. 2015 Dec 10;16:564. doi: 10.1186/s13063-015-1089-z

Table 3.

Average retention rates by study characteristics

	Number of studies	Study enrollment^a	Study retention^b	Average retention rates
Race or ethnicity
Hispanic	5	586	511	82.8
African American	10	1331	1059	83.5
African American, white and other	8	1927	1763	92.1
Intervention target
Children	3	413	388	91.1
Children and parent	20	3431	2945	85.6
Body weight status
Overweight or obese	9	1581	1314	79.6
All weights	10	1523	1334	90.0
Body weight status not measured	4	740	685	92.6
Study type
Prevention	10	1523	1334	90.0
Treatment	13	2321	1999	83.6
Intervention length
<1 year	16	1658	1461	88.6
≥1 year	7	2186	1872	81.1
Study type and treatment length
Prevention <1 year	7	707	614	90.4
Prevention ≥1 year	3	816	720	88.8
Treatment <1 year	9	951	847	87.2
Treatment ≥1 year	4	1073	873	74.0
Primary outcome
BMI or anthropometrics	10	2342	2026	82.9
Other (behavior, physiology, etc.)	13	1502	1307	89.0
Intervention setting^c
School	5	1273	1151	91.7
Home or community	15	2410	2051	85.5
Laboratory	2	126	102	81.1
Main intervention group
Nutrition or physical activity	4	755	712	92.8
Nutrition and physical activity	19	3089	2621	85.0
Study design
Randomized controlled trial	19	2739	2440	89.3
Cluster randomized controlled trial	2	745	656	75.6
Controlled trial	1	235	136	57.9
Trial without control	1	125	101	80.8
Mean age of children^d
<12 years	15	2708	2333	86.2
≥12 years	8	1136	1000	86.7
Number of intervention sessions^e
≤12	7	752	636	86.3
≥13	15	2840	2445	85.5
Sample size
<100	9	493	435	86.9
≥100	14	3351	2898	86.0

^aThe sum of numbers of participants enrolled in individual studies

^bThe sum of numbers of participants retained in individual studies

^cIntervention setting was not reported in the study by Weigensberg et al. [28]

^d<12 years group includes one study with participants aged 8–14 years; ≥12 years group includes one study with participants aged 9–14 years, one study with participants aged 10–17 years and two studies with participants aged 11–16 years

^eNumber of intervention sessions was not reported in the study by Azevedo et al. [17]