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How many calories will feed one billion hungry persons?

As we have already discussed, the hungry of the world are not starving to death. If they were, their situation would be famine, not hunger. So they have enough kilocalories to survive, but not enough for good health. (What most people call ‘calories’ is technically called ‘kilocalories’, abbreviated as ‘kcal’.) Before we get into the nitty-gritty of figuring out which macronutrients they need, in which quantities, let’s consider the overall question of the number of kcal needed per person — per day and per year. But since hunger afflicts hundreds of millions of persons, we also need a convenient way to characterize the total kcal needed by millions of persons.

The number of calories needed per person per day varies greatly, depending on age, gender, level of activity, and many other factors. In developed nations, a sedentary adult woman will need about 1800 kcal/day, and a sedentary adult man will need about 2200 kcal/day. The average (2000 kcal/day) is the figure used in nutrition labels in the United States. However, many persons in the developing world need considerably more calories. They have manual labor occupations. They travel mainly by walking. They do not have many of the modern conveniences of daily living, and so they must expend more energy than their developed-world counterparts.

The FAO uses 1800 kcal as the dividing line between enough calories, and not enough, for the purpose of identifying the hungry of the world. But what we are looking for is not the minimum kcal for survival. Instead, we want a number to use as a target, as an ideal number of kcal/day to ensure that people are well-fed. Of course, each person decides for themselves how much food, and which types of food, they eat. We are simply looking for a good number to use that will ensure they have ample food energy available.

In my forthcoming book, Hunger Math: world hunger by the numbers, I use 2740 kcal/day as the target number. The long explanation for this figure is found in the book. To summarize: that number of kcal/day is approximately the average for the most physically active adult men and women. It is more than sufficient to meet the needs of the majority of persons in the human race. Some individuals will need more calories, such as athletes or persons doing arduous manual labor on a daily basis. But for most persons, 2740 kcal/day is more than enough; they will be well-fed, and have a surplus of food available to them.

The number 2740 was also chosen because it is about one million kcal/year. This allows us to characterize the dietary energy needs of large populations very simply. One million kcal (per person per year) is 10 to the 6th power (1.0E+6). One million persons is also 10 to the 6th power. How many kcal/year do one million persons need? 10 to the 12th power (1.0E+12). How many kcal/year do one billion persons need? 10 to the 15th power (1.0E+15). The value of 2740 kcal per person per day allows us to easily characterize the food energy needs of large populations.

If about one billion person are chronically undernourished (i.e. hungry), do we need to provide 1.0E+15 kcal/year to end world hunger? No. The hungry have some food, and generally have enough kcal to survive. So we only need to provide a fraction of that number of kcal/year to end world hunger. (More on this topic in later posts.)

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