Energy Balance Interventions for Colorectal Cancer Prevention

OBJECTIVES:

• To compare four 12-week energy-balance interventions comprising a physical activity intervention (+2,000 kcal/wk), a dietary energy restriction intervention (DER)(-2,000 kcal/wk), or a combined physical activity and DER intervention (+1,000/-1,000 kcal/wk) vs no intervention in healthy, overweight, or moderately obese participants at increased risk for developing colorectal cancer.
• To quantify changes in circulating biomarkers (e.g., insulin, IGF-1, leptin, c-reactive protein, or isoprostanes) proposed to mediate the anticarcinogenic effects of DER in these participants.

OUTLINE: This study consists of a 2-week run-in period (baseline) followed by a 12-week intervention period.

Participants undergo three study visits at Vanderbilt University General Clinical Research Center (GCRC). Beginning at study visit 1, participants undergo a 2-week run-in period to obtain baseline measures of body composition (via dual x-ray absorptiometry), cardiorespiratory fitness (via treadmill testing), physical activity, dietary intake, energy expenditure, and metabolic activity. Dietary assessments using 24-hour dietary recalls are conducted by the GCRC dietitian during the run-in period. GCRC dietitians complete three 24-hour recalls on randomly selected days during the 2-week assessment period to provide an estimate of the participant's habitual food intake at baseline. Baseline energy needs are assessed during activity monitored run-in period to obtain measures of the participant's resting energy expenditure and total daily energy expenditure. Participants are also assessed using a brief psychological profile that is used to individualize the study intervention for each participant.

Approximately 10-14 days after the initial visit and after all baseline assessments have been completed, participants undergo a second study visit. Participants are randomized to 1 of 4 intervention arms.