Calorie Intake Versus Calorie Expenditure
Controls Body Weight & Fat Percentage
What Determines Our Body Weight - up or
down
Energy Intake vs. Energy Expenditure
Calories-in vs. Calories-out
As a living, changing thing, our body can
gain or lose weight depending on circumstances. This process of weight
gain or weight loss is determined by the energy-intake / energy expenditure
equation - otherwise known as calories-in, calories-out.
Weight and Energy Intake
Energy in this case is measured in units
called calories. We take in energy by eating or drinking anything that
contains calories. If we eat a bagel containing 200 calories, our energy
intake is 200 calories.
Weight and Energy Expenditure
Energy expenditure is made up of three
things. 1) Our Basal Metabolic Rate (BMR). On average this accounts for
about 60 percent of all energy expenditure, and is the amount of energy
or calories our body consumes on basic body processes alone, without any
additional physical activities. BMR varies according to several factors,
especially the fat-muscle ratio of our body and the amount of exercise
we take, but on average, our basal metabolic rate burns about 11 calories
of energy per pound of body weight (women), or 12.2 calories per pound
of body weight (men). 2) Physical Activity. On average this accounts for
about 30 percent of energy expenditure. 3) Dietary Thermogenesis. This
is the energy or calories we burn as we eat and digest food. It accounts
for about 10 percent of the total energy we expend.
Weight - The Energy Intake vs. Energy
Expenditure Balance
Like a see-saw, if our energy (calorie)
intake balances our energy (calorie) expenditure, our weight remains stable.
If we take in more energy (calories) than we use up, we gain weight. If
we take in less energy (calories) than we burn, we lose weight. This is
the basic law of weight gain and weight loss.
Weight Gain and Energy Intake/ Expenditure
If, as above, we take in more energy (calories)
than we burn, this surplus energy (calories) is stored as body fat. Although
different foods are metabolised and processed in the body in different
ways, fat cells are the ultimate destination for all nutrients your body
does not need for immediate use.
Weight Loss and Energy Intake/ Expenditure
If, as above, we take in less energy (calories)
than we burn, our body re-converts some of it's stored body fat back into
energy. Over time, this leads to weight loss.
Weight - Hormones, Steroids and Environment
Obesity expert Jules Hirsch wrote in the
British Medical Journal: "The balance of food intake and energy expenditure
that maintains constant energy storage is determined by the metabolism
of muscle, liver, pancreas and intestine. The balance is regulated by
the adrenal and sex steroids as well as adipose tissue itself, which together
create a complex set of signals [which affect] energy dissipation and
food intake. Hovering over this complex system are potent psychosocial
and behavioral factors."
In other words, even though the relationship between energy intake and
energy expenditure is clearly marked, it is affected by a huge number
of bodily and mental processes.
Energy Intake/ Expenditure - A Useful
Guide to Weight Control
Although there are a number of complex
factors that influence the energy-intake vs. energy-expenditure equation,
no one seriously challenges the basic equation between calories-in and
calories-out. So if you want to lose fat and keep your weight under control,
aim to reduce your calorie-intake below your calorie expenditure. This
is best achieved by a combination of sensible diet and regular exercise.
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