What are calories
Nutritionists measure the amount of heat produced by metabolising food in units called KILOCALORIES(kcal).
A kilocalorie is the amount of energy it takes to raise the temperature of 1 kilogram of water at sea level by 1 degree.
It can also be express as KILOJOULES - which is more scientifically accurate but Kcals has been adapted as the norm.
1 Kcal is equivalent to 4.18 Kj.
When you read that something, like a banana, has 105kcal -
it means that the banana produces 105 calories of heat(energy) that your body can use.
Calories do not depend on the amount of food but the nutrients they contain.
1 gram of Has this many calories
1 gram of carbohydrate has fewer calories than
1 gram of fat therefore that is why chocolate contains more calories than a potato.
What do we mean by Empty Calories?
All food provide calories, all calories provide energy but not all calories contain the nutrients we need such as Amino acids, fatty acids, fibre, vitamins and minerals so are nutritionally empty hence the term Empty Calories.
Sugar is a good example of an empty calories food.
It will give you energy from the calories but no nutrients.
It is good to point out the chemical that is sugar, is found in food which is nutritionally rich such as fruit. So in cases such as this any benefits of the rest of the nutritional content far outweigh the negative empty calories of the sugar.
So how do they actually measure those calories?
Nutritionist burn food in something called a BOMB CALORIMETER.
This is a box with 2 chambers, one inside the other. They weigh a sample of food placed into the inner chamber and then fill this chamber with oxygen and seal it.
The outer chamber is filled with a measured amount of cold water. The chamber containing the oxygen is then ignited by a heating element. There is a thermometer in the water and as the food burns the rise in the water temperature is recorded. So if the temperature rises by 1 degree for each kilogram of food burnt, the calorie value is 1
How many calories do you need?
Think of your intake as a bank,
every time you eat or drink something you make a deposit into your body bank and your body makes a withdrawal with activity.
So look at it in two parts
the energy you use at rest
the energy you use when physically active
It is about keeping everything in balance you need to take in enough to cover your withdrawals from your body bank.
The energy you use at rest-
RESTING ENERGY EXPENDITURE (REE)
or BASAL METABOLIC RATE (BMR)
We know activity such as HIIT classes increase the amount of energy you use at rest.
The scientific name for it is REE Resting Energy Expenditure Rate -
on the Body composition scales it is also known as your
BMR Basal Metabolic Rate
and this increases with your weight and other factors, but can account for up to 60-70% of your daily calorie usage.
There are lots of factors that can affect your REE.
The efficiency of your glands such as thyroid and pancreas,
(all glands that produce hormones which regulate the body)
Whether you are male or female also effects it with the production of testosterone in men or oestrogen & progesterone in women.
As a woman you will know this, your menstrual cycle effects your appetite.
At ovulation your appetite will be at its highest in sync with you REE rate which increases, hence some women develop cravings - the same as in pregnancy.
Men have it easier they don't have these hormones rushing around and don't feel the need to satisfy cravings as some women may have.
The energy you use when physically active
The second part - the withdraw - Is easy to understand and covers everything you do in a day from brushing your teeth through to a class.
So for weight loss or gain this "calorie in - versus calorie out has to balance"