One hour of daily cold exposure with shivering for 10 days enhances glucose tolerance and metabolic health in individuals with overweight or obesity.
goosebumpsStudy:Cold-induced shivering for metabolic health. Image Credit: Tunatura/Shutterstock.com
In a recent study published in Nature Metabolism, researchers investigated the effects of shivering due to cold on metabolic health in people with obesity and overweight.
They found that exposing people to cold for an hour for 10 days can improve their tolerance to glucose and lead to other benefits for metabolic health.
Background
Studies suggest that acclimation to cold can improve sensitivity to insulin in type 2 diabetes. Still, these benefits are not felt if shivering is prevented, indicating that shivering is instrumental to maximizing the metabolic benefits of cold exposure.
About the study
This study investigated the lasting effects of exposure to cold, specifically when the response included shivering, on glucose metabolism by assessing its impact on tolerance to oral glucose in a sample of 15 obese or overweight adults, including 9 participants who were intolerant to glucose.
The study participants were White individuals of Western European descent, including four post-menopausal women. They ranged in age from 40 to 75 years and had a body mass index (BMI) between 27 and 35.
The intervention involved 10 days of cold acclimation, with participants exposed to cold for 1 hour each day to induce shivering. The primary outcome was the total glucose area under the curve (AUC) measured by using an oral glucose tolerance test (OGTT).
Metabolic assessments were conducted at thermoneutrality before the intervention, after the first cold exposure, and after the 10-day cold acclimation period. Additionally, various metabolic markers, such as fasting plasma glucose, triglycerides, and non-esterified fatty acids (NEFA) were measured.
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Energy expenditure was monitored during cold exposure, and shivering was confirmed using electromyography in six monitored muscles. Fat mass, fat-free mass, and serum creatine kinase levels were also measured as secondary outcomes.
The study also assessed changes in skeletal muscle gene expression through RNA sequencing and examined markers related to glucose transport (GLUT4) and glycogen concentration. To assess cardiovascular effects, blood pressure was measured before and after the intervention.
Throughout the study, data on changes in body composition, energy expenditure, and other metabolic factors were recorded to understand the broader effects of cold exposure on metabolic health.
Findings
The findings showed that 10 days of cold exposure with shivering led to significant improvements in glucose metabolism. After acclimation to cold, the glucose AUC at the time of OGTT was 6% lower, and fasting plasma glucose levels decreased by 3%.
Additionally, the 2-hour glucose concentration was reduced by 11%, indicating improved glucose tolerance. Among participants who were initially glucose intolerant, the number of individuals with impaired glucose tolerance decreased after the intervention.
Cold acclimation also had positive effects on lipid metabolism, including a 14% reduction in the NEFA AUC and a 32% reduction in fasting triglycerides. This suggests that cold exposure with shivering can improve glucose and lipid homeostasis.
Beyond metabolic effects, acclimation to cold also reduced blood pressure, with a ten mmHg decrease in systolic and a seven mmHg decrease in diastolic blood pressure observed in each participant. These effects were noted after a single period of exposure to cold, but they were more pronounced after 10 days.
Interestingly, cold acclimation did not significantly alter muscle glycogen levels or GLUT4 content. Still, it did upregulate genes related to extracellular matrix remodeling in the skeletal muscle, suggesting that there may be structural adaptations at play.
Conclusions
This study emphasizes the importance of shivering in mediating the metabolic and cardiovascular benefits of cold exposure, highlighting its potential for improving insulin sensitivity, lipid metabolism, and blood pressure.
The study has several limitations: a single arm was included in the research design instead of a randomized controlled trial with a clear comparison group, so researchers were unable to establish causality.
Nor could researchers fully adjust for lifestyle factors as participants were free to leave the study site. Variations in duration of exposure to cold, energy expenditure, and shivering intensity may have affected the results. Additionally, the OGTT might have masked some metabolic effects due to its impact on muscle blood flow.
Finally, while the contribution of brown adipose tissue to the observed improvements is considered minor, researchers could not fully rule it out as a possible cause.
Despite these limitations, the study suggests acclimation to cold with shivering may help prevent cardiovascular disease and type 2 diabetes.
Further studies with longer durations or higher intensity cold exposure may further amplify these effects, while the inclusion of more diverse samples will make findings more generalizable to broader populations.
Journal reference:
Sellers, A.J., van Beek, S.M.M., Hashim, D., Baak, R., Pallubinsky, H., Moonen-Kornips, E., Schaart, G., Gemmink, A., Jörgensen, J.A., van de Weijer, T., Kalkhoven, E., Hooiveld, G.J., Kersten, S., Hesselink, M.K.C., Schrauwen, P., Hoeks, J., van Marken Lichtenbelt, W.D. (2024) Cold acclimation with shivering improves metabolic health in adults with overweight or obesity. Nature Metabolism. doi:10.1038/s42255-024-01172-y. https://www.nature.com/articles/s42255-024-01172-y