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Biological Effects of Weight Loss In Older, Obese Women

2014-08-27 03:17:17 | BioPortfolio

Summary

Obesity and sedentary lifestyle are associated with physical impairments and biological changes in older adults. Weight loss combined with exercise may reduce inflammation and may improve physical functioning in older adults who are overweight or obese and sedentary. However, the mechanisms by which weight change and exercise influence physical functioning and sarcopenia remain largely understudied. Participants (N=34) were generally healthy obese, older adult women (age range = 55 - 79) with mild to moderate physical impairments (i.e., functional limitations). Participants were randomly assigned to one of two groups for 24 weeks: 1) weight loss plus exercise (WL+E; n = 17; mean age = 63.7 years [4.5]) or 2) educational control (n = 17; mean age =63.7 [6.7]). In the WL+E group, participants attended a group-based weight management session plus three supervised exercise sessions each week throughout the entire study. During each exercise session, participants engaged in both aerobic activities (i.e., walking) and lower body resistance training of moderate intensity. The participants in the educational control group attended monthly health education lectures on topics relevant to older adults. It was hypothesized that participants assigned to the WL+E intervention would 1) lose a larger amount of weight, 2) improve their physical function levels, and 3) reduce levels of oxidative stress and inflammation to a greater degree than participants assigned to the Educational Control group. Outcomes are: 1) body weight, 2) walking speed (assessed by 400 meter walk test), 3) the Short Physical Performance Battery [SPPB], and 4) knee extension isokinetic strength. The objectives of this pilot study are fourfold: 1) to demonstrate the feasibility, acceptability, and efficacy of the proposed WL+E intervention in a sample of 40 sedentary, obese older adults with impaired physical functioning; 2) to examine the biological effects of the intervention on inflammatory processes, oxidative stress, apoptosis, sarcopenia, muscle and body composition, muscle strength, and functional performance; 3) to determine whether the expected beneficial effects of the WL+E intervention on physical functioning are mediated by changes in inflammation, apoptosis, and sarcopenia; and 4) to determine the effect size of the WL+E intervention on key outcomes and provide the basis for sample size calculations in the planning of a larger RCT.

Description

SPECIFIC AIMS A.1. Overview Obesity is associated with a higher level of inflammation and oxidative stress, which in turn are important mediators of sarcopenia, declines in physical functioning, and physical limitations in older adults. Several observational studies and randomized controlled trials (RCTs) suggest that behavioral interventions targeting weight loss through caloric restriction plus exercise (CR +EX) may reduce inflammation and may improve function in obese older adults.3 The mechanisms by which CR +EX may influence physical functioning and sarcopenia (the involuntary loss of skeletal muscle with age) remain largely understudied. It is proposed that CR +EX may avert sarcopenia by reducing inflammation, oxidative damage, and consequent apoptosis of skeletal muscle myocytes.

A.2. Objective of the Pilot Study

The proposed pilot study will lay the groundwork for a RCT of the effects of CR +EX on inflammation, oxidative stress, apoptosis, body composition, intramuscular fat, sarcopenia, muscle strength, and physical functioning in obese older adults. The specific objectives of the proposed study are as follows:

1. Demonstrate the feasibility, acceptability, and efficacy of the proposed intervention, including:

1. Ability to recruit 40 sedentary, older obese adults with mild to moderate functional disability;

2. High rate of attendance at treatment sessions (Mean > 75%); and

3. Good response to treatment (Mean body weight loss > 7%).

2. Evaluate the biological effects of the CR +EX intervention, including changes in:

1. Inflammation (i.e., tumor necrosis factor-α [TNF- α], interleukin-6 [IL-6], myeloperoxidase [MPO]);

2. Oxidative stress (RNA and DNA oxidative damage in leucocytes)

3. Apoptosis (as assessed by caspases and nuclear DNA fragmentation);

4. Body composition (as assessed by dual x-ray absorptiometry [DXA)] and

5. Sarcopenia and muscle composition (i.e., fat free muscle and intramuscular fat, as assessed by Magnetic Resonance Imaging [MRI] and Magnetic Resonance Spectroscopy [MRS]).

3. Examine functional changes associated with weight loss including:

1. Upper and lower extremity muscle strength (as measured by grip strength and isometric and isokinetic ankle and knee strength);

2. Response to the Short Physical Performance Battery; and

3. Self-reported disability.

4. Test whether the expected beneficial effects of the CR +EX intervention on physical functioning are mediated by changes in inflammation, oxidative stress, apoptosis, and sarcopenia;

5. Determine the effect size of the CR +EX intervention on the key outcomes so as to provide the basis for sample size calculations for the planning of the larger RCT.

A.3. Research Hypotheses for the Future RCT

The synergistic effects of CR +EX may be effective in reversing the effects of inflammation, oxidative distress, apoptosis, and sarcopenia on both muscle strength and physical functioning in older adults. Thus, the primary goal of this pilot study is to provide support for a future RCT to test the hypothesis that a lifestyle intervention targeting a 7% loss in body weight through CR + EX will produce greater reductions in these outcomes, as compared to a (no weight loss) control condition. The future RCT would be designed to test the following primary and secondary hypotheses:

Primary hypotheses. As compared with a control condition, the CR +EX Intervention will:

1. Decrease inflammation (as measured by TNF-α, IL-6, and MPO);

2. Decrease oxidative stress (as measured by DNA and RNA damage in isolated leucocytes);

3. Decrease the rate of apoptosis (as measured by caspases and DNA laddering);

4. Produce favorable changes in body composition (i.e., a decrease in total fat mass and an increase in appendicular lean mass, as assessed by DXA); and

5. Produce favorable changes in muscle composition (i.e., a decrease in intramuscular fat and an increase in fat-free muscle as assessed by MRI/MRS).

6. Increase muscle strength and performance (as assessed through validated strength measures)

Study Design

Allocation: Randomized, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Parallel Assignment, Primary Purpose: Treatment

Conditions

Obesity

Intervention

Lifestyle Counseling, Educational Control

Location

University of Florida
Gainesville
Florida
United States
32611

Status

Completed

Source

University of Florida

Results (where available)

View Results

Links

Published on BioPortfolio: 2014-08-27T03:17:17-0400

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