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United States Department of Agriculture

Agricultural Research Service

Research Project: Physical Activity Interventions to Prevent Childhood Obesity

Location: Children's Nutrition Research Center

2011 Annual Report


1a.Objectives (from AD-416)
Objective 1: Determine obesity-related metabolic and body composition responses to an exercise program with and without a dietary intervention in lean and obese Hispanic adolescents. Sub-objective 1A: Determine the effects of a combined aerobic and resistance exercise program on lean body mass and total fat mass (using DXA), visceral and hepatic fat accumulation using Magnetic Resonance Imaging (MRI) and Magnetic Resonance Spectroscopy (MRS); and glucose and lipid metabolism and insulin sensitivity using Stable Isotope-Gas Chromatography Mass Spectrometry (GCMS) techniques in lean and obese adolescents. Sub-objective 1B: Determine the effects of a combined aerobic and resistance exercise program + a diet intervention aiming at a 5% weight loss on lean body mass, total fat mass, visceral and hepatic fat; glucose and lipid metabolism and insulin sensitivity in obese adolescents (using the same techniques as in Sub-objective 1A). Objective 2: Develop and pilot test interventions to increase and sustain physical activity at a level consistent with the Dietary Guidelines for Americans (DG) in urban African- and Mexican-American children. Sub-objective 2A: Determine if adherence to the physical activity component of the DG is associated with a lower incidence of overweight/obesity in urban African- and Mexican-American children. Sub-objective 2B: Develop and pilot test an intervention with urban African- and Mexican-American children to increase physical activity consistent with the DG recommendation. Specifically, physical activity will be operationally defined as moderate to vigorous physical activity. Sub-objective 2C: Develop and pilot test a maintenance program with urban African- and Mexican-American children to sustain physical activity consistent with the DG recommendation. Specifically, physical activity will be operationally defined as moderate to vigorous physical activity.


1b.Approach (from AD-416)
Research subjects will participate in a whole-body resistance training program and perform a 30-min aerobic exercise program under supervision of experienced exercise physiologists. Additionally they will perform one 30-min aerobic exercise session/week at home. An additional group of research subjects will perform the same training program except a weight loss diet intervention will be added to the exercise program. The subjects will have an in-depth interview with a dietitian to determine eating habits and food preferences and a 3-d food diary will be provided. A sample of 200 African- or Mexican-American middle school children (i.e., 6th – 8th grade; aged 10-15 years will be recruited from a Houston charter school to provide data on their participation in moderate to vigorous physical activity (MVPA). Measured body composition (i.e., height, weight, BMI, percent body fat) will be collected. This study will examine children's free-living participation in physical activity (PA) to determine if these behaviors are consistent with the Dietary Guidelines for Americans (DG) (i.e., 60 minutes of MVPA most days of the week). A questionnaire will be administered identifying PA barriers and facilitators to help determine activities most likely to encourage continued participation in PA. Subjects will be assessed to determine their level of adherence to PA that is consistent with the DG.


3.Progress Report

For Obj. 1, one obese 14-year-old boy and one obese 16-year-old girl have completed the 12-week exercise program (2 hours of strength exercise and 1 hour of aerobic exercise/week) and the two metabolic studies (before and at completion of the program). Both subjects attended more than 90% of the exercise sessions and performed very well. Preliminary results show an 80% increase in upper body muscle strength, 65% increase in leg muscle strength, and 50% increase in arm muscle strength, with no difference between the subjects. The girl showed a greater increase in fitness as measured by oxygen uptake during a tread mill test as compared to the boy. In contrast, the boy showed greater improvement in body composition than the girl. Most of the metabolic analyses are underway. In addition, one obese 15-year-old boy has completed 7 weeks of the exercise program and the pre-exercise metabolic study. This subject and a fourth subject, an obese 14-year-old girl, have been recruited and will complete the study by the end of the FY. In Obj. 2, a sample of 200 middle school children were recruited for participation in the study. Students' level of engagement in physical activity was measured using accelerometry and self report of participation in physical activity. Students' heights and weights were also measured in order to compute standardized body mass index and determine a child's BMI percentile. Bioelectrical impedance data was collected in order to determine students' percentage of body fat. Preliminary analyses indicate that as zBMI and percent body fat increase, participation in very hard and hard physical activity decreases. A sample of 59 participants were recruited to participate in pilot testing a physical activity intervention designed to increase moderate to vigorous activity in children in order to meet dietary guideline recommendations of 60 minutes of physical activity daily. Students receiving the physical activity intervention increased the percentage of minutes spent engaged in hard to very hard physical activity. This intervention was determined to be acceptable to participants. Further analyses are needed to determine whether there was a significant increase in vigorous physical activity compared to students in the control condition. These same 59 participants were recruited to participate in pilot testing of a follow-up program implemented to encourage either continued participation at the level attained during intervention or to continue to increase physical activity to meet dietary guidelines. Data from accelerometry and self-reported participation in physical activity was collected. Participants appeared to maintain their level of physical activity over time. The ADODR monitors project activities by visits, review of purchases of equipment, review of ARS-funded foreign travel, and review of ARS funds provided through the SCA.


4.Accomplishments
1. Helping minority children meet physical activity recommendations. The prevalence of obesity in children and adolescents has quadrupled over the last 4 decades, and obesity rates among minority groups are increasing at even greater rates. Lifestyle interventions that involve diet, physical activity, and behavioral components have been shown to be effective in the treatment of obesity and its co-morbidities, but several barriers to these interventions exist for minority groups, particularly lower social support for participation in physical activity, unsafe neighborhoods, and fewer resources in terms of time and money to spend on participation in physical activity. Researchers at the Children's Nutrition Research Center, Houston, TX, have developed a physical activity intervention and maintenance program for minority students designed to increase their participation in moderate to vigorous physical activity. We have found that students involved in this program were more likely to participate in school sports, and our results suggested that school-based sports participation may enhance maintenance efforts for school-based weight loss interventions. This intervention program may serve as a model to engage other minorities to help them adhere to the current dietary guidelines that recommend children should spend 60 minutes a day engaged in physical activity.


Last Modified: 4/21/2014
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