Controlling
Human Energy Intake
The average woman has a basal metabolic rate (or resting
metabolic rate) of 6000 kilojoules (which is about 1400 kilocalories
(diet books and magazines often just call them Calories') a day. This
means that just staying in bed all day and dozing you would need about
6000 kJ energy to maintain your body weight and allow your body to function
normally (breathing etc.).
Everything you do from the minute you sit up in bed
in the morning to the last thing you do before you tuck yourself up
in the evening is classed as activity.
Activities cause your body to convert the energy that you have taken
in by eating and drinking into the type of energy you need for the activity....
CHEMICAL ENERGY (food) into HEAT ENERGY (body heat) and SOUND ENERGY
(speech etc.) + KINETIC (MOVEMENT) ENERGY (movement)
Below is a list of activities and the energy consumption associated
with them per hour.-
|
ACTIVITY
|
ENERGY TRANSFERED (kJ) for each
hour of exercise
|
|
Badminton
|
1250
|
|
Cycling (easy pace)
Cycling (strenuously)
|
1250
2500
|
|
Dancing (ballroom)
Dancing (disco)
|
1250
1800
|
|
Golf
|
1000
|
|
Ice Skating
|
1250
|
|
Jogging
|
1500
|
|
Roller-skating
|
750
|
|
Rock climbing
and hill walking
|
1500
|
|
Rowing (lazily)
Rowing (race-style)
|
1000
2500
|
|
Running
|
2500
|
|
Sailing
|
1000
|
|
Skipping
|
2500
|
|
Skiing
|
1250
|
|
Squash
|
2500
|
|
Swimming (gentle strokes)
Swimming (strenuously)
|
1250
2500
|
|
Table Tennis
Tennis
|
750
1000
|
|
Walking (strolling)
Walking (briskly)
|
500
1500
|
|
Yoga
|
750
|
The amount of food that you can eat without putting on weight depends
on your metabolic rate (the above figure is an average one !) and your
activity level. Any extra energy intake will be converted to stored
energy (fat !!) whereas any shortfall in energy intake will deplete
your store and cause you to lose weight. Anorexics continually partake
of less food that the body needs to function properly and may eventually
die because of this. Overweight people consume more food than their
current energy output requires. This is why people often put on weight
when they leave schooland no longer enjoy (or endure!) P.E. lessons.
The amount of energy you get from food depends on its
type and how much of it you have. If you eat two apples you will have
consumed twice the number of kilojoules than if you had eaten only one.
The way food is cooked affects its energy value. Fried
foods absorb some of the oil of fat they are cooked in and this affects
its total energy value on eating (see potatoes in the list below).
To work out your energy consumption for a day you would
need to carefully weigh all of the foods you eat and to work out how much
your energy intake is. A 'calorie controlled diet' is a means of reducing
weight by reducing food intake by carefully monitoring how much is eaten.
It is the safest and best way to diet as you can ensure that you have
a sensible balance of nutrients and variety of intake - you just learn
moderation in portion size!
|
FOODSTUFF
|
ENERGY CONTENT (kJ per I00g)
|
|
Apple (an apple is approx. l00g)
|
170
|
|
Bicuits (One biscuit is approx
l0g)
|
1900
|
|
Bread (toasted) (1 slice is approx.
40g)
Bread (white)
Bread (wholemeal)
|
1260
960
920
|
|
Butter (Bread requires about
8g butter per slice)
|
3360
|
|
Coffee (without sugar or milk)
|
negligible
|
|
Cucumber
|
40
|
|
Grapefruit
(a grapefruit is approx. 280g)
|
45
|
|
Ham (boiled)
|
670
|
|
Lettuce
|
50
|
|
Mars Bar (75g)
|
1860
|
|
Milk (skimmed)(1 litre milk has
a mass of l000g)
Milk (semi-skimmed)
Milk (whole)
|
140
220
270
|
|
Oat Bran Flakes
|
1500
|
|
Peas (frozen)
|
300
|
|
Potatoes (boiled)
Potatoes (chipped - trench fries)
|
340
1060
|
|
Steak (rump, grilled)
|
980
|
|
Tea (without sugar or milk)
|
negligible
|
|
Tomato (Fresh)
|
65
|
|
Water
|
nil
|
|
Wine (white medium dry)
|
315
|
|
Yoghurt (one pot - 125 g)
Yoghurt (diet)
|
340
200
|
Try this question on energy intake
and dieting.
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