Intra-Abdominal Fat and Risk of Disease in Adolescents
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.
Interventional
Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Factorial Assignment, Masking: Open Label, Primary Purpose: Prevention
insulin sensitivity
post intervention (week 16)
No
Michael I Goran, PhD
Principal Investigator
University of Southern California
United States: Federal Government
5R01HD33064-13
NCT00697580
May 2005
July 2007
Name | Location |
---|---|
Veronica Atkins Lifestyle Intervention Laboratory | Los Angeles, California 90033-9073 |