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A new study has shown that obesity may not be linked to diet alone, as a disruption in the body's daily rhythm of stress hormones can contribute to weight gain and alter how the body handles fat and insulin.
The study explained that the underlying cause of obesity may affect how the body processes fat and insulin, meaning that obesity resulting from hormonal disruption may differ in its characteristics from that associated with consuming a high-fat diet.
Researchers at Weill Cornell Medicine conducted experiments on mice, comparing the effects of a high-fat diet with the impact of disrupting the daily rhythm of glucocorticoid hormones—hormones that help the body regulate its stress response, in addition to playing a role in a number of metabolic processes.
The results showed that mice exposed to hormonal rhythm disruption developed obesity despite not eating a high-fat diet, but they stored fat differently than mice that became obese due to diet.
In mice with the hormonal disruption, fat was distributed more in adipose tissue, while the liver remained less susceptible to fat accumulation. In contrast, a high-fat diet led to greater overall body fat accumulation and was more clearly associated with liver fat.
When a high-fat diet was combined with hormonal rhythm disruption, the mice recorded the highest levels of fat accumulation.
Researchers also observed a difference in how insulin resistance manifests. In mice exposed to hormonal rhythm disruption, insulin resistance was primarily concentrated in the muscles, while adipose tissue remained able to respond to insulin and store fat.
This pattern may help limit the transfer of fat to the liver and its accumulation there, which distinguishes this type of obesity from obesity linked to a high-fat diet.
These findings support a previous study conducted by the same research team in 2022, which showed that disrupting the daily rhythm of glucocorticoid hormones can lead to a significant increase in fat in mice without an increase in their food intake.
These findings gain special significance in light of studies conducted on humans linking disruptions in the daily rhythm of the cortisol hormone to obesity, and changes in this rhythm have also been observed in people suffering from chronic stress or working shift jobs.
Dr. Mary Teruel, who led the study, stated that the results indicate obesity may not be a single condition resulting from a single cause, explaining that insulin resistance may vary from one tissue to another depending on the triggering factor.
The study indicates that understanding obesity may require looking beyond diet and calories to factors including sleep disruption, stress, and the timing of hormonal signals.
However, the researchers emphasize that further studies are needed to determine the extent to which these findings apply to humans, and whether hormonal rhythm disruption could represent an independent pathway for developing obesity and its complications.
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