Per Person Per Day Food Requirement - The Easy Version

The mass taken in the following calculation is 50 kg per person. This is the average mass of population when taking into account the entire population including men, women and children. Mass of a grown up man is 75 kg on average, of a grown up woman is 62.5 kg.

40 calories per kg body-weight per day is for average work. Farming requires 50 calories and office work 30. At the two extreme ends, an athlete requires 60 and a person in comma 20.

Food has macro nutrients, micro nutrients, fiber, water. This is the water present inside the food itself i.e. not the water drunk separately. Usually 10 to 20 percent of food by mass is fiber and an equal amount is water.

Per day per person, macro nutrients are consumed in grams, micro nutrients in micro or milli grams, fiber in grams, water in grams.

The three macro nutrients are carbohydrates, proteins, fats. The two micro nutrients are vitamins, minerals.

Calories come from macro nutrients only. Micro nutrients are used for repairing of body. Fiber is used for diluting the food so that it can be digested easily. Water is used for cleaning and cooling.

Even though all macro nutrients provide energy, not all of the macro nutrients are used for the actual physical work of body. Only energy from carbohydrates is used for actual physical work. Energy from proteins is used only if energy from carbohydrates is not enough; usually proteins are used for providing the stuff that repairs the body. Fats are used as an energy reserve and to make the fats layer below the skin, this layer kills most of the germs and viruses that tries to penetrate the body and keep body warm. Vitamins act as catalysts. Nutrients are also used as stuff to repair the body along with proteins.

In spite of energy used for physical work comes from carbohydrates and not from proteins or fats, since they are also needed therefore in calculation of food requirements they are also calculated, so the following calculation is valid and highly applicable.

One calorie is 4.2 joules. One Calorie (with capital c) is 1000 calories. In food calculations calories is always Calories. Therefore, in this article wherever (other than this paragraph) calorie is written with small c or capital c it means the larger unit, the Calorie. One calorie is the amount of energy needed to raise temperature of 1 gram of water 1 degree Celsius. One Calorie is the amount of energy needed to raise temperature of 1 kg of water 1 degree Celsius.

Carbohydrates would be referred as CH, proteins as P, fats as F in the charts below.

Ideal Proportion of Calories from Macro Sources:

CH: 56% = 1120 calories = 280 grams (4.0 calories / gram).
P: 14% = 280 calories = 70 grams (4.0 calories / gram).
F: 30% = 600 calories = 65 grams (9.2 calories / gram).

Total: 100% = 2000 calories

Item   Grams    CH      P       F       Calories  Rs/Kg    Rs 

Fruit      250  31.25   -       -       125         90      22.50
Milk       250  12.20   8.30    9.10    167         66      16.50
Wheat      125  83.33  15.00    3.44    425         38       4.75
Oats        63  33.50   5.00    -       154         68       4.25  
Rice        63  43.75   6.25    2.72    225        130       8.13
Pulses      63  31.25  15.63    4.08    225        100       6.25
Chicken     16  -       3.91    0.20     18        250       3.91
Fish        16  -       2.81    -        11        250       3.91
Mutton      16  -       3.91    0.20     18        400       6.25
Beef        16  -      12.50    -        50        300       4.69
Oil         31  -      -       31.25    288        130       4.16
Sugar        8   7.81  -       -         31        130       1.01
Honey        8   6.25  -       -         25       1040       8.13
Butter       8  -      -        6.25     58        350       2.73
Dry Fruits   8  -       1.56    3.90     42       1040       8.13 
Spices      31  15.63   6.25    3.13    116        100       3.13

Total      969  265     81     64      1976                104.27
                 54%    16%    30%

All minerals needed by body can be achieved by above mentioned honey. Vitamins can also be achieved from the above mentioned items. Fiber and water are present in all of the above items except oil and sugar. Fiber and water are not present in oil and sugar because both of them have 100% place occupied by one or more macro nutrients.

Amount:

The amount calculated above is Rs. 104.265. It should be noted that the calculation in case of fruits and meat is for the actual thing, not for the shells and seeds and bones etc. It should be noted that the food purchased from market has about one third of such stuff. Therefore in case of fruits an addition of Rs. 11.25 must be taken into account because fruits must be bought 375 grams instead of 250 grams. In case of meat the majority of non-eaten stuff is bones and there is some fat still present when the food reaches the table. We can take a ballpark figure of one third there too. Total amount estimated for meat is Rs. 18.76 therefore Rs. 9.38 must be added because instead of 62.5 grams 93.75 grams meat must be purchased. Total additions therefore is Rs. 11.25 + Rs. 9.38 = Rs. 20.63. The final amount therefore becomes Rs. 104.265 + Rs. 20.63 = Rs. 125.

Note: This article was written using prices in Pakistani rupees in Karachi as of 23rd Sep 2010.