# Distinct associations between body mass index and polyunsaturated fatty acids in dementia with Lewy Bodies and Alzheimer’s disease

## TL;DR

This study found that body mass index is linked to specific fatty acid changes in dementia with Lewy bodies but not in Alzheimer's disease.

## Contribution

The study reveals distinct metabolic associations between BMI and PUFA in dementia subtypes, offering insights for personalized nutrition.

## Key findings

- DLB patients showed positive BMI associations with downstream omega-6 PUFAs like GLA, AA, and adrenic acid.
- BMI in DLB was linked to increased desaturase and elongase activity, indicating higher fatty acid turnover.
- No significant BMI-PUFA associations were found in Alzheimer's disease patients.

## Abstract

We aimed to assess the association between body mass index and polyunsaturated fatty acids to determine potential links and metabolic differences between Alzheimer's disease and dementia with Lewy bodies.

We performed a cross-sectional study of enrolment data with 133 patients with mild AD (n = 75) and DLB (n = 58) from a Norwegian cohort study. We used linear regression models adjusting for age, sex, and diagnosis to explore the association between PUFA concentrations and BMI estimates.

In DLB patients, BMI was positively associated with downstream omega-6 PUFA, including gamma-linolenic acid (GLA; β = 0.285, p = 0.012), arachidonic acid (AA; β = 0.320, p = 0.005), and adrenic acid (β = 0.303, p = 0.005). BMI was also related to increased Δ6-desaturase n-6 activity (β = 0.383, p = 0.002) and Δ6-desaturase n-3 activity (β = 0.335, p = 0.011), along with reduced elongase n-6 (β = –0.396, p = 0.002) and elongase n-3 (β = –0.376, p = 0.004), suggesting increased fatty acid turnover. No significant associations were found in the AD group.

BMI in DLB patients was positively associated with elevated downstream omega-6 metabolites and desaturase and elongase activity, compatible with higher fatty‑acid turnover and systemic inflammatory state hypothesized in DLB. These findings highlight the distinct metabolic alterations across dementia subtypes that are relevant for personalized nutritional strategies in dementia care.