Is Obesity Associated With a Decline in Intelligence Quotient During the First Half of the Life Course?
MedicalResearch.com: What are the main findings of the study?
Dr. Belsky: Midlife obesity is linked with increased risk for dementia later in life. Recently, studies have reported that obese children and teens also have lower IQs. These studies have led scientists to speculate that obesity may harm the brain already in early life. We followed a cohort of 1000 children from birth through midlife (age 38 years) to understand how becoming obese might affect intellectual functioning.
We measured children’s IQs when they were ages 7-11. We measured the IQs of those same children three decades later (at age 38).
We found that, as expected, the children who became obesity between age 11 and age 38 years had lower IQs. But they had lower IQs already at age 11, before they became obese. We found no evidence that developing obesity contributed to decline in IQ from childhood to adulthood. This remained true when we accounted for childhood obesity preceding the first IQ measurement and when we focused on cases who developed severe obesity, with metabolic and or inflammatory abnormalities.
MedicalResearch.com: Were any of the findings unexpected?
Dr. Belsky: These findings were not unexpected–previous longitudinal studies have shown that children with low IQs are at increased risk for obesity--but they do call for new consideration of findings linking obesity with cognitive decline. Low childhood IQ is a risk factor for both midlife obesity and late-life dementia. Therefore, studies linking obesity with dementia may need to consider premorbid IQ lest they overestimate the effects of obesity on cognitive decline.
MedicalResearch.com: What should clinicians and patients take away from your report?
Dr. Belsky: Obesity is unlikely to damage the brain during the first half of the life course.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Dr. Belsky: Future studies should investigate whether associations between midlife obesity and later life cognitive decline can be explained by premorbid differences in IQ between obese cases and lean controls.