Higher body weight was not found to be associated with smaller hippocampal volume in adolescents but may be associated with lower T2-weighted signal intensity, suggesting lipid accumulation within the hippocampus, according to study results published in Obesity.

One of the main structures involved in food intake and weight regulation is the hippocampus, and previous studies have reported that obesity is associated with smaller hippocampal volumes. Obesity has also been associated with increased T2-weighted signal intensity in the hypothalamus, indicative of gliosis, but there are no data on changes in T2-weighted signal intensity within the hippocampus in relation to obesity.

The goal of the current study was to investigate body weight-associated changes in hippocampal volume and tissue signal intensity in adolescents.

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The study included 102 adolescents aged 12 to 18 years (mean age, 15.07 years) with available structural magnetic resonance imaging and anthropometric data from the Pediatric Imaging, Neurocognition, and Genetics (PING) Project. Three PING sites provided the required information: Honolulu, Hawaii; New Haven, Connecticut; and New York, New York.

Most adolescents (65%) had body mass index (BMI) in the healthy-weight category (5th to 84th percentile), 13% had BMI in the overweight category (85th to 95th percentile), 19% had BMI in the obesity category (>95th percentile), and 4% had BMI in the underweight category (<5th percentile). The researchers used the Centers for Disease Control and Prevention growth charts to calculate standardized BMI scores (BMIz).

Linear models including multiple covariates, such as age, sex, site, parental income, and total intracranial volume, did not reveal a significant association between BMIz and bilateral hippocampal, amygdala, or nucleus accumbens volumes. However, statistical analysis revealed a negative association between BMIz and left (t =-3.26; P =.002) and right (t =-2.57; P =.01) hippocampal signal intensity.

The researchers acknowledged several study limitations, including the cross-sectional design, limited sample size, potential unmeasured variables, missing dietary information, and lack of a formal measure of puberty.

“Our results provide important information that will improve our understanding of the association between weight and neural structures, and they will contribute to prevention programs during a critical brain development period,” concluded the researchers.

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Mestre Z, Bischoff-Grethe A, Wierenga CE, et al. Associations between body weight, hippocampal volume, and tissue signal intensity in 12- to 18-year-olds [published online June 5, 2020]. Obesity (Silver Spring). doi:10.1002/oby.22841