Sidney University. Australia: Dietary guidelines broadly recommend a daily intake of 10,000
kilojoules (2,400 calories) for men and 8,000 kilojoules (1,900
calories) for women. But what do these figures mean in the context of
the number of kilojoules or calories you personally need to consume to
attain and maintain a healthy body weight?
I'm going to stick with
kilojoules in this article because kilojoules - not calories - are the
metric unit for measuring energy, just as kilograms - not pounds - are
the metric unit for measuring body weight.
Daily kilojoule
requirements are based on many variables, and no two people are the same
across all of these parameters. It makes sense then that if we all
followed the same prescriptions for kilojoule intake, some of us would
gain weight while others might lose some. That's because any excess or
deficit between the number of kilojoules you consume and the number your
body uses results in weight gain or loss.
So how can you know what you need to maintain your energy balance?
There
are two options: the mathematical approach, which requires kilojoule
counting, and the instinctive approach, which involves "listening" to
your body (my personal preference).
Both approaches take some trial and error.
The mathematical approach
One
way to estimate how many kilojoules you need is to use an online
calculator that takes into account major factors regulating energy
requirements. These include your sex, weight, age and activity levels.
Some calculators also take height into account.
Such calculators
are based on prediction equations that estimate true energy requirements
- as measured in a laboratory - from readily available parameters.
While
some prediction equations may be slightly better than others, none of
them can tell you exactly how many kilojoules you need to consume to
maintain your weight. That's because no prediction equation can take
your genetic make-up, which may impact how fast or slow you churn
through kilojoules, into account.
Nor can they account for things
like whether you have more or less lean mass or fat on your body than
the average adult. Or that you may have spent the last few months on a
weight-reducing diet that has dropped the amount of energy you need to
maintain your weight by a few thousand kilojoules per day.
Despite
these limitations, once you have a ballpark figure of your energy
requirements, you can roughly work out how much you need to eat and
drink based on the kilojoule content of the foods and beverages you
consume.
For this you will need a comprehensive kilojoule counter
(I recommend CalorieKing, which has extensive data bases for Australia
and the United States) and a way to track your food and beverage intake
throughout the day (MyFitnessPal comes highly recommended). Numerous
other programs and apps are available for both.
The instinctive approach
We
also have the ability to maintain a healthy body weight without any
regard for kilojoule counting; the human body is endowed with a
remarkable system that enables us to attain and maintain an optimum
weight instinctively.
This system works by controlling your
appetite. When your body needs more kilojoules, you may feel hungrier
more often. And you may need to eat and drink a greater number of
kilojoules in order to feel satisfied.
When your body needs fewer
kilojoules, you may not feel hungry enough to eat all the meals and
snacks you normally eat in a day. When you do eat, it may take much less
than usual to satisfy your hunger.
Provided you heed your body's
appetite signals by eating when you are hungry - and only when you are
hungry - and eating enough to feel satisfied but not too full, then you
will be able to attain and maintain an optimum body weight.
Sounds
simple, doesn't it? It is when you eat a diet of foods that are close
to the form they appear in nature - that is, food that's minimally
processed.
Processed foods, which have many added ingredients such
as fat and sugar to make them palatable, make it harder for the body's
automatic weight-management system to do its job. That's because diets
high in fat, or high in fat and sugar, change the balance of natural
chemicals in the brain that control this system.
Using trial and error to get there
Regardless
of how you estimate the amount you need to eat, the current obesogenic
environment prevailing in most countries, which pushes us to gain
weight, means you will need to use some trial and error to determine
exactly how much to eat.
If you are gaining weight, or you find
your clothes are getting tighter, then you're consuming more kilojoules
than your body needs, period.
To prevent further weight gain, you
need either to cut your energy intake or to increase the number of
kilojoules you burn via physical activity - or both. Do this by becoming
mindful of the kilojoule content of the foods and drinks you consume.
Drinks are particularly important, especially alcohol, because they
sneak into your day and may not be accounted for.
Or you need to
keep a written hunger-and-satiety diary to ensure you're eating only
when hungry and only until you feel satisfied. And that your food
choices are as close to natural as possible.
In today's obesogenic
world, attaining or maintaining a healthy body weight doesn't just
happen naturally for most people. It usually requires conscious
attentiveness to how much and what you're eating. The good news is that
you can do this using external signals such as kilojoule counting, or
via your body's own internal signals.
If you live in
the Sydney metropolitan area and would like to find out about
participating in weight-management trials involving mathematical or
instinctive approaches to eating, please e-mail tempo.diet@sydney.edu.au or click here for more information.