Part D. Chapter 3: Individual Diet and Physical Activity Behavior Change
The majority of Americans consume meals outside of the home one or more times per week (see Part D. Chapter 1: Food and Nutrient Intakes, and Health: Current Status and Trends). The 2010 DGAC concluded that “strong and consistent evidence indicates that children and adults who eat fast food are at increased risk of weight gain, overweight, and obesity”.2 With this relationship as a foundation, the 2015 DGAC updated and expanded the review of the “eating out” topic. Specifically, the “fast food” category was broadened to capture other types of eating out venues (e.g., quick serve, casual, formal restaurants, and grocery store take-out). Terminology used to define the exposure was modified from “eating out,” to the broader term “eating out and/or take away meals” to reflect the inclusion of meals eaten out at a broader array of restaurant venues as well as takeout or ready-to-eat foods or meals purchased and consumed either away from or in the home. The population of interest remained healthy individuals ages 2 years and older.
Question 1: What is the relationship between eating out and/or take away meals and body weight in children and adults?
Source of evidence: Update to 2010 DGACs NEL systematic review
Among adults, moderate evidence from prospective cohort studies in populations ages 40 years or younger at baseline indicates higher frequency of fast food consumption is associated with higher body weight, body mass index (BMI), and risk for obesity. DGAC Grade: Moderate
Among children, limited evidence from prospective cohort studies in populations ages 8 to 16 years at baseline suggests that higher frequency of fast food consumption is associated with increased adiposity, BMI z-score, or risk of obesity during childhood, adolescence, and during the transition from adolescence into adulthood. DGAC Grade: Limited
Insufficient evidence is available to assess the relationship between frequency of other types of restaurant and takeout meals and body weight outcomes in children and adults. DGAC Grade: Grade Not assignable
Given that one-third of calories are consumed outside of the home (see Part D. Chapter 1: Food and Nutrient Intakes, and Health: Current Status and Trends), individuals should limit the frequency of eating at fast-food establishments. When eating out, one should choose healthy foods and beverages within their calorie needs to avoid increases in body weight.
Review of the Evidence
Fifteen prospective studies examined the relationship between eating out and/or take away meals and measures of body weight in adults and children.15-29 Eleven studies in the United States 16-18, 20-23, 25-28 and four international studies (one each from Canada, the United Kingdom, Australia, and Spain)15, 19, 24, 29 were reviewed. Men and women and boys and girls were well represented and the majority of studies within the United States included diverse populations.
In children, seven prospective cohort studies19, 21, 22, 24, 27-29 examined the relationship between frequency of fast-food meals, or consumption of other types of meals and anthropometric outcomes and, overall, found mixed results. Six studies examined fast-food meals19, 21, 22, 24, 28, 29: three studies19, 28, 29 indicated increased fast food intake, particularly more than twice per week, was associated with increased risk of obesity, BMI/BMI z-score or body fat, two22, 24 found no association, and one21 found no association in boys and a negative association in girls. Two studies looked at a variety of non-fast-food meals away from home, using varying definitions of food establishments and meal types and reported mixed findings for a relationship with weight-related outcomes.27, 28
In adolescents transitioning to adulthood, one study found high baseline frequency of fast food intake was associated with increased BMI z-scores at 5-year follow-up.25 In adults, evidence consistently demonstrated a relationship between higher frequency of fast-food meal consumption and body weight outcomes. Five prospective cohort studies (three cohorts) reported a higher frequency of intake of meals from fast food locations, or intake exceeding once per week, was associated with higher weight gain, BMI, and risk of obesity.17, 18, 20, 23, 26 A “moderate” grade was assigned (as opposed to the “strong” grade assigned by the 2010 DGAC) because the evidence based was small (five studies focused on fast food, three from the same cohort), all of which were prospective cohort studies; few studies controlled for energy intake and no study reported actual food consumed; and the method of measurement of “eating out” varied among studies. Evidence related to the association between frequency of meals from other types of restaurants and intake of all takeout meals and weight is limited, but indicates traditional restaurant meal frequency may not be associated with weight outcomes.17, 18 Two studies15, 16 examined total meals away from home or meal types eaten away from home, which came from both fast food and restaurant locations, and reported frequency was associated with increased body weight outcomes for most meal types. Two studies from the same cohort found no significant relationship between frequency of meals from restaurants (non-fast-food establishments), and weight-related outcomes.
For additional details on this body of evidence, visit: http://NEL.gov/topic.cfm?cat=3371