Table 1.

Characteristics of the studies included in the systematic review.

Reference	Study Design	Sample Size	Age	Intervention Description	Diet Assessment	Results
Murphy et al., 2011 [39]	Cluster, randomized controlled trial 1 year. PSFBI	4472	9–11 years	Free school breakfasts containing milk-based drinks or products, cereal (not sugar coated), fruit and breads compared with their usual breakfasts.	Dietary recall questionnaire.Questionnaire about child’s dietary behavior.	Higher consumption of healthy food items in intervention group than control group. Intervention group had more positive attitudes towards breakfast eating than control group.
Williamson et al., 2012 [46]	Cluster, randomized 3-arm controlled trial. 3 academic years. LA Health	2021	7–12 years	(1)Primary Prevention (PP): school environment modification including changes in cafeteria food service and physical education program. (2)Primary + Secondary Prevention (PP + SP): added a classroom/Internet component. (3)Control (C).	Digital photography of food selections and food intake.	No differences between PP + SP and PP and C were found for changes in BMI, body fat, food intake, physical activity or sedentary behavior. Both intervention groups combined (PP + (PP + SP)), were associated with a decreased in body fat and dietary fat intake in comparison to control group.
Brauchla et al., 2013 [41]	Cluster, randomized controlled trial. 2 months.	81	7–11 years	Two high-fiber snacks per day total of 10–12 g of dietary fiber compared with their usual snacks.	24 h dietary recalls via telephone. 8-question Child Regularity Questionnaire. Snack frequency questionnaire.	No differences were observed in terms of energy content, macronutrients, fiber, food groups and punctuation of Regularity Questionnaire between both groups.
Andersen et al., 2014 [37]	Cluster-randomized, controlled, unblinded, cross-over trial. 3 months. OPUS School Meal	834	8–11 years	Free healthy school meals: mid-morning snack, an ad libitum hot lunch meal and afternoon snack compared with their usual packed lunches.	WebDASC: food record tool.	Higher intake of potatoes, fish, cheese, vegetables, eggs and drinks and a lower intake of bread and fats during intervention period compared to control period. Lower energy density of food and beverages during intervention period than in control period. No differences were observed in energy intake during intervention period compared to control period. Higher energy intake from protein (0.9%) and lower energy intake from fats (0.9%) in intervention period. Higher intake of vitamin D (42%) and iodine (11%) in intervention period.
Li et al., 2019 [47]	Parallel, two-arm, cluster-randomized controlled trial. 1 year. CHIRPY DRAGON	1641	6–7 years	In the intervention school the following components were carried out while controls schools continued with usual practice: Education workshops, healthy behavioral challenges and quizzes for families and children. Provision of school lunch Family friendly games at school and home. 1-h physical activity on campus every day.	Short form of SFFQ from University of Leeds. Day in Life Questionnaire.	Higher daily intake of fruit and vegetables and proportion of children consuming at least 5 daily portions of fruit and vegetables in intervention group than in control group. Lower weekly consumption of sugar-sweetened beverages and unhealthy snacks in intervention group compared to control group. Lower proportion of children with screen-based sedentary behavior and higher proportion of children engaging active sport in intervention group compared to control group. More favorable score in questionnaire of quality of life in intervention group than in control group. Decrease in BMI z-score and waist circumference in intervention group compared to control
Cohen et al., 2014 [42]	Randomized, controlled trial. 1 academic year CHANGE	432	6–12 years	Daily access to a food service offering healthier school breakfasts and lunches. Healthy habits acquisition curricula. Different components to promote healthy lifestyle changes for parents and community encouraged during and after the school day.	Block Food Screener	Higher consumption of vegetables and fruits and vegetables combined in intervention schools compared to control schools. No difference was observed in fruit, legume, whole grain or dairy intake. Lower glycemic index of the diet in intervention schools compared to control schools.
Cullen et al., 2015 [43]	Randomized, controlled trial. 6 months.	1876	5–14 years	Intervention and control schools served the same menu, with the difference that intervention group could select one fruit and two vegetables servings per day and control group could only select a total of two servings of fruits and/or vegetables.	Direct observation in the cafeterias during lunch periods.	In elementary intervention schools, increase in the consumption of total vegetables, starchy vegetables and other vegetables and decrease in the consumption of calories juice, whole grains and protein foods compared to control schools. In intermediate intervention schools, increase in the consumption of fruit, total vegetables, starchy vegetables, legumes and decrease in the consumption of calories, total grains and whole grains compared to control schools.
Wolfenden et al., 2017 [48]	Randomized controlled trial. 1 year	57 schools (mean number of students: 256 in intervention group and 253 in control group)	5–12 years	Implementation of a healthy canteen policy that required schools to eliminate unhealthy items from the regular sale and increase those healthy ones.	Direct observations of mean energy, total fat and sodium per student purchase were assessed during one school day.	Intervention schools were more likely to have menus without unhealthy items and to have at least 50% of menu items classified as healthy than control schools. Student purchases from intervention school canteens were lower in total fat but not in energy or sodium than control schools.
Lee et al., 2018 [44]	Group-randomized controlled trial. 1 academic year. OSNAP	400	Mean age: 7–6 years in control group and 7–8 years in intervention group.	Implementation of menus that increased the frequency of fruits; reduced the frequency and servings of juice; removed foods with partially hydrogenated oils; and included more whole grain foods. Healthy habits promotion and nutrition sessions for directors, support staff, families and children	Direct observation and digital photography of type, size and brand of all food and beverage items served each day.	Decrease in the consumption of juice, beverage calories, foods with trans fats, total calories and increase in the consumption of whole grain in intervention group than in control group.
Trude et al., 2018 [45]	Group-randomized controlled trial. 8 months. BHCK	509	9–15 years	Environment modification program and increase in the availability of healthy beverages, snack and cooking methods. Nutrition sessions for children. Promotion of healthy eating through social networks.	CIQ: tool for measuring youth purchasing behavior. BKFFQ: to collect youth food and beverage intake.	There was an increase in the purchase of healthier foods and beverages of 1.4 more items per week in intervention group compared to control group. A decrease in the percentage of calories from sandwiches, sweets and desserts was observed among the 13- to 15-year-olds in the intervention group compared to the control group of the same age range. No differences were found in fruit and vegetables intake.
Vik et al., 2020 [40]	Non-randomized trial 1 academic year. School Meal Project	164	10–12 years	Free healthy school meal at lunch in the intervention group compared with normal lunch in the control group.	FFQ: validated questionnaire used in the Fruits and Vegetables Make the Marks-project.	Higher weekly intake of vegetables on sandwiches adjusted for baseline intake in intervention group compared to control group.
Bartelink et al., 2019 [38]	Longitudinal quasi-experimental trial. 2 years HPSF	1676	4–12 years	(1)Full intervention: free healthy school lunch and mid-morning snack each day + structured PA sessions after lunch. (2)Partial intervention: structured PA sessions after lunch. (3)Control	Questionnaires to assess dietary behaviors and intake filled out by parents and children. Child lunch questionnaire.	Higher intake of vegetables and dairy products and lower intake of grains and butter in the full intervention compared to control. In the partial intervention, lower intake of vegetables, dairy products and butter compared to control intervention. Decrease in time spent sedentary and increase in time spent in light PA in the full intervention compared to control intervention. Improve in children’s healthy dietary behaviors in full intervention compared to control intervention.

PSFBI: Primary School Free Breakfast Initiative; PP: Primary Prevention; PP + SP: Primary Prevention + Secondary Prevention; C: control; LA Health: Louisiana Health study; OPUS School Meal: Optimal well-being, development and health for Danish children through a healthy New Nordic Diet School Meal Study; WebDASC: Web-based Dietary Assessment Software for Children; CHANGE: Creating Healthy, Active and Nurturing Growing-Up Environments study; USDA: United States Department of Agriculture; OSNAP: Out of School Nutrition and Physical Activity study; BHCK: B’more Healthy Communities for Kids study; CIQ: Child Impact Questionnaire; BKFFQ: Block Kids 2004 Food Frequency Questionnaire; CHIRPY DRAGON: Chinese Primary School Children Physical Activity and Dietary Behavior Changes study; SFFQ: Short food frequency questionnaire; HPSF: Healthy Primary School of the Future study; PA: Physical activity; FFQ: Food frequency questionnaire.