Strength and Nutrition Outcomes for Latino Adolescents
Condition: Obesity; Type 2 Diabetes; Cardiovascular Risk; Cancer
MeSH terms: Diabetes Mellitus, Type 2
Study type: Interventional

Summary: 
      We 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
      Latino youth. Eighty overweight Latino 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), 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) or 4) Combination of Circuit
      Training (twice/week for 60 min, aerobic + strength training exercises) + Dietary Education
      (same as above). We will assess which intervention group has the most effects on health
      parameters such as weight, body composition, and insulin related measures.
    

Detailed description: 
      The overall historical goal of this grant has been to examine the determinants of insulin
      resistance in children, especially the role of total fat and visceral fat during pubertal
      development in "high risk" minority children. Our previous longitudinal work has provided the
      platform to propose a new intervention phase of this research. This new emphasis is justified
      based on the magnitude of the pediatric obesity problem, particularly in susceptible ethnic
      groups, and the need to design and test novel interventions to reduce not just obesity, but
      the profound insulin resistance that we have observed in overweight minority children.
      Insulin resistance is thought to be central (and perhaps causative) to several metabolic
      abnormalities associated with type 2 diabetes and cardiovascular disease. Thus, interventions
      aimed at improving insulin resistance in susceptible children could be an effective means in
      the primary prevention of type 2 diabetes and cardiovascular disease.

      The overall objective of this proposal is therefore to conduct a randomized controlled study
      to examine the effects of 16-week exercise and diet interventions on insulin sensitivity,
      insulin secretion, beta-cell function, and body fat distribution. Overweight Hispanic boys
      and girls (n=80) will be recruited and randomized to one of the following interventions:

      Ø Control (delayed intervention) Ø Modification of carbohydrate intake (reduced sugar & soda,
      increased fiber & whole grain intake) using an individualized healthy exchange system and
      motivational interviewing Ø Strength training + modification of carbohydrate intake Ø Circuit
      Training + modification of carbohydrate intake

      This study will provide new information on the effects of these interventions on primary
      outcomes at the level of body composition (total lean and fat mass, visceral fat,
      intramyocellular fat and liver fat) and insulin related measures (insulin secretion &
      sensitivity and beta-cell function). The hypotheses are:

        1. All interventions will have separate and independent effects on improving insulin
           resistance

        2. Strength training will improve insulin resistance by re-distribution of body fat (lower
           visceral fat, intramyocellular lipid and liver fat)

        3. Carbohydrate modification will improve insulin secretion and beta-cell function

        4. Circuit training will have similar improvements in insulin resistance and have more
           improvements on adiposity compared to the strength training group.

        5. The aforementioned effects on insulin dynamics will be independent of any effects of
           either intervention on weight loss or loss in whole body fat.

      The overall rationale for these interventions is based on three main factors. First,
      preliminary data are presented in overweight Hispanic boys showing that 16-weeks of strength
      training significantly improves insulin sensitivity in the absence of a reduction in total
      body fat and in the absence of any dietary intervention. Second, preliminary data suggests
      that overweight Hispanic children consume high levels of simple sugar, and low levels of
      fiber and complex carbohydrates, and data from the literature suggests that modification of
      carbohydrate consumption (reduced sugar, increased fiber & whole grain) can improve glucose
      control independent of body composition. Third we provide new preliminary data showing that
      the only dietary variable associated with insulin dynamics in overweight Hispanic children
      was high sugar intake which was associated with poor beta-cell function.

      We have chosen to focus on Hispanic children because they are an understudied, high-risk
      population, and display significant obesity-related metabolic abnormalities probably
      emanating from profound insulin resistance (see preliminary data). In support of the
      feasibility of our proposal, we have developed extensive expertise in recruiting and
      retaining research volunteers from the large Hispanic population of East Los Angeles, we have
      an experienced multi-disciplinary group of investigators, and the University of Southern
      California has the necessary clinical research infrastructure to tackle this project. If our
      hypotheses are borne out, it will provide evidence for the incorporation of strength training
      and more specific and individualized dietary recommendations in the prevention and management
      of obesity, type 2 diabetes, and cardiovascular risk in overweight Hispanic youth.
    

Intervention name(s): Nutrition; Strength Training & Nutrition; Circuit Training & Nutrition
Intervention type(s): Behavioral; 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); Circuit 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; Latino; Adolescents; Strength Training; Circuit Training; Nutrition