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Diet-Induced Weight Loss alters Functional Brain Responses during an Episodic Memory Task
Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS).ORCID iD: 0000-0002-4458-6475
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
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2015 (English)In: Obesity Facts, ISSN 1662-4025, E-ISSN 1662-4033, Vol. 8, 261-272 p.Article in journal (Refereed) Published
Abstract [en]

Objective: It has been suggested that overweight is negatively associated with cognitive functions. The aim of this study was to investigate whether a reduction in body weight by dietary interventions could improve episodic memory performance and alter associated functional brain responses in overweight and obese women. Methods: 20 overweight postmenopausal women were randomized to either a modified paleolithic diet or a standard diet adhering to the Nordic Nutrition Recommendations for 6 months. We used functional magnetic resonance imaging to examine brain function during an episodic memory task as well as anthropometric and biochemical data before and after the interventions. Results: Episodic memory performance improved significantly (p = 0.010) after the dietary interventions. Concomitantly, brain activity increased in the anterior part of the right hippocampus during memory encoding, without differences between diets. This was associated with decreased levels of plasma free fatty acids (FFA). Brain activity increased in pre-frontal cortex and superior/middle temporal gyri. The magnitude of increase correlated with waist circumference reduction. During episodic retrieval, brain activity decreased in inferior and middle frontal gyri, and increased in middle/superior temporal gyri. Conclusions: Diet-induced weight loss, associated with decreased levels of plasma FFA, improves episodic memory linked to increased hippocampal activity.

Place, publisher, year, edition, pages
2015. Vol. 8, 261-272 p.
Keyword [en]
Functional magnetic resonance imaging, Episodic memory, Obesity, Diet interventions, Hippocampus
National Category
Neurosciences Nutrition and Dietetics
URN: urn:nbn:se:umu:diva-101039DOI: 10.1159/000437157ISI: 000360933400004PubMedID: 26139105OAI: diva2:796149
Available from: 2015-03-18 Created: 2015-03-18 Last updated: 2016-09-28Bibliographically approved
In thesis
1. Brain function and glucocorticoids in obesity and type 2 diabetes including effects of lifestyle interventions
Open this publication in new window or tab >>Brain function and glucocorticoids in obesity and type 2 diabetes including effects of lifestyle interventions
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Effekter av livsstilsförändring på hjärnfunktion och stresshormoner vid fetma och typ 2 diabetes
Abstract [en]

Background Obesity and associated metabolic dysregulation are linked to impaired cognitive function and alterations in brain structure, which increases the risk of age-related dementia. Increased glucocorticoid (GC) exposure may be a potential mediator of these negative effects on the brain.

Methods and results In paper 1, we tested the relationship between cortisol levels, brain morphology and cognitive function in 200 women and men. Salivary cortisol levels were negatively related to cortical surface areas in prefrontal brain regions in both sexes. In participants with type 2 diabetes, high salivary cortisol levels were associated with lower memory performance. In paper 2, we tested in 70 overweight women the effects on tissue-specific GC metabolism of a Paleolithic diet or a diet following the Nordic nutrition recommendations. The 24-month interventions led to decreased expression of the GC-activating enzyme 11βHSD1 in adipose tissue, interpreted as a normalization of an obesity-related disturbance in GC metabolism. Furthermore, GC metabolism by 5α-reductase increased substantially after 2 years, an unexpected and novel result. The outcomes did not differ by diet. In paper 3, 20 women included in paper 2 were examined with functional magnetic resonance imaging (fMRI) while performing a memory task at baseline and after 6 months. Memory performance improved and functional brain responses increased in the hippocampus. Once again, the results were similar in both diet groups. In paper 4, 24 overweight participants with type 2 diabetes were examined with fMRI, using the same memory test as in paper 3, at baseline and after 12 weeks of intervention with a Paleolithic diet with or without exercise training. Functional brain response increased in the hippocampus, but memory was not improved. The addition of physical exercise did not alter the results.

Conclusion Cortisol levels are linked to prefrontal brain structure and, at least in type 2 diabetes, lower memory performance. Furthermore, the dysregulated GC metabolism in obesity can be reversed by long-term diet- induced weight loss. Finally, dietary interventions with associated metabolic improvements alter functional brain responses during memory testing, including increased activation of the hippocampus. Whether these changes are linked to alterations in GC exposure and mediate improved cognition requires further study. 

Place, publisher, year, edition, pages
Umeå: Umeå University, 2015. 85 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1710
Obesity, type 2 diabetes, glucocorticoid, cortisol, 11beta hydroxysteroid dehydrogenase type 1, episodic memory, functional magnetic resonance imaging, paleolithic diet, exercise
National Category
Endocrinology and Diabetes Neurosciences
Research subject
Internal Medicine; Medicine
urn:nbn:se:umu:diva-102596 (URN)978-91-7601-250-5 (ISBN)
Public defence
2015-05-27, Bergasalen, Norrlands Universitetssjukhus, Umeå, 13:00 (English)
Available from: 2015-05-06 Created: 2015-04-28 Last updated: 2016-05-27Bibliographically approved

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Boraxbekk, Carl-JohanStomby, AndreasRyberg, MatsLindahl, BerntLarsson, ChristelNyberg, LarsOlsson, Tommy
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