Updated: Jul 21
" Too many people are confident that they know what fat is: an undesired body appendage that they strive to reduce over their entire lives. For those who struggle to lose weight, fat is often a source of misery, not marvel"; writes Dr Aaron Cypress of diabetes, endocrinology and obesity branch of NIH.
Let us take a deeper dive into what he means.
In a " lean" adult the fat tissue is 30-40% of total body mass in women and 15-20% in men. While there is no easily available way of precisely measuring total body fat( other than CT scan and MRI), waist circumference, BMI, bioimpedence scales can give a fair estimate.
Not only is the amount of fat in our body important, the location of fat is equally important. Fat accumulation around organs are thought to be more harmful than fat stored under our skin. That is why BMI measurement alone is sometimes deceptive.
The popular belief that people are born with all the fat cells they ever will have has now been proven wrong. Turns out all fat cells in the body are replaced every 15 years or so.
Fat tissue is predominantly of two types: brown and white(and some in-between: beige, pink, you name it!). Whether white fat (the undesirable variety) can metamorphose into the brown (desirable variety), remains a topic of speculation.
The white fat tissue helps us store energy and frees us from constantly seeking food, so we can direct our time at building civilization. It creates a layer of insulation in our body, resisting cold/injury etc.
White fat releases hormones like leptin which affects appetite and adiponectin which promotes a favorable metabolic/cholesterol profile and is anti inflammatory.
Interestingly enough though, white fat tissue can also increase risk of inflammation, in certain situations.
You may want to know how fat cells increase inflammation.
The answer is, when there is overgrowth of fat cells, that leads to oxygen deprivation in those cells ( as seen in obesity). It releases a pro inflammatory hormone. This is thought to be the reason for increased risk of heart attack, cancer and susceptibility to infections, like coronavirus, in people with increased BMI.
White fat tissue is important for proper function of the reproduction system. Too little fat, as seen in anorexia nervosa, can cause failure of menstruation. Too much can cause early puberty. Fat is needed for breast feeding.
The brown fat tissue helps our body generate heat. It releases hormones that improve our metabolism by increased consumption of glucose and fat by the muscles of our body.
Brown fat is, unfortunately, only 0.2-3% of the total body fat.
Activation of brown fat tissue has been found to be helpful in mice and have been hypothesized to be beneficial in humans, although there is need for more research.
Amount of brown adipose tissue decreases with age, and with increased BMI, increased ambient temperature.
The role of specific macronutrient (ie fat/carbs/protein) in weight gain remains a topic of hot debate and I will try to address this in future blogs.
In conclusion, in right amounts, fat is a friend. The ideal amount of fat varies from person to person and depends on race/sex, age etc. While a lot of research is still needed, keeping an eye on BMI (remembering ideal BMI may be different for different races), adopting an active lifestyle and controlling portion size has very little downside.