Energy requires to create movement. In my previous blogs I have discussed that it comes from carbohydrates, fats and protein.
The energy obtained from the sources is measured in calories.
A calorie represents the amount of heat produced when we burn the food.
A calorie is the energy required to raise 1 gram of water by 1 degrees Celsius. And a kilocalorie, is the energy required to raise 1 kilogram of water. It is recommended that female consumes approx 2000 kcal per day and male around 2.500.
A calorie is also an equivalent of 4.2 joules and kilocalorie, of 4.2 kilojoules.
Generally the product food label will state the number of calories per 100g and often another value to indicate the pack size.
Our metabolism
Metabolism is the term used for all the chemical processes that occur within the body. These processes include breaking down the body structures as well as the food we eat. The processes also involve rebuilding of the foods we eat so these can be used for reconstruction of cells.
The process of breaking down the foods is also called carbolic reaction. And the reconstruction of cells is called anabolic reactions. These can involve rebuilding of the body tissue.
Carbohydrates
Next to fats and protein, the energy is sourced from carbohydrates. These, can be divided into simple carbohydrates and complex carbohydrates. Simple carbohydrates, such as glucose can be broken down quickly in the body and used as energy. Complex carbohydrates (for example rice, break or potatoes) take longer to be broken down and provide energy at a slower rate.
All carbohydrates are broken down in the digestive system into glucose. If there is excess glucose it groups with other molecules in our bodies and produce glycogen. The glycogen is stored in our muscles and liver ready to be used. It is than broken down to produce energy, carbon dioxide and water.
Over 50% of the diet should come from carbohydrates.
Fats
Fat is necessary in our bodies to absorb solute vitamins. It also helps to maintain body temperature and aids development and growth. Fats also produce hormone and insulate the nervous system. Approx. 30% of diet should come from fats.
Saturated fat is generally solid in room temperature and generally comes from animal sources. We find it in butter, cheese, margarine, whole milk, but also cakes, pastries, chocolates and biscuits. 10% of the diet should be made of saturated fats.
Unsaturated fats is usually liquid in room temperature. Mainly, it comes from vegetable sources. These can be found in nuts, olives, avocados and olive oil, but other sources also include sunflower or seed oil. Fats from these sources lower the risks of strokes, heart disease and other health problems. 20% of our diet should be made of unsaturated fats.
Protein
Protein are essential for growth and repair. These are vital for body's metabolism. Proteins make up skin and bones and provide structural support. Proteins can be found in fish, meat poultry, cheese, eggs, soya and nuts. 15% of our diet should be made of proteins.
Energy systems in our body
There are three main energy systems in our bodies: ATP-PC (down as the 'energy currency of our movement), the lactic acid system and the aerobic system.
ATP is the molecule stored within the muscle. When it reads down it releases energy that the muscle can use for contraction. If exercise intensity is high and fast the body uses the ATP-PC system. This is because the fuel available in this system is readily available within the muscle. It therefore meets the immediate need for an activity. This system also doesn't use oxygen to create energy. The main source of these is generally meat.
Lactic acid system is built from carbohydrates. The body uses glucose and glycogen to create energy. It is used with moderate-high exercise and releases lactic acid.
The aerobic system uses carbohydrates and fats. It is used with low intensity exercise, for example marathon.
The majority of exercises will require all the different energy systems.
As an example during my run when warming up the intensity is low and the body has time to break down the fats to provide me with energy. Here, the aerobic system will be the dominant system.
When I start my run, the intensity increases and the ATP-PC system will be used. The lactic acid system will also continue to provide the energy for the duration of my run.
What affects the energy requirements?
Each person is different and has different energy requirements. It would depend on our age, gender, body composition and levels of activity.
A young child who is still growing will require higher amounts of calcium for bone growth than an adult. But a child will also need less calories. By the age of 50 our energy requirements are lower still. This is due to decrease in resting metabolic rate and decrease in physical activity.
Males generally require more energy due to their larger body size.
The level and intensity of physical activity will also affect the number of calories to maintain the energy balance. Someone who is training frequently would need a greater amount of carbohydrates to fuel the training sessions. Sometimes they may need even up to 5000-6000 kcal.
Body composition refers to the muscle tissue and fat we have in our bodies. Muscle tissue burn calories and the more lean muscle tissues we have, the more calories we will burn. This happens even when we rest.
Additionally, we we are exposing ourselves to a higher level of stress it can lower our BMR. Ilnesses and environmental temperature would also influence our metabolic functions.
Energy Balance
Energy Balance describes energy intake and expenditure. This means that it will account for number of calories we consume the energy release. The energy expenditure can be divided into: Physical activity levels - when we exercise (makes up to 15-30% of total energy expenditure), Basal metabolic Rate - when we rest (BMR that makes up to 60-70% of total energy expenditure) and Dietary thermogenesis - when we digest the foods we eat (makes up to 10-15% of total energy expenditure).
If the energy expenditure is greater than the energy intake weight loss will occur. If the energy intake is more than the expenditure weight gain will happen. If the energy intake is equal to energy expenditure the body weight will remain the same.
When we eat too much the body weight increases. The body stores the excess energy and fat. On the other hand when we eat too little, the body uses the reserves of fat to provide energy and therefore reducing our weight.
In the UK today, obesity is recognised problem in children and adults. The government is challenged with health-related issues and invest in providing healthy eating advice.
We can calculate the total daily energy requirements for us. There is many apps available on the market to help us to do so.
There is also many different methods for calculating energy intake. Commonly used food diaries are helpful with this task. One downside of these is that it is easy to forget to log some foods and therefore we often underestimate what we eat. Even though not entirely accurate, this methods can provide a very useful insights to help us maintaining a healthy weight. Reports confirm that if we are being ask to monitor our daily intake we generally reduce it for that reason.
Estimate your total daily energy requirements
One very useful method I have found to determine what calories intake I should have and the amount of exercise requires is to estimating BMR (Basal Metabolic Rate) and PAL (Physical activity Levels).
BMR will determine the number of calories I would burn if I stayed in bed all day.
PAL represents the number of calories needed to fuel each of individual physical activities.
As an example, a female of 36 years old with 65kg in weight with sedentary activity level.
BMR = (8.3 X 65) +846 = 1386 kcal/day
PAL = 1.2
Therefore, energy requirement BMR X PAL = 1386 X 1.2 = 1663 kcal/day calorie requirements.
We can also determine PAL more accurately by knowing the calories burned during 1 hour of certain activity per body weight.
24-hour recall
24-hour recall is a method of writing down all the foods and drinks from the previous 24 hours. This relies on accurate memory and making a good estimation of portion sizes.
Food frequency questionnaire
Food frequency questionnaire consists of a list of foods and options to select how often a food type is consumed i.e per day, week or month. This helps to built an overall picture of dietary habits. However, lengthy and time consuming process this can give a good insight of how our diet should change.
Accurate weighing and measuring of foods is however needed for detailed insights.
Apps can be very useful here. They have recently become very popular to keep track and measure energy intake as well as expenditure. Apps also provide summary data reports and can be synchronised with other health apps for even better energy management.
Gas analysis
One way of monitoring energy expenditure involves expensive equipment which measures the amount of oxygen breathed in, against the carbon dioxide breathed out. This method is rather expensive. There are other equipment, however, perhaps less accurate, but much cheaper. These include: activity monitors, pedometers (measuring the number of steps we take and number of calories burned, distance, walking time and speed), heart rate monitors (used on their own or as part of fitness trackers).
We must remember, however that these apps and trackers are only estimations. There is many variables which could affect the information, such as body composition, sleep quality or current fitness levels.
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