IN 1995, DIETZ1 published a case study in Pediatrics describing an obese 7-year-old African American girl whose family often ran out of money for food. He introduced the case study by stating, "Both hunger and obesity occur with an increased frequency among poorer populations in the United States. Because obesity connotes excessive energy intake, and hunger reflects an inadequate food supply, the increased prevalence of obesity and hunger in the same population seems paradoxical."1(p766) Dietz described the family's situation, in which the first welfare check of the month was spent on rent, leaving no money for food until the second check arrived. Meanwhile, the mother fed the child high-fat foods to assuage her hunger during these periods. Dietz wondered, "does hunger cause obesity?"
Dietz1 used the term hunger in his case study, but the phenomenon he described may be closer to the term food insecurity. The US Department of Agriculture defines food insecurity as "limited or uncertain availability of nutritionally adequate and safe foods or limited or uncertain ability to acquire acceptable food in socially acceptable ways."2(piii)3 Hunger is "the uneasy or painful sensation caused by a lack of food" or "the recurrent and involuntary lack of access to food."2(piii)3 The distinction between food insecurity and hunger is one of severity. A family will be categorized as "food insecure" if members are habitually concerned about their food situation or if an adult in the family occasionally goes without food (eg, skips meals). A family will be categorized as "moderately hungry" if an adult in the family goes without food or a child is cutting the size of his or her meals or "not eating enough," but will not be categorized as "severely hungry" unless an adult in the family goes without food for a whole day or a child in the family ever goes without food (skips meals). The US Department of Agriculture estimated that 12% of US households were food insecure, 3.3% were moderately hungry, and 0.8% were severely hungry in 1995.2
Another term, food insufficiency, was used by the Third National Health and Nutrition Examination Survey (NHANES III) and is the focus of this article. Food insufficiency was defined as living in a family that "sometimes or often did not get enough food to eat." Through cognitive testing of questionnaire items and comparisons of survey respondents' responses to food-insecurity, hunger, and food-insufficiency questions, it was determined that the NHANES III concept of food insufficiency is more severe than the concept of food insecurity, not as severe as hunger, and closer to the phenomenon of hunger than food insecurity.4- 10 Results from NHANES III found that 4.1% of the population was food insufficient between 1988 and 1994.
There is some evidence that food insecurity, but not hunger, the more severe form of food deprivation, is associated with obesity in adult women. In a sample of rural white Upstate New York women, the prevalence of obesity was significantly higher in food-insecure women than in food-secure women, but the prevalence among hungry women was similar to the prevalence among the food secure.11,12 Similarly, in an analysis of national data,13 food-insecure women, but not men, were more likely to be overweight than were food-secure women. However, in another analysis of national data,14 food-insufficient diabetic adults were twice as likely to be obese as were food-sufficient diabetic adults. In the only study15 on this topic conducted with children, to our knowledge, hungry, but not food-insecure, Mexican American preschool-aged children were significantly less likely to be overweight than food-secure children.
Several mechanisms have been proposed by which food insecurity could cause obesity. First, food-insecure individuals may be overweight because they can only afford to consume cheaper foods, which tend to be energy (calorie) dense and could result in the person consuming excessive energy and gaining weight.16- 19 Second, periods without enough food could cause individuals to overeat when there is enough food, resulting in increased energy intake overall, which would then cause a gain in weight.20- 27 Third, fluctuations in eating habits could result in the body becoming a more efficient user of energy, meaning that the individual could increase in weight without eating more calories; these fluctuations may not cause lasting changes in resting energy expenditure.28- 33
With this background in mind, we used data from NHANES III to investigate whether there is an association between family income and overweight, and between food insufficiency and overweight, in US children. Specifically, we answer 2 questions: (1) Is there a paradox? That is, does an increased prevalence of food insufficiency and overweight coexist in the population of US children living in families with low income? (2) Is food insufficiency independently associated with overweight, controlling for known confounders?
We present results from our analyses, and discuss design and data requirements for further research that could effectively examine this issue.