How much brown fat does the average person have?

November 30, 2025 •

4 min read

While newborns have a higher proportion, the amount of brown fat does the average person have as an adult is surprisingly low and highly variable. Advanced imaging shows that most adults retain small, yet metabolically active, deposits that play a key role in energy expenditure.

Quick Summary

The average adult has very small and variable deposits of brown fat, which decline from higher levels in infancy. This fat is metabolically active and burns calories for heat production.

Key Points

Variable Amount: The average adult has a small, yet metabolically significant, amount of brown fat, ranging from trace amounts to a few hundred grams.
Declines with Age: Brown fat is most abundant in newborns and decreases as people age.
Influenced by Weight: Leaner individuals typically have more active brown fat than those who are overweight.
Cold-Activated: Exposure to cold temperatures is the most direct way to activate brown fat's calorie-burning function.
Exercise and Diet: Both exercise (which increases irisin) and certain dietary choices can help promote brown fat activity.
Therapeutic Potential: Brown fat is a promising target for future treatments of obesity and metabolic conditions due to its thermogenic properties.

Understanding Brown Adipose Tissue

Brown fat, or brown adipose tissue (BAT), is a unique type of body fat with a critical function: to generate heat. Unlike white fat, which stores energy, brown fat is packed with iron-rich mitochondria that burn calories to produce warmth, a process known as thermogenesis. This ability is vital for newborns who cannot shiver to regulate body temperature. For adults, the discovery of functional brown fat was a significant finding, sparking new research into its role in weight management and metabolic health.

The Variability in Brown Fat Amounts

Determining exactly how much brown fat the average person has is complicated and influenced by a variety of factors. The amount varies from less than a gram to several hundred grams, constituting less than 0.5% of total body mass in most adults.

Factors influencing the amount and activity of brown fat include:

Age: Brown fat levels are highest in newborns and tend to decrease with age.
Body Composition: Leaner individuals, such as athletes, often possess more brown fat than overweight or obese individuals.
Environmental Temperature: Regular exposure to cooler temperatures can activate brown fat and increase its volume.
Genetics: Some people are simply predisposed to having more active brown fat than others.
Hormonal Activity: Hormones, including thyroid hormones and adrenaline, play a role in regulating brown fat activity.

Recent research suggests that previous estimates of brown fat mass might have been an underestimate. One study reported a mean brown fat mass of around 300g in normal-weight individuals, which is substantially higher than the earlier, more conservative figures.

Brown vs. White Fat: A Comparison

To understand brown fat's significance, it's helpful to compare it with the more common white fat. The two types of adipose tissue have distinctly different structures and functions.


Feature	Brown Adipose Tissue (BAT)	White Adipose Tissue (WAT)
Primary Function	Burns calories to generate heat (thermogenesis)	Stores energy in large lipid droplets
Mitochondria	Packed with numerous, iron-rich mitochondria	Contains very few mitochondria
Appearance	Brown due to high iron content in mitochondria	White or yellowish
Location (Adults)	Small deposits around neck, collarbone, spine	Throughout the body, particularly hips, thighs, and belly
Calorie Consumption	High metabolic activity; helps burn calories	Low metabolic activity; stores calories

How to Activate and Possibly Increase Brown Fat

Activating existing brown fat and potentially converting some white fat into a brown-like form (beige fat) has become a therapeutic target for weight management. While more research is needed, here are some strategies that show promise:

Cold Exposure: The most well-established method is exposure to cooler temperatures. This doesn't have to be extreme. Spending time in a cool room (around 66°F or 19°C), taking a cold shower, or using ice baths can trigger BAT activation.
Exercise: Physical activity stimulates the production of the hormone irisin, which has been shown to help convert white fat cells into more active beige fat cells. High-intensity interval training (HIIT) is particularly effective at raising irisin levels.
Diet: Some research points to certain foods and supplements that may have an effect. For example, compounds like capsaicin found in chili peppers have been linked to brown fat activity. A diet rich in whole foods and iron can also support healthy brown fat cells.
Maintain a Healthy Body Weight: Studies indicate that obese individuals have less active brown fat compared to lean individuals. Maintaining a healthy body weight can help ensure that existing brown fat remains functional.

The Therapeutic Potential of Brown Fat

The ability of brown fat to burn calories and improve metabolic function makes it a compelling area of study. The potential for targeting BAT to combat obesity and related metabolic diseases like type 2 diabetes has attracted significant interest from researchers. As scientists continue to uncover more about how brown fat is recruited and activated, new pharmacological and therapeutic strategies may emerge.

Conclusion

In conclusion, the average adult possesses only a small, variable amount of brown fat, far less than what is found in newborns. While modest, this tissue is metabolically significant due to its ability to generate heat and burn calories. Factors like age, body composition, temperature, and lifestyle choices all play a role in determining an individual's brown fat stores and activity. Although research is ongoing, simple strategies like controlled cold exposure and regular exercise can help activate this 'good' fat. The continued exploration of brown fat's potential offers a promising avenue for future therapies to address obesity and metabolic disorders. For more information on the latest research, the National Institutes of Health (NIH) is a great resource.(https://www.nih.gov/news-events/nih-research-matters/how-brown-fat-improves-metabolism)

Frequently Asked Questions

Brown fat is metabolically active and burns calories to produce heat (thermogenesis), whereas white fat primarily functions to store energy.

Newborns have higher levels of brown fat to help them regulate body temperature, as they cannot shiver effectively. Most of this brown fat dissipates with age.

You can activate and potentially increase your brown fat's activity through controlled cold exposure, regular exercise, and maintaining a healthy diet.

In adults, brown fat is found in small deposits around the neck, collarbone (supraclavicular region), spine, and near the kidneys and adrenal glands.

Studies suggest that brown fat can be activated by exposure to mildly cool temperatures, such as a room around 66°F (19°C), without inducing shivering.

Yes, brown fat burns calories to generate heat, which increases energy expenditure and could be a factor in weight management. Research is exploring its potential for obesity treatment.

Yes, a process called 'browning' or 'beiging' can convert white fat into beige fat, which has similar calorie-burning properties to brown fat. Exercise and cold exposure can induce this process.