In a new study, researchers found that changes in chemical rhythms may cause eating behaviors that lead to obesity.
The finding helps to untangle how part of the nervous system changes in adults affected by obesity, and what role this plays in appetite, eating behaviors, and even sleep cycles.
The research was conducted by a team at the University of Chicago.
Obesity is a common health problem affecting over 90 million adults in the United States.
However, how different chemical signals in the body respond to this disease continues to remain unclear.
The endocannabinoid system is a part of the nervous system that helps to regulate many processes in the body including appetite, pain and the immune system.
It is involved in hedonic eating or eating for reward purposes.
Previously, the team had shown that a chemical signal in the endocannabinoid system known as 2-AG follows a cycle where its levels in the blood are low overnight, and then rise during the day to peak in the mid-afternoon.
They thought obese people would have an overactive endocannabinoid system (measured by increased 2-AG levels) compared to lean individuals.
However, the research into this area has shown mixed results; the question remains as to how 2-AG levels relate to obesity.
In the study, the team wanted to look further and try to answer how 2-AG levels may change in obese adults compared with non-obese people.
They recruited a mix of non-obese and obese adults to participate in the study.
The researchers then monitored their blood levels of 2-AG, cortisol, a marker of central circadian timing, and leptin, a molecule known to signal fullness from eating.
They found that the rhythmic cycle of 2-AG levels, from low overnight to a mid-afternoon peak, was delayed.
The low and high points were dampened too, with less extreme high and low points in the cycle. This delay and change in the cycle led to higher levels of 2-AG in the evening for obese people, which may mean that the urge for hedonic feeding (or eating for pleasure) is stronger later in the day for obese individuals, a quality previously linked to weight gain.
The team says future work will test if habitually the obese individuals ate more later in the day, or if this 2-AG rhythm drives them to eat later in the day.
The lead author of the study is Erin Hanlon, Ph.D., a research assistant professor in the section of endocrinology, diabetes, and metabolism.
The study is published in the Journal of Clinical Endocrinology and Metabolism.
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