Date of Award

January 2023

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Leah M. Ferrucci

Second Advisor

Melinda L. Irwin

Abstract

Background and Purpose: Evidence supports a beneficial effect of calorie restriction on longevity within numerous animal models, while data for humans is limited to intermediate biomarkers of aging. The purpose of this study was to determine the association between calorie restriction in humans with respect to hand grip strength, a biomarker of aging and longevity, that has been understudied in relation to caloric restriction. Methods: We analyzed hand grip strength among 184 individuals enrolled in the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE), a 2-year randomized trial of 25% calorie restriction vs. control. Peak hand grip strength was assessed by hand dynamometer as an average of 3 measurements at each time point; a higher value equates to greater strength and a marker of lower aging. Differences in percent change peak force grip strength from baseline to 24 months between the study groups was assessed via t-tests and ANCOVA. We used linear regression with backward stepwise selection to determine characteristics associated with baseline grip strength. We then evaluated potential effect modification by any factors associated with baseline grip strength in both hands as well as handedness and physical activity level. Results: There was no statistically significant difference between the percent change in peak force from baseline to month 24 by study arm for either the left or (Intervention: -3.53%, Control: -5.08%, p=0.633); right hand (Intervention: -1.58%, Control: -2.77%, p=0.710). Only male sex was positively associated with baseline grip strength is both hands (left & right; p < 0.001). There was no evidence effect modification of the intervention effect on grip strength by sex, handedness, or physical activity levels. Conclusions: Though we did not see evidence for an improvement in hand grip strength as a biomarker of aging in this caloric restriction study in humans, this was not a primary outcome of CALERIE and so we were not powered to detect small changes. Further research in larger trials with better adherence to caloric restriction are needed in order to understand if grip strength could be impacted by calorie intake. Better understanding of the effects of calorie restriction can lead to the development of low cost, non-invasive, therapeutic treatments for age-related disease and specific dietary plans can be used to potentially combat disease etiology and delay prognosis.

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This is an Open Access Thesis.

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