A new study published in the journal “Brain, Behavior, and Immunity” shows that adolescent rats that consume a diet high in saturated fats have a harder time coping with stress as adults.
Researchers from Loma Linda University in California found that the areas of the brain that handle the fear/stress response were altered to the point that subjects began exhibiting behaviors that mirror post-traumatic stress disorder (PTSD).
“The teen years are a very critical time for brain maturation, including how well (or not) we'll cope with stress as adults," said Johnny Figueroa, assistant professor in the Division of Physiology, Department of Basic Sciences and Center for Health Disparities and Molecular Medicine at Loma Linda UniversitySchool of Medicine. “The findings of our research support that the lifestyle decisions made during adolescence—even those as simple as your diet—can make a big difference in our ability to overcome everyday challenges.”
In the study, “Exposure to an Obesogenic Diet During Adolescence Leads to Abnormal Maturation of Neural and Behavioral Substrates Underpinning Fear and Anxiety,” researchers investigated the impact of an obesogenic (tending to cause obesity), Western-style high-saturated-fat diet on the development of brain areas involved in responding to fear and stress.
Study findings demonstrate that the consumption of an obesogenic diet during adolescence has a profound effect on various components of fear in the adult rat. Notably, the rats that consumed the high-saturated-fat diet exhibited more anxiety, more problems with learning processes, and an impaired fear-startle response.
Startle reflexes, which are studied in humans and lab animals, play a prominent role in anxiety and PTSD research. In this study, consumption of an obesogenic diet during adolescence reduced the rats’ extinction of fear memories—a major impairment also observed in people suffering from PTSD.
In addition to not properly learning fear associations, the rats on the high-saturated-fat diet incorrectly assessed the level of threat. This suggests that obesity and the associated metabolic alterations may predispose individuals to PTSD-related mental illness.
Researchers reported that the animals in the high-saturated-fat diet group exhibited alterations in the structure of brain regions associated with PTSD, including the amygdala and the prefrontal cortex. Notably, the group found that the left-brain hemisphere seems to be more vulnerable to the effects of high saturated-fat consumption and obesity-related metabolic alterations. Understanding the neural networks that predispose obese adolescents to develop anxiety and stress-related disorders may help target metabolic measures to alleviate the burden of mental illness in this growing population.
Increases in obesity disproportionately affect children from low socioeconomic status, Figueroa said. “While obesity prevalence increased by 10 percent for all US children, it increased by 23–33 percent for children of low socioeconomic status.”
Figueroa said the study leaves other questions open for further investigation, such as replicability in human subjects and whether the alterations seen in the brain structures are permanent or the effects can be reversed.
Study limitations include lack of clarity on how the high-saturated-fat diet affects the adult brain, and whether the effects of the obesogenic diet on the fear response are related to deficits in fear memory consolidation, retrieval, and expression.
“Obesity imposes a major risk for adverse mental outcomes and may contribute to the impact of low socioeconomic status on neurocognitive performance, academic achievement, and social integration,” Figueroa said. “Thus, understanding how obesity influences the maturing brain is integral to improve minority mental health.”