What is the Difference Between Brown fat and White fat?

The word fat has all sorts of negative connotations; it is difficult to imagine a scenario where being described as ‘fat’ would be considered a compliment! Most of us strive to keep our body fat to a minimum, and that is, in general, a good thing. However, it is important to note that not all fat is bad; indeed, it can play a very important role in keeping the body healthy.

Brown fat, or brown adipose tissue (BAT), is commonly known as ‘good fat’. It is comprised of adipocytes (fat cells) containing small lipid droplets. BAT has a very rich blood supply, and its cells contain multiple iron-containing mitochondria (organelles responsible for energy production), which gives it its brownish hue. BAT comes from muscle tissue, and is responsible for converting chemical energy (food) into thermal energy (heat). It is typically located around the neck and upper back. Higher levels are found in infants and hibernating animals, with levels falling as we age. Those who do maintain high levels of BAT are generally younger, more slender and more active. This is due, in part, to exercise generating increased BAT; the high numbers of mitochondria making it very metabolically active;

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White fat, or white adipose tissue (WAT), is comprised of cells with large lipid droplets,very few mitochondria and minimal blood vessels, resulting in a lighter, more yellow colour. It is the most predominant form of fat in the body, originating from connective tissue. Whilst an excess of WAT is not good, moderate levels do help to reserve energy and protect the internal organs. WAT produces several proteins and hormones, most notably leptin, which is known to modulate appetite and stress levels, amongst other things. It also produces several pro-inflammatory factors, which explains why obesity is often associated with other immune-related disorders. Excessive WAT is also associated with the development of heart disease, type 2 diabetes, cancer, and inflammatory disease. Additional white fat is generated by consuming more calories than your body is able to burn, either naturally or via exercise.

The ideal scenario is to increase the levels of BAT and reduce WAT, which will improve an individual’s metabolism and weight management, as well as decreasing the likelihood of chronic complications associated with high WAT levels. This can be done by the consumption of a balanced diet that is rich in iron and polyunsaturated fatty acids (eg Omega 3 and 6), and by being physically active. In fact, several studies have suggested that WAT is actually plastic, and can turn into BAT under certain physiological conditions such as exercise, in a phenomenon termed ‘adipose browning’.

Sources:

• Lee, Y H, et al. “Adipose Tissue Plasticity from WAT to BAT and in between.” Biochimica Et Biophysica Acta, vol. 1842, no. 3, Mar. 2014, pp. 358–369., doi: 10.1016/j.bbadis.2013.05.011.
• Sepa-Kishi, D M, and Ceddia, R B. “Exercise-Mediated Effects on White and Brown Adipose Tissue Plasticity and Metabolism.” Exercise and Sport Sciences Reviews, vol. 44, no. 1, Jan. 2016, pp. 37–44., doi:10.1249/JES.0000000000000068.
• Peeke, P. “Not All Body Fat Is the Same. Learn the Difference for Better Health.” Women’s Health, 25 Apr. 2014, www.womenshealthmag.com/health/a19896462/fat-facts/.