Energy Restriction and Hormones in Premenopausal Women

Summary

A growing body of epidemiological and biological evidence strongly suggests that physical activity may reduce the risk of breast cancer. Although the mechanism remains unclear, possible links between reduced risk and exercise include favorable alterations in body composition and positive changes in the hormonal milieu. One hormonal biomarker of breast cancer, circulating estrogen, is postulated to be reduced by chronic physical activity, presumably due to disruptive effects of exercise upon menstrual cyclicity, and the potential for loss of body fat with subsequent reductions in the peripheral biosynthesis of circulating estrogens. Although studies have shown that chronic exercise can reduce circulating estrogen, we know little about the magnitude and duration of exposure to an energy deficit required for these changes. Additionally, no studies have addressed the degree to which peripheral production of estrone, versus the ovarian production of estradiol, is altered with exercise that promotes weight/fat loss. A second biomarker of breast cancer, insulin-like growth factor-1 (IGF-1), is presumably increased with exercise but reduced with exercise if energy balance is negative. No prospective studies have addressed whether a moderate aerobic exercise program that results in weight loss will lead to significant changes in IGF-I levels, particularly in individuals of differing initial energy stores.

Metabolic energy availability is an important contributing factor in the development of reproductive cancers. However, current methods for assessing energy availability, which include anthropometric measures, calculations of energy balance, evaluation of various serum and urinary biomarkers are prone to measurement error, not sensitive to alterations in energy availability, and are sometimes affected by disease states. The current project includes the introduction of a novel approach to estimating energy status by measuring metabolic hormones in plasma: insulin, IGF-I, insulin-like growth factor binding protein-3 (IGFBP-3) and leptin.

This study tested whether a program of moderate aerobic exercise that is combined with a moderate level of dietary restriction would result in significant decreases in two biomarkers of breast cancer, circulating estrogens and IGF-I.

Conditions

• Menstruation Disturbances
• Luteal Phase Defect

Interventions

OTHER

Exercise+CR

Exercise with caloric-restriction

OTHER

Light Conditioning

Light Conditioning Exercise

Sponsors & Collaborators

• National Institutes of Health (NIH)

  collaborator NIH

• United States Department of Defense

  collaborator FED

• National Center for Research Resources (NCRR)

  collaborator NIH

• Penn State University

  lead OTHER

Principal Investigators

• Nancy Williams, ScD · Penn State University

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

NONE

Model

PARALLEL

Eligibility

Min Age

25 Years

Max Age

40 Years

Sex

FEMALE

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2001-03-31

Primary Completion

2006-11-30

Completion

2006-11-30