The causal connection between food security and weight status—to the extent that there is one—needs to operate through some mechanism, said Mark Nord, a sociologist at the Economic Research Service at the U.S. Department of Agriculture (USDA). This mechanism can be exceedingly complex. It can include, at a minimum, diet and health knowledge, nutrition motivation, cooking and food storage facilities, the physical ability to prepare food, physical activity, stress, genetics, and the inability to absorb and utilize nutrients because of some diseases (e.g., diarrheal disease) that interfere with nutrient incorporation into the body. Given these many factors, linking food security to weight status can be “almost a Herculean task,” said Nord.
Nord suggested keeping these questions in mind when using food security measurements:
Who is the measure describing—household, individual, which adult(s) or child?
What levels of food insecurity exist—marginal, low, or very low food security?
What time period does a measure cover—a year, a month, or persistent?
What is the expected theoretical relationship between a measure and a specific outcome?
As described in Chapter 2, many researchers measure food security through an 18-item questionnaire that is used to derive both an adult food security scale and a child food security scale (Hamilton et al., 1997). For almost all research purposes, including research on children’s weight status, Nord recommended using the adult scale. The children’s food security scale depends, to a considerable extent, on the oldest child in the household, and researchers typically do not know which child is the oldest. “Usually, the adult food security scale is what you want.”
Food security can be divided into four categories: high food security, marginal food security, low food security, and very low food security. Most people include marginal food secure with low and very low food security. This may be appropriate because, on many outcomes, households with marginal food security are more like those with low food security than