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. 2021 Jul;58(7):e13591.
doi: 10.1111/psyp.13591. Epub 2020 Apr 30.

The fitness versus body fat hypothesis in relation to hippocampal structure

Sarah L Aghjayan  1   2 , John M Jakicic  3 , Renee J Rogers  3 , Irene Esteban-Cornejo  4   5 , Jamie C Peven  1   2 , Chelsea M Stillman  1 , Jennifer C Watt  1 , Kirk I Erickson  1   2   6
Affiliations

The fitness versus body fat hypothesis in relation to hippocampal structure

Sarah L Aghjayan et al. Psychophysiology. 2021 Jul.

Abstract

The Fitness Versus Body Fat Hypothesis argues that cardiorespiratory fitness (CRF) plays a more important role in cardiovascular health than adiposity. It remains poorly understood whether CRF or adiposity accounts for a greater amount of variation in measures of brain health. We examined the contribution of CRF, adiposity, and their interaction with hippocampal structure. This study included 124 sedentary adults (M = 44.34) with overweight/obesity (Body Mass Index mean = 32.43). FMRIB's Integrated Registration and Segmentation Tool was used to segment the hippocampus. Using hierarchical regression, we examined whether CRF, assessed via a submaximal graded exercise test, or adiposity, assessed as percent body fat using dual-energy x-ray absorptiometry (DXA) was associated with left and right hippocampal volume. Vertex-wise shape analysis was performed to examine regional shape differences associated with CRF and adiposity. Higher CRF was significantly associated with greater left hippocampal volume (p = .031), with outward shape differences along the surface of the subiculum and CA1 regions. Adiposity was not associated with left or right hippocampal volume or shape. The interaction between adiposity and CRF was not significant. Neither CRF nor adiposity were associated with thalamus or caudate nucleus volumes or shapes, two control regions. Higher CRF, but not adiposity, was related to greater left hippocampal volume, with outward shape differences along the surface of the subiculum and CA1 regions in a midlife sample with overweight/obesity. These findings indicate that, within the context of obesity, CRF is an important contributor to hippocampal structure, highlighting the importance of interventions targeting CRF.

Keywords: anatomical; fitness; hippocampus; middle-aged adults; obesity.

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Conflict of interest statement

CONFLICT OF INTEREST

The authors declare no conflict of interest.

Figures

FIGURE 1
FIGURE 1
(a) Scatter plot of age by CRF as a function of sex. (b) Scatter plot of age by adiposity as a function of sex. (c) Scatter plot of age by left hippocampal volume as a function of sex. (d) Scatter plot of age by right hippocampal volume as a function of sex. Age was not significantly correlated with CRF, adiposity, or hippocampal volume (ranging between r = −.095, p = .291 and r = .003, p = .977)
FIGURE 2
FIGURE 2
Scatter plot of CRF by left hippocampal volume. After accounting for sex, intracranial volume, and adiposity, the relationship between CRF and left hippocampal volume was significant (p = .031)
FIGURE 3
FIGURE 3
Scatter plot of CRF by right hippocampal volume. After accounting for sex, intracranial volume, and adiposity, the relationship between CRF and right hippocampal volume was not significant (p = .694)
FIGURE 4
FIGURE 4
Mapping of significant left hippocampal shape differences related to CRF. Significant differences at each point are displayed using a significance-corrected 1-p value color scale, such that a value of .95 corresponds to p = .05. All analyses controlled for sex and adiposity. Significant outward shape differences were found along the surface of the subiculum and CA1 regions of the left hippocampus. Only the most significant sides of the nuclei are displayed
See this image and copyright information in PMC

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