Wed, 08 Dec 2021

Brown adipose tissue, or BAT, has been found to have a major role in adult humans. In fact, it can account for about 10% of the total body weight and is more prevalent than other kinds of fat. This discovery will change how we think about obesity because BAT was previously thought not to be present in adults at all. The study's findings by exipure reviews also show that people with higher levels of brown fat are thinner and healthier while those with lower levels are heavier and unhealthy. Scientists believe this could lead to a new way to fight obesity by giving drugs that stimulate the production of brown fat cells or blocking hormones that inhibit its development. Researchers hope their findings

How to Calculate BAT

We investigated epidermal thickness, MRI contrast agent uptake, and blood flow to BAT deposits in 14 adult humans with varying degrees of body fat [10 males, 4 females; BMI 20-41•9 kg/m²]. We found a strong correlation between BAT volume and body fat percentage (adjusted R-square 0•73, P=0•006). We also detected large intersubject variability in BAT volume. In two subjects we found no evidence of brown adipose tissue.

We estimate the total BAT content to be around 40 g in this cohort, which corresponds to ∼2% of total body weight. The amount of active BAT is likely even lower due to the presence of vasoconstriction resulting from catecholamines produced by BAT itself prior to cold exposure. Our findings are consistent with earlier studies that have found that humans have very low levels of metabolically active BAT compared with other mammals. From the data presented here, it is clear that PET imaging combined with MRI is an excellent method for the identification of BAT in adults. However, supplementation with radiotracers like 18F-FDG (which has no known biological activity) may yet be required to detect metabolically active BAT in most adult humans.

A number of studies have shown that fat evolved to be stored during times when food was abundant and not needed suddenly or urgently - that would be a very poor survival strategy. For most of human history until quite recently (say, 5 generations ago), food was not always available on demand so being able to store some extra calories as fat meant you would have them when food was scarce.

Natural selection favors high levels of body fat on average because more people are likely to survive better if they can store the extra energy in the form of fat - remember that people like me (and presumably you) are descended from ancestors who survived long enough to reproduce. Theoretically, someone with low body fat might have an advantage in hot climates because they dissipate heat better. Evidence suggests that this is not the case, however.

It's also worth noting that high levels of body fat do not impair physical performance (in fact obesity is associated with longer life expectancy). Conversely, lack of muscle causes impaired physical performance and rapid fatigue which means you would be more likely to starve or get killed before breeding age anyway.

So what about people whose lifestyle involves constant exercise? Surely then it would be advantageous for them to have very low levels of body fat, to reduce drag when swimming for example? Well no, because the energy expended during exercise is tiny compared with expenditure while resting. To be an effective fat-storing organism you'd have to eat all the time just to maintain your weight - otherwise, you'd lose weight! That's impractical unless you can store excess food energy in some other way.

So nature has evolved a degree of fatness that is high enough not to impede survival but low enough not to cause health problems through lack of muscle or resistance to heat dissipation. For many people today, their body mass index (BMI) lies within this range though it may be too much for comfort Some athletes are good examples of this phenomenon. It used to be thought that obesity was associated with poorer athletic performance but that was before the athletes in question started to take anabolic steroids. These drugs suppress appetite and boost muscle mass so it's possible for an endurance athlete, for example, to have a BMI of 30+ while being very fit - compared to normal people who are overweight at least.

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