Intermittent cold exposure (ICE) has become increasingly popular, driven by claims of improved mood, immune function, and potential benefits for weight management. With obesity and type 2 diabetes reaching epidemic proportions, any strategy that can effectively reduce body weight or improve metabolic health is worth exploring. This article delves into the research surrounding ICE and its effects on adipose tissue, examining the potential for cold water and other cold exposure methods to contribute to weight loss.
Adipose Tissue and Metabolic Health
Dysfunctional adipose tissue plays a significant role in metabolic syndrome (MetS), a cluster of conditions including abdominal obesity, high blood sugar, hypertension, and dyslipidemia. MetS is a major contributor to heart disease, stroke, and cognitive impairments. Healthy adipose tissue is essential for maintaining metabolic health, prompting research into methods for enhancing its function.
While some drugs, like thiazolidinediones (TZDs), have shown promise in improving glucose homeostasis by acting on adipocytes, they come with undesirable side effects such as weight gain and cardiac complications. Lifestyle modifications, including diet and exercise, have emerged as logical approaches to promote weight loss and combat metabolic abnormalities. Recently, ICE has gained traction as a potential modulator of body weight and adipose tissue function.
Intermittent Cold Exposure (ICE): How It Works
Cold exposure challenges the body's ability to maintain a stable internal temperature, triggering a series of defensive responses. These include:
Sympathetic Nervous System Activation: The body's "fight or flight" system is activated, leading to the release of hormones like noradrenaline.
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Shivering: Rapid muscle contractions generate heat.
Non-Shivering Thermogenesis: Brown adipose tissue (BAT) is activated to metabolize substrates and produce heat.
BAT is a specialized tissue that burns energy at a high rate, making it a key player in maintaining core body temperature during cold exposure. The activation and potential expansion of BAT have been proposed as a way to combat obesity by increasing energy expenditure (EE). Furthermore, white adipose tissue (WAT), which typically stores energy, may undergo a transformation toward a BAT-like phenotype, a process known as "beiging" or "browning."
Research on ICE and Adipose Tissue
This article summarizes the current research on intermittent cold exposure as an intervention for obesity and metabolic syndrome, focusing on the effects of repeated ICE on adipose tissue.
Methodology of Studies
A review of available literature reveals varied methodologies in studies examining the effects of ICE on adipose tissue and body weight. These studies span from 1979 to 2023. The majority of studies focus on rodents, with a mix of rat and mouse models, while some research includes human subjects.
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There is considerable variability in ICE protocols, with durations ranging from less than 5 minutes to 8 hours and intervention periods lasting from 2 weeks to 6 months. Rodent studies primarily use cold rooms (air), while human studies employ air, water-cooled suits, cold showers, and cold water immersion. Cold showers and cold water immersion are more practical for human implementation, although most existing research involves rodents in cold rooms. ICE frequency is generally consistent, with most studies using 5 days per week or daily exposure.
Effects of ICE on Body Weight (BW)
The impact of ICE on body weight is inconsistent, with studies reporting increases, decreases, and no change. Human studies generally show no change in BW but may report modest reductions in waist circumference. Rodent studies account for much of the variability.
ICE duration appears to play a role. Studies comparing different durations of ICE found that shorter durations may lead to more substantial increases in BW. The intensity of ICE, as measured by temperature, may also be a factor, with more intense ICE temperatures resulting in decreased BW. The length of ICE interventions does not appear to be a significant explanatory factor.
Overall, an absence of effect of ICE on BW is expected when the balance between energy expenditure (EE) and energy intake (EI) is maintained. Many studies report an increase in EI as a result of ICE. However, some studies that controlled EI still reported an increase in BW.
Effects of ICE on Energy Expenditure (EE)
Studies generally indicate that ICE increases energy expenditure, and this increase is further amplified with increased ICE duration. However, ICE may induce increased EE during sleep periods but decreased EE during active periods.
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Effects of ICE on White Adipose Tissue (WAT)
ICE tends to increase subcutaneous WAT (sWAT) and has variable effects on visceral WAT (vWAT), with some studies reporting increases, decreases, and no change. Winter swimmers have shown increased fat mass but a decrease in vWAT.
In rodents, ICE has been shown to increase WAT multilocularity, suggesting a transition to a more metabolically active beige phenotype of WAT and an increased thermogenic capacity. This finding is consistent with other morphology-based reports of ICE-induced WAT beiging. While reports on changes in WAT mass are inconsistent, sWAT tends to increase in response to repeated ICE. Overall, studies support ICE as a protocol for inducing a beige adipocyte morphology, which is associated with increased mitochondria and thermogenesis, potentially improving the metabolic activity of WAT.
Effects of ICE on Brown Adipose Tissue (BAT)
ICE tends to increase BAT weight, although some studies report no change or a decrease. Regardless of the effect on weight, ICE consistently increases the thermogenic response of BAT to cold stress in both rodents and humans. Interestingly, BAT activation may be decreased at thermoneutrality in humans who participate in ICE compared to those who do not. Notably, ICE has been shown to induce measurable BAT activity in individuals who initially had low or non-detectable BAT activity.
Combining ICE with Exercise
Some studies have explored the combined effects of ICE and exercise. While ICE alone increases EE, BAT activation, and WAT beiging, there is no clear evidence that it can decrease fat mass (FM) and body weight (BW). In fact, some studies report increased BW and FM, which may indicate compensatory mechanisms due to increased EI.
The increase in BW and FM seems to be predominantly in sWAT rather than vWAT, which is generally associated with poorer metabolic outcomes. Furthermore, both sWAT and vWAT consistently adopt a beiging phenotype in response to ICE, suggesting that the transition from an energy-storing phenotype to a more metabolically active tissue could provide additional benefits.
ICE-induced weight loss may be possible when combined with caloric restriction.
Practical Applications of Cold Water for Weight Loss
How Cold Water Boosts Metabolism
Drinking cold water can lead to a surge of noradrenaline, similar to the effect of smoking or drinking coffee, which can boost metabolic rate. However, this effect may be blocked by beta-blocker drugs. The trigger appears to be osmolarity, the concentration of substances in a liquid, with plain water being more effective than sweetened beverages.
Temperature Matters
Cold water is more effective at boosting metabolic rate than warm or tepid water. Drinking cold water causes the body to expend energy to maintain its core temperature. However, the number of calories burned by drinking cold water is relatively small.
How Many Calories Are Burned During a Cold Plunge?
A ten-minute cold plunge burns only 10-20 additional calories. However, as the body becomes more efficient at maintaining core body temperature, metabolism will improve.
Activating Brown Fat
Cold exposure activates brown fat and recruits white fat to become brown fat. As brown fat grows, the body becomes more efficient at using energy to regulate body temperature, thus speeding up metabolism.
Stimulating Lymphatic Drainage
When the body gets cold, muscles tighten and constrict, encouraging the lymphatic system to release toxins and detoxify the body. Cold water immersion can help reduce the amount of lymph fluid buildup in cells and organs, improving body function.
Enhancing Alertness, Energy, and Discipline
Cold water immersion can increase noradrenaline and dopamine levels, which are associated with energy, focus, motivation, memory, alertness, and elevated mood levels. Regularly putting the body through the difficulty of cold plunging can improve confidence and resilience, which can extend to other areas of life, including fitness and diet.
Strengthening the Immune System
Cold water immersion causes the body to release cold shock proteins, which activate natural healing capabilities and increase white blood cell production. This can help prevent sickness, which can slow down or stop a weight loss journey.
Potential Risks of Drinking Cold Water
While generally safe, drinking cold water may have some drawbacks:
Difficulty in Digestion: Some believe cold water contracts the stomach, making digestion harder, and that the body has to work harder to maintain its internal temperature.
Nasal Congestion: Cold water can thicken nasal mucus, potentially worsening congestion during a cold or flu.
Headaches and Sore Throat: Cold water may trigger migraines in susceptible individuals and worsen pain related to esophageal spasms.
Imbalance in the Body: Traditional Chinese medicine suggests cold water with hot food creates imbalance.
Benefits of Drinking Cold Water
Prevents Overheating During Exercise: Drinking cold water during exercise can help keep the body from overheating.
Reduces Appetite: Consuming a large glass of water can help curb cravings and reduce food intake.
Boosts Metabolism: Water promotes fat burning, and cold water may require the body to burn extra calories during digestion to maintain its core temperature.
Warm Water vs. Cold Water
Warm water may support digestion, improve circulation, and help the body eliminate toxins faster. However, it may also reduce thirst, potentially leading to inadequate hydration.
The Ice Hack Diet
The ice hack diet involves consuming ice and other cold food and beverages to aid weight loss. Proponents suggest this may boost metabolism through cold-induced thermogenesis. However, there is a lack of scientific evidence investigating the ice hack diet and its impact on weight loss.