Strength Training and Nutrition Development for African American Youth
Condition: Obesity; Type 2 Diabetes; Cardiovascular Risk; Cancer
MeSH terms: Obesity; Diabetes Mellitus, Type 2
Study type: Interventional

Summary: 
      The investigators are conducting an intervention study to examine the effects of a 16-week
      exercise and diet interventions on prevention of disease, specifically type 2 diabetes and
      heart disease, in African American youth. Sixty overweight African American boys and girls
      will be recruited and placed in one of the following intervention groups: 1) Control Group
      (delayed intervention), 2) Dietary Education Group (nutrition education focused on reducing
      sugar & soda, increased fiber & whole grain intake), or 3) Combination of Strength Training
      (twice/week for 60 min, progressive increases in exercise volume and intensity) + Dietary
      Education (nutrition education focused on reducing sugar & soda, increased fiber & whole
      grain intake). The investigators will assess which intervention group has the most effects on
      health parameters such as weight, body composition, and insulin related measures.
    

Detailed description: 
      A.1 Aims

      The overall goal of this project is to examine role of strength training as a therapeutic
      intervention to improve the cancer and obesity-related metabolic risk profile in
      African-American adolescents. The project is prompted by the urgent public health need to
      prevent and treat cancer and obesity-related problems, including diabetes and cardiovascular
      disease, in African-American adolescents, a population that is understudied and medically
      under-served in the Los Angeles area. A recent report from the Institute of Medicine
      underscored this major public health concern in the childhood obesity field:

      "Children's health has made tremendous strides over the past century. In general, life
      expectancy has increased by more than thirty years since 1900 and much of this improvement is
      due to the reduction of infant and early childhood mortality. Given this trajectory toward a
      healthier childhood, the investigators begin the 21st century with a shocking development -
      an epidemic of obesity in children and youth. The increased number of obese children
      throughout the US during the past 25 years has led policymakers to rank it as one of the most
      critical public health threats of the 21st century. (92)" Obesity and metabolic syndrome
      problems disproportionately affect African-American adolescents (51). This project will
      explore why African-Americans have greater cancer risk than Hispanics (91), despite a reduced
      prevalence of the metabolic syndrome (7, 62).

      Preliminary work from this laboratory has shown that both African-American and Hispanic
      children are more insulin resistant than Caucasian children, and this difference is
      apparently not explained by differences in body fatness. Moreover, the metabolic compensation
      to a similar degree of insulin resistance markedly differs between African-American and
      Hispanic children (62). African-Americans display greater hyperinsulinemia in response to a
      glucose challenge, whereas Hispanics have a more subdued increase in insulin levels due to an
      increase in second phase insulin secretion. The investigators will have the opportunity to
      build upon this preliminary work to examine the effects of resistance training on three
      factors predictive of cancer and metabolic disease risk: 1) body fat distribution; 2) insulin
      resistance and 3) measures of oxidative stress in African America adolescents. The
      investigators previously studying Hispanic adolescents in a parallel protocol.

      The overall hypotheses of this project are that: (1) hyperinsulinemia in overweight
      African-American youth is associated with increased long-term cancer risk; and (2) insulin
      resistance, obesity and oxidative stress in overweight African-American youth will be
      improved with chronic resistance training and a modified carbohydrate dietary approach. The
      investigators will specifically examine the following metabolic outcomes, because they have
      been hypothesized to contribute to the obesity-related increase in cancer and metabolic
      disease risk:

        -  Insulin concentrations and insulin sensitivity;

        -  Total body fat, abdominal visceral fat, muscle fat and liver fat;

        -  Circulating adipocytokines;

        -  Intima-media thickness of the carotid artery

        -  Markers of oxidative stress, including: F2-isoprostanes, malondialdehyde (MDA),
           myeloperoxidase (MPO), oxygen radical absorbance capacity and ROS detection by flow
           cytometry.

      A.2 Aims

      The specific aims and hypotheses of project 1 are as follows:

      Study 1: Cross-Sectional Measures Specific Aim 1 (Body Fat Compartments): To determine the
      association of visceral fat, muscle and liver fat and plasma adipocytokines to variation in
      insulin resistance in African-American youth.

        -  Hypothesis 1: Visceral fat, muscle and liver fat, and adipokines will independently
           contribute to greater insulin resistance.

           • Specific Aim 2 (Insulin Resistance): To examine metabolic compensation to insulin
           resistance in African-American youth.

        -  Hypothesis 2: Insulin resistant African-American youth will exhibit a higher acute
           insulin response to glucose.

           • Specific Aim 3 (Oxidative Stress): To examine the influence of body fat and insulin
           resistance on markers of oxidative stress and markers of metabolic disease risk.

        -  Hypothesis 3: Increased total body fat and insulin resistance will be associated with
           greater oxidative stress. The increased oxidative stress will be correlated with the
           higher acute insulin response.

      Study 2 (Randomized Trial of Modification of Carbohydrate Intake and Strength Training) •
      Specific Aim 4 (Linkage of factors in Aims 1-3): To determine the effects of a randomized
      modification of carbohydrate intake, and/or strength training intervention in overweight
      African-American adolescents on potential factors linking obesity, insulin resistance, and
      oxidative stress.

      - Hypothesis 4: Strength training will improve metabolic factors for cancer risk. That is,
      resistance training will reduce visceral fat; increase insulin sensitivity, reduce
      hyperinsulinemia, and reduce oxidative stress. The decreases in total body fat and visceral
      adipose tissue will be associated with improved insulin sensitivity and oxidative stress.
    

Intervention name(s): Nutrition; Strength Training & Nutrition
Intervention type(s): Behavioral; Behavioral
Intervention description(s): Nutrition classes for 1 hour & 30 minutes once a week for 16 weeks + motivational interviewing (4 individual sessions); Strength Training twice a week for 1 hour a day for 16 weeks + Nutrition once a week for 1 hour & 30 minutes for 16 weeks + motivational interviewing (4 individual & 4 group sessions)
Allocation: Randomized
Intervention model: Factorial Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Obesity; Type 2 Diabetes; Cardiovascular Risk; Cancer; African American; Adolescents; Strength Training; Nutrition