Thermogenic Foods Activate Brown Fat
- Thomas P Seager, PhD
- Nov 6, 2025
- 9 min read
Updated: Dec 14, 2025
These spices warm you from the inside
Summary
The discovery of brown fat in adult human bodies over twenty years ago started a radical reconceptualization of metabolism, adipology, endocrinology, and oncology that is still underway.
While pharmaceutical efforts to develop patentable drugs for activation of brown fat have failed, certain foods have profound metabolic effects by modifying brown fat function, including hot peppers, green tea, ginger, and cinnamon.
People seeking to build cold tolerance, including those with Raynaud's or thyroid disorders that disrupt thermoregulatory processes, might try eating thermogenic foods to help prepare themselves for a practice of cold plunge therapy.
Discovery Reveals Medical Misconception
Twenty years ago, medical doctors mistakenly believed there was no such thing as brown fat in an adult human body. They understood that human babies had brown fat, and they understood that rodents and other mammals had brown fat, but they thought that brown fat essentially disappeared from the human body during puberty.
They were wrong, and it was positron emission tomography (PET) for cancer imaging that proved it.
When doctors wants to image a tumor, they sometimes give the patient a radioactive form of glucose. Because tumor cells preferentially metabolize glucose, the radioactive tracer accumulates at the site of the tumor, which shows up as a dark blotch on the scan.
A PET machine uses a massive amount of electricity, and to keep the instrument functioning properly, the instrument rooms are kept cool. Sometimes, a patient wearing only a flimsy nightgown will get the chills.
Scientists in Switzerland were the first to notice that some cancer patients had symmetrical black depots showing up on their PET scans that couldn't possibly be tumors. They reasoned that the radioactive glucose tracer must also be accumulating in brown fat (Hany et al. 2002).
All over the world, scientists and medical doctors rushed to confirm these surprising findings (e.g., Saito et al. 2009). A "renaissance" in understanding of human metabolism was taking place in real time (Lee et al. 2013). Textbooks had to be rewritten and medical schools had to revise their teachings. A fundamental misconception in human adipology had been revealed, and it set off a chain reaction of new research in related fields like oncology (Seki et al. 2022) and endocrinology. Now, it's possible to do an entire doctoral dissertation in the same brown fat that doctors thought never even existed (Søberg et al. 2021).
Brown Fat Targeted for Obesity Treatment
While detectable brown fat is rare in adults who do not practice regular cold exposure, where it can be detected higher levels of brown fat are associated with leaner body composition, improved insulin sensitivity, and healthier, longer life. Generally speaking, the presence and activity of brown fat indicates metabolic health. Professor Deni Blondin considers brown fat a sentinel organ that provides the earliest indication of adverse metabolic injury.
Because activation of brown fat is associated with fat-burning, it has become a target for obesity drug development. In theory, a pill that could activate brown fat would increase basal metabolism, increase caloric consumption, alter energy balance and promote weight loss. In practice, this has never been achieved, partly because pharmaceutical companies failed to make a distinction between the rodent models in which drugs are typically tested and developed, and the physiology of human brown fat, which lacks a critical chemical receptor. As a result, millions of dollars of drug research and development money has been wasted in trying to put inside a pill what could better be accomplished by cold plunge therapy (Carpentier et al. 2023).
Brown fat activity is regulated via both nervous system and chemical (i.e. hormonal) signaling. For example, when thermal receptor in the skin sense cold temperatures, they signal the hypothalamus, which sends a signal to brown fat and other tissues to begin the process of thermogenesis. When I talked with Ohio State University Professor Kristy Townsend, she told me that she believes the communication between brown fat and the nervous system is likely bidirectional. That is, the brain modifies brown fat, and brown fat modifies the brain, even if the mechanisms are not yet understood.
However, it's not the only method by which brown fat communicates with other organs of the body. There is also chemical signaling, in which hormones and neurotransmitters like norepinephrine produced elsewhere in the body are released into blood circulation to signal activity within brown fat. Thus, brown fat plays an indispensable role in balancing the endocrine system. In The Cold Connection to Hashimoto's Thyroiditis I described how a regular practice of cold plunge therapy helped Courtney Hunt MD and other resolve thyroid disorders.
Brown fat and the thyroid work in concert to regulate metabolism. For example, brown fat converts the inactive form of thyroid hormone to the more active form, and in this way can produce more active thyroid hormone than the thyroid gland. When a body lacks sufficient cold exposure to maintain brown fat, thyroid disorders can result, which explains why Raynaud's is considered a clinical marker of thyroid dysfunction (Batthish et al. 2009).
In Calories and Cold Plunge, I described my views on the use of cold plunge therapy for weight loss. I'm not a proponent. My experience has been that cold plunge therapy can improve body composition by rebalancing sex hormones like testosterone, can reduce weight by resolving inflammation, can remodel fat from the dangerous visceral to the benign subcutaneous, and improve metabolic function. Nonetheless, I doubt that cold plunge therapy is an effective strategy for losing more than about 10 lbs. That is, the health benefits of cold plunge are legendary, but dramatic weight loss isn't likely one of them unless cold plunge is accompanied by other diet and lifestyle changes.
Foods that Activate Brown Fat
Despite the failure of the pharmaceutical company attempts to fit cold plunge in a pill, there are certain foods that will activate brown fat, stimulate thermogenesis, and increase caloric expenditure in the short term. You might find that eating small quantities of these foods right before your ice bath takes some of the sting out of the cold, and they might consequently be useful for people (like those with thyroid disorders, poor cold tolerance, or full-blown Raynaud's) trying to build their cold tolerance.
Hot Chili Peppers
In a recent interview, Chef Alex Belew explained that spicy foods like hot peppers contain capsaicin (cap-SAY-sin), which is the chemical that makes them feel “hot” in our mouth. It turns out that capsaicin and other chemicals in food can also activate brown fat, causing it to produce heat. In this way, “hot” foods are just spicy, they’re also thermogenic (Saito 2015). Capsaicin causes an increase in energy expenditure that can shrink white fat cells, reduces inflammation, and is already approved as a treatment for neuropathic pain (Silva et al. 2023). In other words, hot chili peppers mimic many of the same effects that ice baths do.
Ginger and green tea
Ginger and green tea are also thermogenic, albeit not because of capsaicin. Over a decade ago, researchers at Columbia University in New York City compared the effects of a powdered ginger tea with breakfast to zero-ginger controls. They found that drinking ginger tea with breakfast increased energy expenditure and curbed appetite among obese middle-age men (Mansour et al. 2012). Since then, researchers in Turkey investigated the effect of a ginger-green tea supplement on active men exercising in the cold. They found that “in cold conditions, combined supplementation significantly enhanced time to exhaustion, reduced respiratory exchange rate, and improved thermal sensation.” Ginger alone also improved thermal sensation and reduced muscle soreness, but only for the group that exercised in the cold (Demirli et al. 2025). Ginger in a warm environment had no benefit for exercise.
Cinnamon is a minor metabolic miracle
Cinnamon may be even more powerful for mitochondria than hot peppers, ginger, or green tea. In mice exposed to intermittent cold, administering cinnamon extract activated brown fat, metabolized white fat for thermogenesis, and improved mitochondrial function, compared to controls (Li et al. 2021). Specifically, cinnamon improved cold tolerance in the mice by increasing fat metabolism. Similar findings using pepper and cinnamon were found in rats (Pandit et al. 2018).
In humans, cinnamon is believed to have medicinal properties related to the action of insulin. That is, cinnamon improves insulin sensitivity, which ameliorates all the adverse health impacts of insulin resistance, including cancer, diabetes, dementia, and obesity (Błaszczyk et al. 2021).
Thermogenic Foods for Cold Plunge Therapy
In my article Getting Started in Cold Plunge Therapy, I described several ways that people might begin a practice of deliberate cold exposure without having to start in a 34F ice bath. However, I never talked about the potential role of thermogenic foods in preparing the body or as a complement to cold plunge therapy. For example, laboratory experiments suggest that cinnamon improves cold tolerance.
One of the questions I often get from my readers sounds like "I love ice bath, but how do I get my spouse to do it with me?"
Joe Rogan is the most important example.
Joe famously enjoys his Morozko Ice Bath at a freezing 33F. He even teased Stanford Professor Andrew Huberman for cold plunging at temperatures exceeding 40F and told Gary Brecka that the "Morozko sucks worse and that's why I like it."
The problem for Joe is that his wife won't tolerate the freezing cold temperatures that he will. So if they want to get cold together, and enjoy the love hormone rush I wrote about in Love in the Ice Bath they either have to reach a compromise on temperature or figure out something else. When Joe wrote to me in 2024 to ask if we could build a Joe Rogan model Morozko for his wife and mark it "HERS," I didn't yet know about thermogenic foods. In retrospect, I might have encourage them to try a green tea with ginger, cinnamon, and honey to see if that makes the freezing ice bath more tolerable for her.
What about you?
If you try this new thermogenic tea, or decide to combine some hot peppers with your ice bath, will you comment below to let me know what you experience?
References
Batthish M, Costigan C, Killeen OG. Raynaud's Phenomenon as a Presenting Feature of Hypothyroidism in an. The Journal of Rheumatology. 2009;36(1):203.
Błaszczyk N, Rosiak A, Kałużna-Czaplińska J. The potential role of cinnamon in human health. Forests. 2021 May 20;12(5):648.
Carpentier AC, Blondin DP, Haman F, Richard D. Brown adipose tissue—a translational perspective. Endocrine reviews. 2023 Apr 1;44(2):143-92.
Demirli A, Ulupınar S, Terzi M, Özbay S, Özkara AB, Gençoğlu C, Ouergui I, Ardigò LP. Synergistic Effects of Green Tea Extract and Ginger Supplementation on Endurance Performance and Thermal Perception in Normothermic and Cold Environments: A Randomized, Placebo-Controlled, Double-Blind Crossover Trial. Nutrients. 2025 Sep 13;17(18):2949.
Enerbäck S. Human brown adipose tissue. Cell metabolism. 2010 Apr 7;11(4):248-52.
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Lee P, Swarbrick MM, Ho KK. Brown adipose tissue in adult humans: a metabolic renaissance. Endocrine reviews. 2013 Jun 1;34(3):413-38.
Li X, Lu HY, Jiang XW, Yang Y, Xing B, Yao D, Wu Q, Xu ZH, Zhao QC. Cinnamomum cassia extract promotes thermogenesis during exposure to cold via activation of brown adipose tissue. Journal of Ethnopharmacology. 2021 Feb 10;266:113413.
Mansour MS, Ni YM, Roberts AL, Kelleman M, RoyChoudhury A, St-Onge MP. Ginger consumption enhances the thermic effect of food and promotes feelings of satiety without affecting metabolic and hormonal parameters in overweight men: a pilot study. Metabolism. 2012 Oct 1;61(10):1347-52.
Pandit C, Sai Latha S, Usha Rani T, Anilakumar KR. Pepper and cinnamon improve cold induced cognitive impairment via increasing non-shivering thermogenesis; a study. International Journal of Hyperthermia. 2018 Dec 31;35(1):518-27.
Saito M, Okamatsu-Ogura Y, Matsushita M, Watanabe K, Yoneshiro T, Nio-Kobayashi J, Iwanaga T, Miyagawa M, Kameya T, Nakada K, Kawai Y. High incidence of metabolically active brown adipose tissue in healthy adult humans: effects of cold exposure and adiposity. Diabetes. 2009 Jul 1;58(7):1526-31.
Saito M. Capsaicin and related food ingredients reducing body fat through the activation of TRP and brown fat thermogenesis. Advances in Food and Nutrition Research. 2015 Jan 1;76:1-28.
Seki T, Yang Y, Sun X, Lim S, Xie S, Guo Z, Xiong W, Kuroda M, Sakaue H, Hosaka K, Jing X. Brown-fat-mediated tumour suppression by cold-altered global metabolism. Nature. 2022 Aug 11;608(7922):421-8.
Silva JL, Santos EA, Alvarez-Leite JI. Are we ready to recommend capsaicin for disorders other than neuropathic pain?. Nutrients. 2023 Oct 21;15(20):4469.
Søberg S, Löfgren J, Philipsen FE, Jensen M, Hansen AE, Ahrens E, Nystrup KB, Nielsen RD, Sølling C, Wedell-Neergaard AS, Berntsen M. Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men. Cell Reports Medicine. 2021 Oct 19;2(10).
About the Author
Thomas P Seager, PhD is an Associate Professor in the School of Sustainable Engineering at Arizona State University. Seager co-founded the Morozko Forge ice bath company and is an expert in the use of ice baths for building metabolic and psychological resilience.
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