BLOG

“Obesity is linked to heart disease, stroke, type 2 diabetes, metabolic syndrome and certain cancers, which are among the leading causes of preventable, premature death.”

Obesity has become a global epidemic, with significant health and economic impacts. In 2022, approximately 2.5 billion adults worldwide, aged 18 and older were classified as overweight, with over 890 million of them living with obesity. This represents 43% of the adult population worldwide. According to the CDC comparable statistics for the United States are: two-thirds of adults are overweight, including obese. This includes 35 million men and 35 million women (40% of adults) who are obese, and 45 million women and 54 million men (32% of adults) who are overweight. 

The annual medical costs attributable to obesity in the US reached nearly $173 billion in 2019, with obese individuals incurring $1,861 more in medical expenses compared to their healthy-weight counterparts. Alarmingly, projections suggest that by 2030, nearly half of all U.S. adults will be obese, underscoring the urgent need for effective interventions and preventative measures. Obesity is linked to numerous serious health conditions, including heart disease, stroke, type 2 diabetes, and certain cancers, which are among the leading causes of preventable, premature death.

Various factors, including genetic predisposition, lifestyle and diet, and environmental factors, influence obesity. Among these, early life adversity (ELA) plays an role in predisposing individuals to obesity and related disorders such as food addiction. ELA includes various forms of childhood trauma, including physical and emotional abuse, neglect, and family conflict. These adversities can lead to long-lasting structural and functional brain alterations, specifically in reward processing and emotional regulation areas.

“Among these, ELA plays an important role in predisposing individuals to obesity and related disorders such as food addiction.”

Neuroimaging studies have shown that obesity is associated with distinct differences in the brain’s resting state activity, the activity of nerve networks in the absence of any tasks or stimuli. Specifically, there is often an imbalance between the homeostatic and reward aspects of ingestive behavior, which can contribute to the development of food addiction. Homeostatic aspects of ingestive behavior refer to assuring the food intake necessary to fulfill the needs of the body and brain to keep functioning properly, reward or hedonic aspects refer to the aspects of eating behavior related to generate pleasure.

In a study conducted by Dr. V. Osadchiy, MD from the UCLA David Geffen School of Medicine, and G. Oppenheimer Center for Neurobiology of Stress and Resilience at UCLA, a team of investigators aimed to explore the interactions between ELA, brain connectivity, and food addiction and to determine sex-specific differences in these associations in obese individuals. This research, published in the 2019 edition of Obesity Science and Practice journal, recruited 186 right-handed participants from UCLA and the local community. Participants were categorized based on their body mass index (BMI) into two groups: those with high BMI (≥25) and those with normal BMI (18.50–24.99). The high BMI group included 54 men and 53 women, while the normal BMI group comprised 30 men and 49 women.

Early life adversity was assessed using the Early Traumatic Inventory – Self Report (ETI-SR), which measures childhood traumatic and adverse life events across four domains: general trauma, physical punishment, emotional abuse, and sexual abuse. Food addiction was assessed using the Yale Food Addiction Scale (YFAS), which is based on criteria from the DSM-IV and DSM-V. Brain imaging data were analyzed to identify several brain networks, focusing on the connectivity between regions involved in reward, emotion regulation, salience, executive control, and somatosensory functions.

Participants with high BMI had higher ETI-SR scores, specifically in the general, emotional, and total categories, than those with normal BMI. Although group differences in YFAS scores did not reach statistical significance, individuals with high BMI generally noted higher food addiction scores.

“Participants with high BMI demonstrated significant associations between ELA and the centrality of brain regions involved in reward and emotion regulation.”

Centrality refers to the influence of a particular brain region within a network of connected brain regions, in other words, the higher the centrality of a brain region, the more it is able to influence the activity in other brain regions of a network. Specifically, increased ELA was linked to higher centrality in regions such as the basal ganglia (involved in movement and reward processing) and amygdala (key in processing emotions and fear responses) in women, while men showed associations with somatosensory regions (areas involved in processing sensory information such as touch).

In the high BMI group, higher food addiction scores were associated with decreased centrality in the thalamus (a central relay station for sensory and motor signals) and increased centrality in the ventral tegmental area/substantia nigra (VTA–SN, crucial for reward and movement regulation). These associations were sex-specific, with women showing positive relationships between food addiction and centrality in reward regions, whereas men showed negative associations with these same regions. It is important to note that the study was correlational, meaning it identified associations between ELA, brain connectivity, and obesity but did not establish direct cause-and-effect relationships​​.

“In response to ELA, women with high BMI showed increased centrality in reward and emotion regulation regions, while men showed changes in somatosensory regions.”

The findings of this study imply that ELA can lead to long-term alterations in brain connectivity, particularly in regions involved in reward processing and emotional regulation. These changes are sex-specific and may contribute to the development of food addiction and obesity later in life. In response to ELA, women with high BMI showed increased centrality in reward and emotion regulation regions, while men showed changes in somatosensory regions.

The study highlights the importance of considering sex differences and the role of early life adversity in understanding the neurobiological mechanisms underlying obesity and food addiction. The results stress the need for a holistic approach that considers sex-specific differences in the treatment and prevention of obesity, especially in individuals with a history of childhood trauma.