Visceral Fat Metabolism Linked to Brain Network Dysfunction, Cognitive Impairment in Alzheimer’s

A new study using whole-body metabolic imaging has linked unusually active visceral fat—the energy-storing tissue packed around abdominal organs—with disrupted brain-network metabolism and poorer cognitive performance in people with Alzheimer’s disease. The findings, reported by researchers at The First Affiliated Hospital of Shandong First Medical University and collaborators, suggest that the biological relationship between the brain and body fat may be more specific than a simple association with obesity. In particular, glucose uptake in visceral adipose tissue was associated with weakened coordination between the brain’s default mode network and several other large-scale systems, as well as lower scores on standard tests of memory and thinking. The work offers a striking view of Alzheimer’s disease as a disorder involving interconnected metabolic systems throughout the body, rather than a condition confined to the brain.

The researchers studied 149 people in total: 98 patients with Alzheimer’s disease and 51 cognitively normal controls. All participants underwent total-body positron emission tomography combined with computed tomography, or 18F-FDG PET/CT. The technique uses fluorodeoxyglucose labeled with fluorine-18, a radioactive molecule that behaves similarly to glucose. After injection, tissues that consume more glucose accumulate more of the tracer, allowing the PET scanner to produce a map of metabolic activity. Because the examination covers the entire body, the investigators could compare glucose use in visceral adipose tissue, located deep within the abdomen, with activity in subcutaneous adipose tissue, the fat stored beneath the skin. They corrected the PET measurements for lean body mass, generating standardized uptake values known as SULs that provide a more consistent estimate of tissue metabolism across individuals.

The distinction between visceral and subcutaneous fat is biologically important. Subcutaneous fat can serve as a relatively passive energy reservoir, whereas visceral fat is more metabolically active and releases fatty acids, hormones and inflammatory signaling molecules into the circulation. It also lies close to the portal circulation, which carries blood from abdominal organs to the liver. Excessive or dysregulated visceral fat has been associated with insulin resistance, abnormal lipid metabolism and chronic low-grade inflammation. Those processes can influence blood vessels, immune signaling and the blood–brain barrier, the selective interface that regulates movement of substances between the circulation and brain tissue. The new study does not establish that visceral fat causes Alzheimer’s disease, but it identifies a measurable metabolic signature that tracks with changes in brain organization and cognition.

To investigate the brain, the team applied independent component analysis to the PET images. This computational method separates complex patterns of coordinated activity into spatially distributed components, allowing researchers to identify metabolic networks rather than examining isolated brain regions one at a time. Among the networks detected were the default mode network, or DMN, the dorsal attention network, the frontoparietal network and the sensorimotor network. The DMN is active during internally focused thought, autobiographical memory and the integration of information, while the attention and frontoparietal systems help direct cognition, maintain goals and process external demands. The sensorimotor network supports movement and the interpretation of bodily sensations. For each participant, the researchers calculated a metabolic load score for these networks, reflecting how strongly an individual’s PET pattern expressed the network-level metabolic signature.

The Alzheimer’s group showed a two-sided metabolic shift: glucose activity was higher in both visceral and subcutaneous fat, while metabolic load scores were lower in several major brain networks. Compared with cognitively normal participants, patients had reduced expression of the DMN, dorsal attention network, frontoparietal network and sensorimotor network. The investigators also calculated a measure called the default-mode-network-centered metabolic expression concordance index, or DMN-MEC. This index describes how closely the relative metabolic expression of the DMN is coordinated with that of other large-scale networks within an individual brain. Patients with Alzheimer’s disease had a lower global DMN-MEC, indicating that the usual relationships among these systems were less coherent. Rather than simply showing reduced activity in one region, the pattern points to a breakdown in the metabolic coordination that allows distributed brain networks to operate as an integrated system.

Within the Alzheimer’s group, the relationships were especially pronounced for visceral fat. Higher visceral adipose tissue metabolism was significantly associated with a lower global DMN-MEC index, whereas metabolism in subcutaneous fat showed no comparable association. Greater visceral fat activity was also linked to lower scores on the Mini-Mental State Examination and the Montreal Cognitive Assessment, two widely used screening tools for global cognitive function. In contrast, stronger DMN metabolic load and higher global DMN-MEC were associated with better cognitive performance. The pattern is consistent with the idea that the DMN acts as a central organizing system whose metabolic coordination with other networks may deteriorate alongside cognitive decline. It also suggests that the metabolic state of deep abdominal fat may capture information about this disruption that is not apparent from subcutaneous fat measurements alone.

The study’s design provides a possible biological explanation for the association, although the researchers did not directly test the underlying molecular pathways. Visceral fat can release inflammatory cytokines and other adipose-derived factors, alter insulin signaling and increase the flow of circulating fatty acids. Insulin resistance may be particularly relevant because insulin regulates glucose handling in many tissues, including the brain, and impaired insulin signaling has been implicated in pathways involving amyloid-beta and tau, the proteins most closely associated with Alzheimer’s pathology. Inflammation can affect endothelial cells and weaken the blood–brain barrier, potentially changing the brain’s exposure to circulating signals. These mechanisms could influence neuronal energy use and the synchronization of network-level metabolism. However, the PET findings alone cannot determine whether visceral fat dysfunction precedes brain-network disruption, results from it or reflects a third process such as systemic metabolic disease.

The investigators emphasize that their results should not be interpreted as proof that abdominal fat directly causes Alzheimer’s disease or that reducing visceral fat will prevent cognitive decline. The analysis was observational and focused on people who already had Alzheimer’s disease, so it cannot establish temporal sequence or treatment effects. The abstract also does not report detailed information about participants’ body mass index, diabetes status, medication use, disease severity or the distribution of Alzheimer’s pathology, factors that could influence both adipose-tissue glucose uptake and brain metabolism. In addition, PET measures glucose uptake indirectly and cannot by themselves identify which cell types or biochemical pathways are responsible for the signal. Nevertheless, the use of total-body imaging gives the study a distinctive strength: it measures metabolic activity in the brain and abdominal tissues during the same investigation, making it possible to examine the brain–fat relationship at the level of whole-body physiology.

The findings could help shape future biomarker research by combining peripheral metabolism with network-based neuroimaging. A blood test or abdominal imaging measure that reflects visceral fat dysfunction might eventually complement established markers of amyloid and tau, particularly if it predicts changes in brain-network integrity before noticeable symptoms appear. Longitudinal studies will be needed to determine whether elevated visceral fat metabolism predicts later cognitive deterioration, whether it changes as Alzheimer’s progresses and whether lifestyle or metabolic interventions alter the DMN-MEC signature. Researchers may also be able to test whether inflammatory markers, insulin sensitivity, circulating lipids or adipose-derived hormones mediate the association. For now, the study adds evidence to a rapidly expanding picture of Alzheimer’s disease in which the brain is metabolically connected to the rest of the body—and in which the fat surrounding internal organs may provide an unexpectedly informative window into the failure of cognitive networks.