There have been a lot of arguments for the exact amount of calories we need each day. The truth is it depends on several factors such as age, height, weight, lifestyle, general and overall health habits. It's even been discovered that how you eat your food can affect how many calories get into your system. 

Quick facts on calorie intake:

• Recommended calorie intake depends on factors such as age, size, height, sex, lifestyle and overall general health.
• The longer you chew your food, the more calories your body retains.
• Recommended daily calorie intakes in the US are 2,700 for men and 2,200 for women.
• Eating a big breakfast could help with weight reduction and maintenance.
• When food is eaten may matter as much as what and how many calories are eaten.
• Average calorie consumption in industrialized nations and a growing number of emerging economies is higher than it used to be.

Recommended daily calories intakes vary across the globe. The National Health Service says the average male adult needs approximately 2,500 calories per day to keep his weight constant, while the average adult female needs 2,000. In the U.S., it's recommended that men eat 2,700 calories and 2,200 for women. But rather than measuring every last calorie you eat, it's a much better approach to focus on a healthy and well balanced diet and lifestyle. 

Timing is another important factor. A big breakfast helps bring your weight down if it contains approximately 700 calories. When we eat our food matters way more than we think. 

Portion control is simply the easiest thing you can do to start, but it is the one thing people have the most trouble with. 

Calories and kilocalories are slightly different. One kilocalorie is a 1,000 calories. A kilocalorie is the amount of energy required to raise the temperature of 1 kilogram of water from 15° to 16° Celsius (centigrade) at one atmosphere.A "small calorie" refers to the traditional scientific term of calorie, meaning one-thousandth of a kilocalorie.

How many calories should you eat per day?

The Harris-Benedict equation, also known as the Harris-Benedict principle, is used to estimate what a person's BMR (basal metabolic rate) and daily requirements are. The person's BMR total is multiplied by another number which represents their level of physical activity. The resulting number is that person'srecommended daily calorie intake in order to keep their body weight where it is.

How to calculate your BMR

• Male adults
  66.5 + (13.75 x kg body weight) + (5.003 x height in cm) - (6.755 x age) = BMR
  66 + ( 6.23 x pounds body weight) + ( 12.7 x height in inches ) - ( 6.76 x age) = BMR
• Female adults
  55.1 + (9.563 x kg body weight) + (1.850 x height in cm) - (4.676 x age) = BMR
  655 + (4.35 x kg body weight) + (4.7 x height in inches) - (4.7 x age) = BMR

Figure out your daily calorie requirement:

• Sedentary lifestyle - if you do very little or no exercise at all
  Your daily calorie requirement is BMR x 1.2.
• Slightly active lifestyle - light exercise between once and three times per week
  Your daily calorie requirement is BMR x 1.375.
• Moderately active lifestyle - if you do moderate exercise three to five days per week
  Your daily calorie requirement is BMR x 1.55.
• Active lifestyle - if you do intensive/heavy exercise six to seven times per week
  Your daily calorie requirement is BMR x 1.725.
• Very active lifestyle - if you do very heavy/intensive exercise twice a day (extra heavy workouts
  Your daily calorie requirement is BMR x 1.9.

For the human body to remain alive, it requires energy. Approximately 20% of the energy we use is for brain metabolism. The majority of the rest of the body's energy requirements are taken up for the basal metabolic requirements - the energy we need when in a resting state, for functions such as the circulation of the blood and breathing.