The claim

“Cold exposure improves insulin sensitivity by 43%.”

Stretched. The 43% came from eight men with type 2 diabetes who spent about six hours a day in 14–15°C air for ten days. When the same group repeated it at 16–17°C and kept people from shivering, insulin sensitivity didn't improve.

Updated Sep 24, 2026 · 2 studies reviewed

A real finding has been pulled well past what the study showed.

People say it in places like these

Podcasts
Cold exposure improves insulin sensitivity by 43 percent, so plunging helps control blood sugar.
Wellness sites
Ten days of cold raised insulin sensitivity by almost half in people with diabetes.

The research found this

The number comes from a 2015 study in Nature Medicine. Eight patients with type 2 diabetes spent ten days in mild cold. They sat in shorts and a T-shirt in a room whose air and walls were held at 14–15°C.Source 1 · Clinical trialShort-term cold acclimation improves insulin sensitivity in patients with type 2 diabetes mellitusHanssen MJW, Hoeks J, Brans B, et al.. Nature Medicine, 2015.Read the paper ↗PubMed ↗ The group's conference abstract describes about six hours a day and calls the patients overweight or obese men around 59 years old. Peripheral insulin sensitivity rose about 43%.

Most of the change came from muscle. Glucose transporters called GLUT4 moved to the surface of muscle cells in much greater numbers, while brown fat took up only slightly more glucose.Source 1 · Clinical trialShort-term cold acclimation improves insulin sensitivity in patients with type 2 diabetes mellitusHanssen MJW, Hoeks J, Brans B, et al.. Nature Medicine, 2015.Read the paper ↗PubMed ↗ Insulin signaling itself didn't change, and the authors credited the muscle changes for most of the effect.

Six years later the same group ran a milder version with nine patients and avoided overt shivering. The room averaged 16.4°C, which was about 1.4°C warmer than before, and insulin sensitivity didn't improve.Source 2 · Clinical trialMetabolic responses to mild cold acclimation in type 2 diabetes patientsRemie CME, Moonen MPB, Roumans KHM, et al.. Nature Communications, 2021.Read the paper ↗PubMed ↗ Liver fat and the after-meal levels of glucose and lipids stayed the same. With far less shivering reported than in the first study, the authors proposed that some muscle contraction is needed.

A 2024 study leaned into shivering. Fifteen adults with overweight or obesity were cooled enough to shiver for an hour a day for ten days, and their oral glucose tolerance improved.Source 3 · Clinical trialCold acclimation with shivering improves metabolic health in adults with overweight or obesitySellers AJ, van Beek SMM, Hashim D, et al.. Nature Metabolism, 2024.Read the paper ↗PubMed ↗ Fasting glucose, triglycerides, free fatty acids and blood pressure improved as well. The abstract doesn't give the size of these changes, and the study had no control group.

The dial reads 62°H for four reasons

How the reading adds up

12 + 16 + 14 + 20 = 62°H

EvidenceWhat kind of evidence exists in people?
12/25
The result comes from eight patients tested with a glucose clamp before and after ten days of cold, and there was no control group.Source 1 · Clinical trialShort-term cold acclimation improves insulin sensitivity in patients with type 2 diabetes mellitusHanssen MJW, Hoeks J, Brans B, et al.. Nature Medicine, 2015.Read the paper ↗PubMed ↗ None of the insulin studies ran longer than ten days.Source 2 · Clinical trialMetabolic responses to mild cold acclimation in type 2 diabetes patientsRemie CME, Moonen MPB, Roumans KHM, et al.. Nature Communications, 2021.Read the paper ↗PubMed ↗Source 3 · Clinical trialCold acclimation with shivering improves metabolic health in adults with overweight or obesitySellers AJ, van Beek SMM, Hashim D, et al.. Nature Metabolism, 2024.Read the paper ↗PubMed ↗
ConsistencyHas the finding held up?
16/25
The same Dutch group tried again at 16–17°C with shivering avoided, and insulin sensitivity didn't improve in nine patients.Source 2 · Clinical trialMetabolic responses to mild cold acclimation in type 2 diabetes patientsRemie CME, Moonen MPB, Roumans KHM, et al.. Nature Communications, 2021.Read the paper ↗PubMed ↗ A 2024 study that made people shiver for an hour a day found better glucose tolerance, and the authors of the failed repeat proposed that some muscle contraction is needed.Source 3 · Clinical trialCold acclimation with shivering improves metabolic health in adults with overweight or obesitySellers AJ, van Beek SMM, Hashim D, et al.. Nature Metabolism, 2024.Read the paper ↗PubMed ↗Source 2 · Clinical trialMetabolic responses to mild cold acclimation in type 2 diabetes patientsRemie CME, Moonen MPB, Roumans KHM, et al.. Nature Communications, 2021.Read the paper ↗PubMed ↗
MagnitudeDoes the claim match the size of the effect?
14/25
The 43% is the measured change in peripheral insulin sensitivity in eight men with type 2 diabetes.Source 1 · Clinical trialShort-term cold acclimation improves insulin sensitivity in patients with type 2 diabetes mellitusHanssen MJW, Hoeks J, Brans B, et al.. Nature Medicine, 2015.Read the paper ↗PubMed ↗ The claim applies it to cold exposure in general and leaves out the failed repeat.Source 2 · Clinical trialMetabolic responses to mild cold acclimation in type 2 diabetes patientsRemie CME, Moonen MPB, Roumans KHM, et al.. Nature Communications, 2021.Read the paper ↗PubMed ↗
DoseDoes the studied protocol match how people use it?
20/25
The men sat in 14–15°C air in shorts and a T-shirt for about six hours a day, and over ten days that adds up to roughly 54–60 hours of cold.Source 1 · Clinical trialShort-term cold acclimation improves insulin sensitivity in patients with type 2 diabetes mellitusHanssen MJW, Hoeks J, Brans B, et al.. Nature Medicine, 2015.Read the paper ↗PubMed ↗ Both studies that measured insulin sensitivity used cold room air.Source 1 · Clinical trialShort-term cold acclimation improves insulin sensitivity in patients with type 2 diabetes mellitusHanssen MJW, Hoeks J, Brans B, et al.. Nature Medicine, 2015.Read the paper ↗PubMed ↗Source 2 · Clinical trialMetabolic responses to mild cold acclimation in type 2 diabetes patientsRemie CME, Moonen MPB, Roumans KHM, et al.. Nature Communications, 2021.Read the paper ↗PubMed ↗

The claim drifts from the data here

The claim turns a ten-day lab protocol into a property of cold itself. The 43% needed about six hours a day of 14–15°C air, and a slightly warmer version without shivering produced no gain.Source 1 · Clinical trialShort-term cold acclimation improves insulin sensitivity in patients with type 2 diabetes mellitusHanssen MJW, Hoeks J, Brans B, et al.. Nature Medicine, 2015.Read the paper ↗PubMed ↗Source 2 · Clinical trialMetabolic responses to mild cold acclimation in type 2 diabetes patientsRemie CME, Moonen MPB, Roumans KHM, et al.. Nature Communications, 2021.Read the paper ↗PubMed ↗

It also leaves out who took part. All eight had type 2 diabetes, and none of the studies tested a short plunge.Source 1 · Clinical trialShort-term cold acclimation improves insulin sensitivity in patients with type 2 diabetes mellitusHanssen MJW, Hoeks J, Brans B, et al.. Nature Medicine, 2015.Read the paper ↗PubMed ↗ The sauna side of the question has its own page.

Put it to use

If blood sugar is your reason to try cold, know that the benefit showed up after hours of daily cold air in a lab, and the studies point to shivering as part of it.Source 1 · Clinical trialShort-term cold acclimation improves insulin sensitivity in patients with type 2 diabetes mellitusHanssen MJW, Hoeks J, Brans B, et al.. Nature Medicine, 2015.Read the paper ↗PubMed ↗Source 3 · Clinical trialCold acclimation with shivering improves metabolic health in adults with overweight or obesitySellers AJ, van Beek SMM, Hashim D, et al.. Nature Metabolism, 2024.Read the paper ↗PubMed ↗ Nobody has tested a plunge routine for insulin sensitivity.

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Check these claims next

72°H

Stretched

Cold

“Cold plunges burn fat by switching on brown fat.”

Cold does switch on brown fat in people. The one controlled study that measured fat used two hours of 17°C air a day for six weeks and took off 0.7 kg of fat, and nobody has measured fat loss from plunges.

80°H

Hot air

Heat

“Sauna improves your blood sugar control.”

The only sauna trial with a glucose test found blood sugar rose more after a session. Small hot-tub trials lowered fasting glucose, and a review of randomized heating trials found no effect on fasting glucose or HbA1c.

89°H

Hot air

Cold

“Eleven minutes of cold a week is the ideal dose.”

A 2021 paper added up the cold-water habits that seven Danish winter swimmers reported and got 11 minutes a week. The study never assigned or compared a dose, and its lab cold came from water-perfused blankets.

We cited these sources

01Hanssen MJW, Hoeks J, Brans B, van der Lans AAJJ, Schaart G, van den Driessche JJ, et al.. Short-term cold acclimation improves insulin sensitivity in patients with type 2 diabetes mellitus. Nature Medicine. 2015;21(8):863-865. doi:10.1038/nm.3891 PMID 26147760
02Remie CME, Moonen MPB, Roumans KHM, Nascimento EBM, Gemmink A, Havekes B, et al.. Metabolic responses to mild cold acclimation in type 2 diabetes patients. Nature Communications. 2021;12(1):1516. doi:10.1038/s41467-021-21813-0 PMID 33750795
03Sellers AJ, van Beek SMM, Hashim D, Baak R, Pallubinsky H, Moonen-Kornips E, et al.. Cold acclimation with shivering improves metabolic health in adults with overweight or obesity. Nature Metabolism. 2024;6(12):2246-2253. doi:10.1038/s42255-024-01172-y PMID 39643644

People say it in places like these

The research found this

The dial reads 62°H for four reasons

EvidenceWhat kind of evidence exists in people?

ConsistencyHas the finding held up?

MagnitudeDoes the claim match the size of the effect?

DoseDoes the studied protocol match how people use it?