GRAY MATTER
A Taste Test for Hunger
By ROBERT JENSEN and NOLAN MILLER
Published: July 9, 2011
There are a few possible explanations: unequal distribution of wealth, inefficient or indifferent governments and aid agencies, and recent increases in world food prices. While these factors may play a role, at least part of the answer may be much simpler: we are measuring hunger incorrectly.
Suppose you want to figure out if someone has enough to eat. The standard approach is to compare the number of calories eaten to the number needed, with “need” defined by a statistical average across a population. In effect, policy makers tell people whether they are hungry based on whether the amount of calories they take in conforms to some externally imposed standard.
Of course, very few people actually conform to a statistical average. So what if, instead, you looked not just at how many calories people consumed, but at the food they chose to eat?
The best way to do this, we’ve found, is to start with a baseline, namely the share of calories people get from the cheapest foods available to them: typically staples like rice, wheat or cassava. We call this the “staple calorie share.” We measure how many calories people get from these low-cost foods and how much they get from more expensive foods like meat. The greater the share of calories they receive from the former, the hungrier they are.
The rationale behind this approach is straightforward. We are all familiar with the unpleasant sensations associated with hunger. These are the body’s way of telling us that we need more calories. Once those needs are largely met, people will switch to more flavorful, but more expensive, foods.
Imagine you are a poor consumer in a developing country. You have very little money in your pocket, not enough to afford all the calories you need. And suppose you have only two foods to choose from, rice and meat. Rice is cheap and has a lot of calories, but you prefer the taste of meat. If you spent all your money on meat, you would get too few calories. You might do this every so often, but usually you would spend almost all of your money on rice; when faced with true hunger, taste is a luxury you can’t afford.
But suppose you had a bit more money. You would probably add some meat to your diet, because now you can afford to do so while still getting the calories you need. You might even like meat so much that you start to switch away from rice even if you haven’t quite met your complete calorie needs, as long as you aren’t too far below.
Now think about the two approaches to measuring hunger. Researchers taking the standard approach would add up all the calories in the rice and meat you ate and declare you hungry if that total was less than your caloric need, regardless of the choices you made.
In the staple-calorie-share approach, however, they would look at the first case and say that since you were choosing to get almost all of your calories from rice, you must not be getting enough to eat; otherwise you would have switched to meat. But looking at the second case, they would say that since you are now eating some meat, you must be getting enough or nearly enough calories; otherwise, discomfort would cause you to seek more calories via rice. Thus, the decline in the share of calories from rice reveals that the person has had enough to eat.
In principle, both approaches can tell you who is hungry and who is not. So, why look at staple calorie share?
With the standard approach, you need to know how many calories the person has taken in and how many the person needs. But that need varies widely based on age, sex, activity level and dozens of other factors. Though some of the factors affecting calorie needs are measurable, many are not.
Moreover, it’s hard to know how many calories a person is actually getting, since health factors, including the widespread incidence of diarrhea, often mean that only a fraction of calories eaten are absorbed by the body.
The staple-calorie-share approach eliminates both problems. Your choice of foods reveals whether you have enough calories. Staple-calorie-share “need” is less variable across people; though one person may need more calories than another, they will both begin to switch away from staple foods when their needs are met. And your body isn’t fooled by how many calories you put into your mouth; the physical sensation of hunger is regulated by the amount of calories you actually absorb.
The staple-calorie-share method can give us a radically different view of who is hungry and who is not. The standard approach reveals that in China, the fraction of people consuming fewer than 2,100 calories increased to 67 percent from 53 percent between 1991 and 2001. However, the fraction who appeared hungry, as measured by staple-calorie share (using a threshold of 80 percent of calories consumed through staples), declined to 32 percent from 49 percent.
Thus, instead of 150 million more hungry people in China, there were actually almost 200 million fewer. Rising incomes have indeed made people better off; however, they have used their increased purchasing power to buy better-tasting foods, and nonfood items, rather than to increase calories.
None of this is to say that hunger is not a critical issue: no matter how you measure it, hundreds of millions of people around the world aren’t getting enough to eat. But aid money is a scarce resource, and policy makers have to decide whether it is best spent on food aid or other forms of vital assistance, like health care. Adopting a more nuanced and accurate measurement of hunger would be a big help in making those lifesaving decisions.
