Part D. Chapter 3: Individual Diet and Physical Activity Behavior Change
Individual behavior change lies at the inner core of the social-ecological model that forms the basis of the 2015 Dietary Guidelines for American Advisory Committee (DGAC) conceptual model (see Part B. Chapter 2: 2015 DGAC Themes and Recommendations: Integrating the Evidence). For this reason, it is crucial to identify the behavioral strategies that individuals living in the United States can follow to improve their healthy lifestyle behaviors as well as the key contextual factors that facilitate the ability of individuals to consume healthy diets.
In the past, American families seldom consumed food prepared outside their homes and, for the most part, consumed their meals as a family unit. However, these behaviors have changed dramatically in recent years. Today, 33 percent of calories are consumed outside the home and it is becoming more common for individuals to eat alone and to bring meals prepared outside into their homes (see Part D. Chapter 1: Food and Nutrient Intakes, and Health: Current Status and Trends). Eating away from home is associated with increased caloric intake and poorer dietary quality compared to eating at home.1 As recognized by the 2010 DGAC these major changes in eating behaviors can be expected to have a negative impact on the quality of the diets consumed and the risk of obesity among the U.S. population.2
Other individual lifestyle behaviors related to dietary intakes and obesity risk also have changed in recent decades. The U.S. population has become increasingly sedentary,3 with daily hours of screen time exposure becoming a serious public health concern due to its potential negative influence on dietary and weight outcomes. For example, it has been hypothesized that TV viewing time has a negative influence on dietary habits of individuals because of unhealthy snacking while watching TV and through exposure to advertisements of unhealthy food products.4 In turn, excess caloric intake coupled with sedentary time directly resulting from excessive TV may increase the risk of obesity. Suboptimal sleep patterns associated with todays busy lives also have been identified as a potential risk factor for poor dietary behaviors and body weight outcomes.5
In response to these trends, interest has grown in the potential of behavioral strategies that individuals can use to improve their dietary behaviors. Specifically, self-monitoring of diet, physical activity, and body weight has been identified as a potential key component of successful healthy lifestyle interventions.6 Diet self-monitoring may, in turn, be facilitated by the availability and use of menus displaying calorie labels and the Nutrition Facts label on packaged foods.
Recognizing the importance of these dietary and lifestyle behaviors to the health and well-being of the U.S. population, the DGAC reviewed recent evidence to address questions on the relationship between eating out, family shared meals, sedentary behavior, and diet and weight outcomes. The DGAC also sought to examine associations between sleep patterns, dietary intakes, and obesity risk. However, after conducting preliminary literature searches, the Committee determined sleep patterns was an emerging area with an insufficient body of evidence and did not include specific questions on this topic.
The DGAC also focused on identifying evidence that could provide individuals with tools to improve their dietary choices and body weight status. Specifically, the Committee reviewed recent evidence on the impact of diet and weight self-monitoring, and on use of food and menu labels on dietary intake and weight outcomes. The DGAC was interested in reviewing the evidence on the use of mobile health (m-health) technologies to improve dietary and weight outcomes, and after a preliminary review was conducted, determined that this, too, was an emerging area and that a full evidence review was premature. However, key m-health studies focused on self-monitoring were identified, and thus were reviewed as part of the body of evidence on self-monitoring. This chapter addresses sedentary behaviors, but not physical activity behaviors in general because these are addressed in Part D. Chapter 7: Physical Activity.
Consistent with the DGAC conceptual model presented in Part B. Chapter 1: Introduction, this chapter also addresses major contextual factors that influence the ability of individuals to implement healthy dietary and other lifestyles, including the prevention of sedentary behaviors. The Committee focused on the association between diet, body weight, and chronic disease outcomes and two contextual factors that are highly relevant in the United Stateshousehold food insecurity and acculturation.
Household food insecurity is defined as “access to enough food for an active, healthy life. It includes at a minimum (a) the ready availability of nutritionally adequate and safe foods, and (b) an assured ability to acquire acceptable foods in socially acceptable ways (e.g., without resorting to emergency food supplies, scavenging, stealing, or other coping strategies)”.7 Thus, household food insecurity is a condition that exists whenever the availability of nutritionally adequate and safe foods, or the ability to acquire acceptable foods in socially acceptable ways, is limited or uncertain.7 In 2013, 49.1 million people in the United States lived in food insecure households, and of these, 8.6 million are children.1 Household food insecurity is suggested to be an independent risk factor for poor physical and mental health outcomes across the lifespan.8, 9
The second contextual factor the DGAC addressedacculturationreflects that the United States continues to be a nation of immigrants.10, 11 Acculturation has been defined both as the “process by which immigrants adopt the attitudes, values, customs, beliefs, and behaviors of a new culture”,12 and as the “gradual exchange between immigrants original attitudes and behavior and those of the host culture”.13 Acculturation is relevant for individual dietary behaviors because evidence suggests that the healthy lifestyles with which immigrants arrive deteriorate as they integrate or assimilate into mainstream American culture.14 Moreover, evidence suggests that to be effective in helping immigrants retain their healthy lifestyles, nutrition education programs, including those that are a part of food assistance programs, must be tailored to their different levels of acculturation.14
Given the strong relevance of household food insecurity and acculturation as contextual factors influencing healthy lifestyles, the DGAC examined associations between them and diet, obesity risk, and whenever possible, corresponding chronic disease risk factors.