The most compelling evidence linking cold exposure to metabolic health doesn’t come from the wellness world. It comes from a diabetes laboratory in Maastricht, the Netherlands, and it was published in Nature Medicine, one of the most rigorous medical journals on earth.
In 2015, a team led by Patrick Schrauwen, a Minkowski Prize–winning metabolic researcher at Maastricht University, exposed eight patients with type 2 diabetes to ten days of mild cold acclimation. Their result: a 43% improvement in peripheral insulin sensitivity. To put that in context, some diabetes medications struggle to deliver numbers that large. And with 589 million adults currently living with diabetes worldwide and another 635 million estimated to have impaired glucose tolerance, even a modest complementary intervention could matter at population scale.
But the finding that makes this study important for anyone investigating cold plunge insulin sensitivity isn’t the headline figure. It’s what was happening inside the body. The improvement wasn’t driven by brown fat, the tissue that dominates cold therapy marketing. It was driven by skeletal muscle. And a follow-up study from the same laboratory found that when they prevented participants from shivering, the metabolic benefit vanished completely.
That combination of a dramatic clinical result, a surprising mechanism, and an honest boundary condition makes this one of the most interesting and most misunderstood areas in metabolic health research. It deserves to be read carefully rather than selectively.
The centrepiece: ten days of cold, 43% insulin sensitivity improvement
The Hanssen study remains the single strongest piece of evidence linking cold exposure to blood sugar regulation in people with type 2 diabetes.
Eight patients with T2D spent ten consecutive days in a cold-acclimated room set to 14–15°C (roughly 57–59°F) for six hours each day. They wore standard hospital clothing. They didn’t exercise, didn’t change their diets, and continued any existing medications. The only intervention was sustained mild cold.
Before and after the ten-day protocol, the team measured insulin sensitivity using the gold-standard hyperinsulinaemic-euglycaemic clamp, a technique that directly quantifies how effectively the body clears glucose from the blood when insulin is present. After ten days, glucose disposal had increased by 43%.
Journal prestige matters here. Nature Medicine has an acceptance rate of roughly 7% and publishes only findings considered to have significant clinical implications. For a small cold exposure study to clear that bar signals that the editors and reviewers considered both the mechanism and the metabolic effect noteworthy.
Real limitations should be stated plainly. Eight participants is a small sample. There was no control group; each patient served as their own control, measured before and after. And the protocol involved six hours per day of sustained cold, a very different proposition from a five-minute ice bath. None of that erases the finding. But it frames it correctly: a striking signal from a top-tier journal, demanding replication and extension rather than uncritical adoption.
The mechanism nobody talks about
Ask most cold therapy enthusiasts why cold exposure affects blood sugar, and the answer will involve brown adipose tissue. Brown fat burns calories. Brown fat consumes glucose. Brown fat is activated by cold. The story is simple, shareable, and partially true.
A 2014 study by Chondronikola and colleagues published in Diabetes, the American Diabetes Association’s journal, demonstrated that prolonged cold exposure improved glucose disposal and insulin sensitivity in men who had measurable brown fat deposits, but not in men who lacked them. Brown fat does participate in glucose metabolism during cold. But the Hanssen study revealed it was a supporting player, not the lead.
Hanssen’s team used PET-CT imaging to track where glucose was being taken up during cold exposure. Brown adipose tissue did increase its glucose uptake, but modestly. But the dominant shift occurred in skeletal muscle, where a process called GLUT4 translocation increased significantly. GLUT4 is a glucose transporter protein that sits inside muscle cells. When it moves to the cell surface, it acts like an open door, allowing glucose to flow from the bloodstream into the muscle without requiring as much insulin. In the Hanssen study, cold acclimation increased basal GLUT4 translocation, meaning muscle cells were pulling in more glucose even at rest. Because skeletal muscle accounts for roughly 40% of total body mass, even a small percentage increase in its glucose uptake capacity has a far larger metabolic impact than a large percentage increase in brown fat activity, which represents only a few hundred grams of tissue in most adults.
A 2021 review by Ivanova and Blondin in the Journal of Applied Physiology confirmed this hierarchy. Across the available literature, repeated cold exposure lowered fasting glucose and insulin levels in healthy individuals, and skeletal muscle was identified as the most significant contributor to glucose clearance during cold, owing to its sheer mass.
Denis Blondin, a physiologist at the Université de Sherbrooke who has studied cold-induced metabolism extensively, has been among the most direct voices on this point. “Some of the improvements in insulin sensitivity appear to be even better than what you’d see with exercise, which is kind of the surprising part,” he told NPR in 2023. That comparison comes from acute physiological data, not long-term head-to-head trials, but it points to something real: cold appears to trigger some of the same muscle-level glucose uptake pathways that exercise does. Which is why the next study from the Maastricht group matters so much.
The shivering question: what happens when you remove it
If skeletal muscle is driving the insulin sensitivity improvement through glucose uptake, an obvious question follows: does the muscle need to contract? Does the person need to shiver?
Schrauwen’s group tested exactly this. In 2021, Remie and colleagues published a follow-up in Nature Communications using a nearly identical ten-day cold acclimation protocol, but with one critical difference: the temperature was kept at 16–17°C (about 61–63°F), just warm enough to prevent shivering. Participants still felt cold. Their bodies still activated thermoregulatory responses. But they didn’t shiver.
After ten days at the warmer temperature: no improvement in insulin sensitivity. No metabolic benefit appeared — and no upregulated muscle contraction pathways either. When the muscles didn’t contract, the glucose transporter response didn’t appear.
This is the most important complicating finding in the entire cold-and-blood-sugar literature. It suggests that passive cold sensing alone, the kind of mild cold that makes you reach for a jumper but doesn’t make you shiver, may not be sufficient to produce the metabolic changes observed in the Hanssen study. The muscle has to do something.
A 2024 study by [Adam Sellers, a metabolic physiologist at Maastricht University, and colleagues, published in Nature Metabolism](https://www.nature.com/articles/s42255-024-01172-y), extended this line of investigation. Fifteen adults with overweight or obesity were exposed to cold conditions sufficient to induce roughly one hour of shivering per day, over ten consecutive days. Participants showed improvements in oral glucose tolerance, fasting glucose, triglycerides, and blood pressure. Critically, these were adults closer to the metabolic syndrome profile than the lean, healthy participants in many cold exposure studies. And the findings were consistent with the shivering hypothesis.
“The results are highly promising and may eventually suggest an alternative treatment or preventative measure for type 2 diabetes,” Sellers told EurekAlert. He also noted that cold exposure could offer a passive route to metabolic improvement for people who find traditional exercise difficult because of pain, mobility limitations, or other barriers – a point Blondin has raised as well.
From the laboratory to the ice bath: the translation gap
The studies above used room cooling: participants sat in mildly cold environments for hours at a time, wearing normal clothing, over ten-day periods. That is not what most people do when they step into a cold plunge.
Cold water immersion typically involves water at 2–10°C (36–50°F) for durations of two to eleven minutes. It is colder, shorter, and more intense than the laboratory protocols. Whether it produces the same metabolic effects is an open question, and the evidence is thinner.
One relevant data point comes from Gibas-Dorna and colleagues, who published a 2016 study in the Journal of Thermal Biology looking at the metabolic effects of six months of regular cold water swimming. Lean female participants showed improved insulin sensitivity. Without a control group, and with participants who were already lean, the findings are limited. But they are directionally consistent with the laboratory research and represent the closest available evidence from real-world cold water immersion.
What the research points toward is straightforward: the cold must be sufficient to provoke a meaningful physiological response, likely including some degree of shivering or significant muscle tension. A tepid cool-down probably won’t do it. A brief but genuinely cold immersion, the kind that produces visible shivering during or after exposure, is more consistent with what the evidence suggests matters. Research by Susanna Søberg at the University of Copenhagen supports ending on cold and allowing the body to reheat naturally, which extends the period of active thermogenesis, though her work focused on brown fat activation and overall metabolism rather than insulin sensitivity specifically.
None of this constitutes a clinical protocol.
What the evidence does not show
It would be easy, and irresponsible, to present these findings as a breakthrough diabetes treatment. They aren’t. Not yet.
Sample sizes are small: eight participants in Hanssen, fifteen in Sellers. These are early-stage investigations published in top-tier journals, not large-scale randomised controlled trials. Replication in larger, more diverse populations is needed before these findings can inform clinical guidelines. No long-term data exists either. The protocols lasted ten days. Whether cold exposure produces sustained insulin sensitivity improvements over months or years, or whether the benefit reverses when the exposure stops, remains unknown.
Translation from lab to life is also unresolved. Laboratory protocols used hours of mild cold. A five-minute ice bath is a fundamentally different stimulus. The metabolic pathways may overlap, but no study has directly compared the two approaches in a diabetic population.
And cold exposure, even if it proves clinically viable, would sit alongside medication, dietary management, and physical activity, not in place of them. That is not a disclaimer. It is an accurate reflection of where the science stands. Individual responses will vary as well. Brown fat volumes differ between people. Shivering thresholds differ. Cardiovascular responses to cold differ. For people with diabetes who may have autonomic neuropathy, peripheral neuropathy, or cardiovascular complications, cold exposure carries additional considerations that warrant discussion with their medical team.
Where this evidence sits
Maastricht’s cold-and-insulin-sensitivity research programme represents some of the most rigorous work in the broader cold therapy evidence base. Published in Nature Medicine, Nature Metabolism, and Nature Communications, it is mechanistically coherent: each successive study refines the understanding of how cold affects glucose metabolism and under what conditions. And it identifies a specific, testable boundary condition. Shivering appears to be required.
That last point is what separates this body of work from the vague claims that circulate through the wellness world. The researchers found something striking, then tested whether it held under different conditions, and honestly reported when it didn’t. That is how science earns trust.
For someone managing type 2 diabetes, pre-diabetes, or metabolic syndrome, this research doesn’t prescribe a treatment. It describes a mechanism. Cold exposure, when intense enough to produce muscular contraction, appears to drive glucose from the bloodstream into skeletal muscle through a pathway that partly bypasses insulin resistance. That is a real and specific finding, worth understanding clearly and worth discussing with a clinician. The cold has something real to say about blood sugar. The question now is whether clinical medicine is ready to listen.
