend,
you will gain weight.
In other words: Changes in bodily tissues
= Energy in - Energy out.
This relationship between ‘energy in’ and
‘energy out’ is called the Energy Balance
Equation, and it’s the most commonly
accepted model for calculating how much
weight one will lose or gain over time.
ssUnderstandably, people get very
frustrated and confused with the Energy
Balance Equation when the numbers don’t
seem to add up, or their results don’t match
their expectations. And it’s a fair frustration.
Most of the time, the numbers don’t add up.
Expectations versus reality
This mismatch between expectations
versus reality is not because the Energy
Balance Equation is wrong, or a myth.
Nobody’s body defies the laws of physics,
even though it seems like that sometimes.
It’s because the equation is more
complicated than it sounds.
Many factors affect the Energy Balance
Equation. What you do to ‘energy in’ affects
what happens to ‘energy out’ and vice
versa. The opposing sides aren’t mutually
exclusive.
‘Eat less, move more’ is a good start – but
that advice alone isn’t enough, because it
doesn’t take all of the complex, intersecting
factors and feedback loops into account.
Let’s take a look at some of these factors,
starting with the ‘energy in’ part of the
equation.
Energy in
‘Energy in’ is trickier than it first
sounds, for two main reasons:
Reason 1: Inaccurate nutrition
labelling
It might sound hard to believe,
but the number of calories in a
meal probably doesn’t match
the number of calories/kilojoules
on the labels or menu. The
way companies, and even the
government, come up with energy
(kilojoule/calorie) and nutrient
estimates is incredibly complex,
rather imprecise, and centuries-
old. As a result, the Nutrition
Information label that’s mandatory
THE QUICK READ
• The Energy Balance Equation of
‘Energy in - Energy out’ is commonly
used for calculating weight loss, or
gain, over time
• People’s frustrations at failing to lose
weight despite following the equation
is due in part to inaccurate nutrition
information labels, and in part to
variations in how much energy we
actually absorb and how much
energy we use
• The factors that affect absorption
include how processed the food is; how
the food has been prepared or cooked;
and our unique gut bacteria
• The amount of energy we use is affected
by four main factors of resting metabolic
rate; thermic effect of eating; physical
activity; and non-exercise activity
thermogenesis
• Altering any one of the variables causes
adjustments in other, seemingly
unrelated variables.
NETWORK AUTUMN 2019 | 19