Food insecurity is closely tied to socioeconomic status and is therefore discussed here even though it is arguably a modifiable factor. Several studies have identified a relationship between food insecurity, defined as “whenever the availability of nutritionally adequate and safe food or the ability to acquire acceptable foods in socially acceptable ways is limited or uncertain” (Anderson, 1990). These studies have shown a higher prevalence of overweight and obesity among women living in food-insecure households compared to women living in food secure households (Frongillo et al., 1997; Olson, 1999; Townsend et al., 2001; Adams et al., 2003; Basiotis and Lino, 2003; CDC, 2003; Crawford et al., 2004). The mechanisms mediating this association are not well understood. Reports in the literature addressing eating patterns support the idea that food deprivation can result in overeating (Olson and Strawderman, 2008). Polivy (1996) found that food restriction or deprivation, whether voluntary or involuntary, results in a variety of changes including the preoccupation with food and eating. It has also been suggested that food-insecure households tend to purchase caloriedense foods that are often high in fats and added sugars as an adaptative response to food insecurity (Drewnowski and Darmon, 2005). Corroborating this causal link, Wilde and Peterman (2006) examined the relationship between food insecurity and change in self-reported weight over 12 months in a national sample of nonpregnant women. They found that women in households that were marginally food secure were significantly more likely to gain 4.54 kg (10 pounds) or more in a year compared to women in food-secure households. In contrast, Jones and Frongillo (2007) found that although food insecurity without hunger was associated with risk for overweight/obesity, it was not associated with subsequent weight gain in women of all racial/ethnic groups.
Although food insecurity and obesity have been shown to be positively associated in women, little is known about the direction of causality between food insecurity and obesity. In a cohort of 622 healthy adult women from rural areas followed from early pregnancy until 2 years postpartum, Olson and Strawderman (2008) found that food insecurity in early pregnancy was not associated with increased risk of obesity at 2 years postpartum, suggesting that the causal direction of the relationship between food insecurity and obesity likely goes from obesity to food insecurity. Moreover, they found that women who were both obese and food insecure in early pregnancy were at greatest risk of major gestational and postpartum weight gain, suggesting that food insecurity may play a role in GWG (trends in food insecurity are shown in Chapter 2).