Calories - how many calories should I eat per day and why so few ;-)

When I have asked some people if they knew how many calories per day they needed, I have often heard “I don’t know, about 2000?”. I wasn’t surprised as this figure is used when recommended daily intake of nutrients is calculated and then included on food labels. But is the 2000 kcal correct amount for each of us? We are all different: some of us are woman, some man, some of us are very active, some have a very sedentary lifestyle and that is why each of us needs a different amount of a daily calories intake.

Estimating how many calories per day we need is fairly simple; but before we move to the calculation, we should understand what we need the calories for:

• Basal metabolism – energy needed for our body to perform basic functions (e.g. breathing, heart beating, maintaining the body temperature). As much as 60-80% of total calories are used by our bodies on basal metabolism - I was very surprised when I learnt it. But I was even more surprised when I found out that a slim person resting will burn more calories than an obese one because muscles need more energy than fat does. To calculate your basal metabolism you have to multiply your weight in kg by 22, if you are a woman or by 24.2 if you are a man.

• Physical activity – energy needed for being active depends on our lifestyle

     * Sedentary (less than 2 hours of mild activity (slow movement/standing) per day) - 30% of basal          metabolism calories,

      * Average (2-4h of mild activity per day) - 50% of basal metabolism calories,

      * Active (more than 4 hours of activity per day) -75% of basal metabolism.

• Dietary thermogenesis – energy needed to eat and digest food as well as to absorb nutrients. It amounts to 10% of total calories for basal metabolism and physical activity.
• Other factors like our height, health, muscles can influence the calories we daily require by +/-10%.

Let’s take an example of a woman weighing 65kg, leading an averagely active lifestyle:

Basal metabolism                                          65*22=   1.430 kcal

Activity calories - average lifestyle           1.430*50%=       715 kcal

Dietary thermogenesis                 (1.430+715)*10%=      214 kcal

Total                                                                          2.359 kcal

Other factors                                 2.359*(+/-10%)= +/- 236 kcal

so her daily calorie intake should fall between 2.123 kcal and 2.595 kcal.

If maths has never been your strongest subject ;-) or if you would like to find out more about recommended intake of nutrients for you, please take a shortcut and check this link.