Background: Previous research has reported a relationship between high protein intake (>15% of energy) during early childhood and an increased risk of obesity later in life. However, few studies have investigated this relationship during middle childhood to early adolescence or examined the effects of different sources of protein.

Objective: The aim of this study was to investigate the relationship between the source of protein intake (animal vs. plant) and body mass index (BMI) in children between the ages 6-14 years.

Participants/setting: 285 healthy 6-14 year old (male n=154) Caucasian and African American (n=171) children from Pittsburgh, Pennsylvania completed a food frequency questionnaire.

Main outcome measures: Median protein intake (grams) by total, animal, and plant protein and BMI-for-age classification.

Statistical analysis: The Kruskal-Wallis test was used to evaluate differences in median protein intake (grams) by weight classification (normal weight [BMI 5^th%ile to <85^th%ile], overweight [BMI 85^th%tile to <95^th%tile], obese [BMI >95^th%tile]). Correlation statistics were also conducted to examine the relationship between protein intake and BMI.

Results: The population used in the data analysis included 285 children/early adolescents (median age 9.8 ± 2.1 years; 53% boys; 40% Caucasian). Data from 11 children were excluded due to outliers or missing data. Girls had a significantly higher BMI than boys (20.1 vs. 18.2 kg/m², respectively; P=P=P=

Conclusions: We observed a significant curvilinear versus linear trend in total protein and animal and plant protein intake by weight classification in middle-aged children that may be due to under-reporting in overweight and obese children. Total percent protein intake was significantly higher in children of normal weight. Future longitudinal studies using multiple measures of body fatness should be conducted to determine the relationship between protein intake and BMI during middle childhood to early adolescence.