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Guillermou's avatar
Guillermou
Nov 27, 2025

Swimming in cold water increases brown fat, which is essential for eliminating white fat. Studies have shown that brown fat is a protective system that eliminates excess nutrients from our diet, preventing them from being deposited as white fat, which leads to obesity. Brown fat is the opposite of white fat. It is found in the buttocks and abdomen, and it is crucial to eliminate any excess white fat.

White fat stores energy in the body, while brown fat does the opposite: it uses it. When exposed to cold, brown fat is activated by norepinephrine, which increases by up to 250% in a matter of minutes.

Once activated, brown fat uses sugar and fat from the bloodstream as fuel to raise body temperature. Therefore, its purpose is to retain heat and prevent death from hypothermia. It's truly ingenious that nature has given us this little radiator in our bodies. And this brown fat tissue will also keep you healthy because it uses stored calories in the body and increases your insulin sensitivity.

In daily life, there are several ways to help stimulate brown fat activity: physical exercise and being mindful of the thermal environment as a risk factor. High temperatures inhibit brown fat activity, so increasing outdoor activity and swimming in cold water are recommended.

People with higher levels of brown fat have a more active metabolism and greater insulin sensitivity. Younger and thinner people have more brown fat. Age leads to weight gain (white fat), while brown fat decreases, as does a more sedentary lifestyle. Cold weather and exercise increase brown fat. There is also another type of fat similar to brown fat, called "beige" fat, which increases with melatonin.

Swimming in cold water with a lower training volume has an additive effect on stimulating the expression of genes involved in white adipose tissue (WAT) darkening and brown adipose tissue (BAT) thermogenesis, compared to cold exposure or swimming alone. Furthermore, cold water swimming increases the number of brown fat cells in both brown adipose tissue and WAT deposits. Swimming in cold water with a lower training volume activates brown adipose tissue (BAT). The findings demonstrate that six weeks of cold water swimming training promotes additive effects on the expression of genes and proteins involved in the adipose tissue darkening process. Cold water swimming reshapes the gut microbiome to improve high-fat diet-induced obesity.

Dr. Bruce Spiegelman identified a “master switch” (PRDM16) that promotes brown fat production. Harvard's Joslin Institute found another factor that triggers brown fat: a bone morphogenetic protein called BMP-7, which also promotes bone growth. A fat-burning hormone called irisin, released during exercise, helps your body lose fat, improves heart function, reduces the risk of atherosclerosis, increases mitochondrial biogenesis, and induces telomere elongation in cells, thus improving your health and longevity.

Brown adipose tissue has a large number of mitochondria and a highly vascularized endoplasmic reticulum, and is involved in thermogenesis. It has been shown to play a significant role in lipid and carbohydrate metabolism, including triglyceride elimination. Furthermore, it secretes vascular endothelial growth factor, brain-derived neurotrophic factor, and nerve growth factor. Brown adipose tissue is an endocrine organ, just like white adipose tissue; it secretes various cytokines, hormones, and other factors.

Evidence, primarily from small interventional studies, suggests that cold water therapy positively impacts cardiometabolic risk factors, stimulates brown adipose tissue, and promotes energy expenditure, potentially reducing the risk of cardiometabolic disease. It also triggers the release of stress hormones, catecholamines, and endorphins, improving alertness and mood, which may alleviate mental health issues. Cold water therapy also reduces inflammation, strengthens the immune system, promotes sleep, and enhances recovery after exercise. The optimal duration and temperature required for maximum benefits are uncertain, but current evidence suggests that short-term exposure to lower temperatures may be more beneficial. Overall, cold water therapy presents a potential lifestyle strategy for improving physical and mental well-being, promoting healthy aging, and extending healthy lifespan, but definitive interventional evidence is warranted.

https://onlinelibrary.wiley.com/doi/full/10.1111/sms.12904 (2018)

https://pdfs.semanticscholar.org/b9e6/69e53f67b985793974ad0ef19588f54393b6.pdf (2018)

http://jeb.biologists.org/content/221/Suppl_1/jeb169425.article-info (2018)

https://academic.oup.com/endo/article-abstract/159/7/2520/4994581 (2018)

https://www.sciencedirect.com/science/article/abs/pii/S109649592300009X (2023)

https://outdoorswimmer.com/featured/what-happens-to-your-body-when-you-go-cold-water-swimming/ (2023).--

https://pubmed.ncbi.nlm.nih.gov/39093510/ (2024).—

https://www.mdpi.com/1422-0067/25/7/4055 (2024).--

https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2025.1589902/full (2025).--

https://link.springer.com/article/10.1007/s11357-024-01295-w (2025).--

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Guillermou's avatar
Guillermou
Nov 27, 2025

Alterations in the gut microbiota affect the host organism's energy balance; that is, they affect both the production of energy from the diet and the host genes that regulate energy expenditure and storage. Research summarizes the findings of recent years, emphasizing the effect of the gut microbiota on the development of obesity. It investigates the factors (diet, dietary components, lifestyle, and environment) that can affect the composition of the gut microbiota. Potential strategies for the prevention and/or treatment of obesity include restoring or modifying the microbiota composition through the consumption of prebiotics and probiotics, fermented foods, fruits, and vegetables, while avoiding ultra-processed foods loaded with trans fats and added sugars. Obesity can alter the gut microbiota both structurally and functionally, and the gut microbiota can also modulate nutritional status. The abundant and diverse quantity of certain bacteria can facilitate energy storage and metabolic pathways that lead to obesity. Furthermore, the gut-brain axis could be another possible pathway linking the gut microbiota to metabolism, and this bidirectional system can influence both host metabolites and appetite.

Among the Hadza hunter-gatherer tribe of Tanzania, the prevalence of obesity is very low, which researchers explain in terms of their diverse microbiome and diet. During the African rainy season, they maintain a predominantly plant-based diet dominated by roots, baobab, and wild honey. On the other hand, the Inuit of the Canadian Arctic have had a traditional diet for thousands of years, low in carbohydrates and high in fats and animal proteins, with characteristics similar to Western-type diets. This is reflected in their nutritional status, with 52.4% of men and 58% of women being overweight or obese.

The composition of the gut microbiome is clearly different in overweight individuals and athletes of all age groups: in the former, a decrease in Bacteroidetes taxa and an increase in Firmicutes taxa are observed, while in athletes, the opposite relationship is observed.

The HPA axis regulates bodily processes, including digestion, and releases corticotropin-releasing factor, which affects inflammation, permeability, and intestinal motility. The central nervous system (CNS) and the enteric nervous system (ENS) are associated with the functioning of the gastrointestinal tract.

Dietary interventions with probiotics, prebiotics, or synbiotics can be effective in reversing the alterations observed in the gut microbiota during obesity or unbalanced diets. Prebiotics are associated with the secretion of satiety hormones. Conversely, the use of food additives, such as emulsifiers, is linked to the obesity crisis, inflammation, and metabolic syndrome. The role of lipopolysaccharide (LPS) in disease development is clear. High-fat diets reduce the populations of Bifidobacterium spp., Lactobacillus spp., and Prevotella spp., and play a role in the overactivation of the endocannabinoid system, negatively altering the gut microbial composition. Furthermore, high-fat diets increase the overgrowth of Gram-negative pathogens, promoting the diffusion of bacterial fragments such as lipopolysaccharides (LPS) across the intestinal barrier. The endotoxin LPS can activate the nuclear factor kappa B (NF-κB) pathway, leading to increased intestinal permeability and thus facilitating weight gain. LPS translocation caused by a high-fat diet may be associated with low-grade chronic inflammation induced by obesity.

https://www.mdpi.com/2076-3417/13/1/610 (2022).--

https://www.mdpi.com/2076-2607/9/1/18 (2020).--

https://www.mdpi.com/2072-6643/16/5/660 (2024).--

https://www.mdpi.com/2076-2607/12/7/1341 (2024).--

https://www.mdpi.com/2076-2607/12/5/1020 (2024).--

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