Brown Fat And Weight Loss: The Scientific Truth

Research focussed on treating obesity is growing rapidly. Day after day scientists invest a lot of their resources in solving this public health concern because obesity does not stop at weight gain.

It leads to prevalence of a number of other diseases like metabolic syndrome and diabetes. So obesity is beyond just body image.

So here is one of the different concepts that these guys are actively researching upon – fat that can prevent you from gaining weight. Sounds pretty ridiculous, since we are all trying to lose fat in the first place. And no this is the not the story about the good fats and bad fats. This is about brown fat.

What is brown and white fat?

Earlier adipose or fat tissue was thought to be a passive depot that stores fat. But further research showed that it is an active organ that secretes chemicals (adipokines) which impact other organs.

Previously you must have heard that there are two types of fat:

  • Visceral fat- the harmful one that surrounds the organs
  • Subcutaneous fat- the not so harmful one that lies below our skin

Well now here is another classification: Brown fat and White fat. They are not differentiated on the basis of location. White fat consists of single fat droplet and lesser mitochondria in a cell. Its function is store fat.

Brown fat consists of multiple fat droplets and many mitochondria enclosed in a cell that gives it the brown color. Its function is to burn fats.

The brown adipose tissue (BAT) is different from white adipose tissue (WAT) in terms of origin. BAT cells are similar to muscle cells and express a common gene called Myf5. As the BAT expands, it leads to generation of ‘brite’ (brown in white) or ‘beige’ adipocytes.

These are similar to brown adipocytes in structure and function but differ in terms of origin and genetic composition.

Earlier BAT was thought to be present in infants and newborn but further imaging techniques showed that adults also have BAT. It is present in the neck, shoulder and upper chest regions.

However the amount of BAT decreases with age and becomes indistinguishable from WAT. This would perhaps explain why we gain weight with age.

What are the functions of brown fat?

Brown fat has two functions:

  • Thermoregulatory thermogenesis: Producing body heat in response to cold environment.
  • Metaboloregulated thermogenesis: Burning off excess calories as body heat

Brown fat has high number of mitochondria. These are cellular organelles which facilitate respiration. However in brown fat cells this respiration leads to production of heat.

Babies have more brown fat since they can’t generate heat by shivering. The fact that it can expend excess calories, brown fat is implied to be useful in treating obesity and diabetes.

Also BAT activity is less in obese individuals compared to lean individuals and this could be a consequence or result of insulin resistance. This is why BAT is being thought of as a therapeutic target for diabetes and obesity.

What are the different biological molecules that aid in activity and development of brown fat?

The purpose behind introducing you to these terms is to make you understand that these are the possible therapeutic targets that are manipulated in order to activate BAT. Research is being organized to develop compounds or synthetically derive these proteins in order to develop brown fat but we will not venture into those details.

UCP1

It is a protein found in mitochondria of brown adipose tissue. It facilitates production of oxidation energy as heat and helps in maintaining body temperature.

BMP7

Animal studies report that bone morphogenetic protein 7 leads to increase in brown fat mass, increased energy expenditure and reduced weight  gain.

PRDM16

This is the most important protein when it comes to BAT related thermogenesis. BAT cells have the same origin as muscle cells. PRDM16 acts as a switch that regulates differentiation of cells into either brown adipocytes or muscle cells.  It also supports browning of white adipose tissue or development of beige adipocytes.

PGC-1alpha

Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is a protein that plays an important role in energy regulation and insulin sensitivity.   It is induced by cold exposure and mediates a number of processes like lipid, carbohydrate metabolism and cellular respiration.

FGF family

Fibroblast growth factors are a family of growth factors that are involved in multiple biological actions. FGF21 is found to ameliorate diet induced obesity in mice by activating BAT.

Brown fat as a therapy for obesity

The fact that this body fat raises metabolism and burns calories, researchers are finding ways to activate the existing BAT proportions in humans or stimulating formation of brite adipocytes.

One of the famous studies that led to the idea of BAT as a possible target for obesity therapy was conducted by Rothwell and Stock. In their experiment , they showed that a high calorie diet led to activation of BAT in mice and caused diet-induced thermogenesis thus preventing weight gain.

In humans, as little as 50g of BAT can consume 20% of daily calories upon maximum stimulation.  That translates to around 200-500kcal a day.

The colder it gets the better your brown fat functions

brown fat image 1The main function of BAT is to protect us from cold. The effects of chronic cold stimulation were studied in healthy individuals with low and undetectable BAT activity.

Repeated cold exposure at 17 degree Celsius for 2 hours every day for 6 weeks led to significant increase in BAT activity and decrease in fat.

Another study  investigating the role of BAT in glucose metabolism recruited men who were similar in age, BMI and adiposity. However a few had positive BAT activity while the rest were lacking. Prolonged cold exposure (5-8hr) caused an increase in resting energy expenditure, glucose metabolism and insulin sensitivity in those who had positive BAT activity.

However the presence of brown adipose tissue is less in obese individual and despite of cold exposure they show limited BAT activity than lean individuals.  Also daily cold exposure is a difficult idea to apply to regular life.

What does this mean?
The prime function of brown fat is to regulate body temperature. Therefore cold environments can stimulate development of brown fat. Even research work conducted shows that body scans taken in winter show active brown fat tissue.

The link between famous ‘Exercise’ hormone and brown fat

I don’t need to tell you much about the benefits of exercise irrespective of one’s body weight concerns.  Exercise strengthens BAT activity.  Researchers suggest that exercise increases the levels of a hormone called irisin.

Irisin activates BAT and is thought to hold therapeutic potential against diabetes and obesity.    But some theories suggest that irisin is not as effective as other biological molecules in activating BAT.

What does this mean?
Irisin is a hormone whose levels are heightened in response to exercise and it is known to aid in brown fat development. Active research is being conducted to evaluate how effective it is in raising BAT activity.

Sleep or rather sleep hormone activates brown fat

brown fat image 2The hormone that regulates are sleep-wake cycle, melatonin is said to help in weight loss. BAT’s activity of disposing of excess energy as heat is regulated by melatonin.   Research proves that chronic oral supplementation of melatonin causes WAT to follow brown fat’s function.

Melatonin supplements are available but one good way to boost the natural levels is to sleep well with minimum light exposure at night and good daylight exposure in the morning.

What does this mean?
Melatonin forces white fat to adopt brown fat’s attribute of burning calories and a good way to maintain healthy melatonin levels is to sleep well.

Pharmaceutical agents that boost brown fat activity

A number of drugs and hormones are being synthesized with the hope that they would target the various biological agents I have mentioned previously in relation to brown fat tissue development. You can skip this one if you are not a geek.

Beta3-adrenergic receptor agonist

Beta3-adrenergic receptors facilitate break down of fats and burning of fats or glucose to form energy. Agents that activate this protein are found to increase metabolism and reduce weight gain by increasing concentration of UCP1 by 2-3 folds.

A similar study conducted in lean men showed improved insulin sensitivity and fat oxidation  and other study in obese men reported short term increase in metabolism.

Unfortunately these studies didn’t take into account the existing levels of BAT in the volunteers.  Yet another study proved that Beta3-adrenergic receptor agonists increase metabolism by stimulating BAT activity.

However, long term administration of such drugs can reduce BAT activity due to downregulation of the receptors.

THR agonists

BAT activity is increased in those suffering from hyperthyroidism and therefore it is thought that thyroid hormones could help in BAT induced thermogenesis.

And indeed animal studies do show that activation of Thyroid Hormone receptors (THR) can increase metabolism and reduce fat accumulation.   However the level of thyroid hormones required raising metabolism can cause serious side effects.

BAIBA

Beta-Aminoisobutyric acid (BAIBA) is a substance secreted by muscle cells. Administration of this substance stimulates browning of white fat and stimulates energy expenditure.

What does this mean?
A number of synthetic drugs are being designed to act on various biological targets that aid in brown fat development. Their effectiveness and safety still needs to be evaluated.

Weight loss foods that aid brown fat to burn calories

Some common food items are known to perpetuate weight loss by activating BAT and related mechanisms.

Peppers

brown fat image 3The cold stimulus that activates the brown adipose tissue is received by transient receptor potential channels (TRP). These proteins can also be activated by a number of food ingredients.

Currently such compounds raise the daily energy expenditure by 2-5% but research suggests that we can expect a 10-15% increase in future.

Capsinoids, active ingredients of pepper, are found to activate TRP and also possess anti-obesity potential.  Daily ingestion of capsinoids for 6 weeks activates BAT just like activation by cold exposure and decreases body fat.

A short study  was conducted wherein 18 healthy men where the effect of cold exposure and capsinoid ingestion on BAT activation. Imaging reported that cold exposure activated energy expenditure in individuals with active BAT than those lacking in BAT. Oral ingestion of capsinoids however led to energy expenditure in both groups.

Ketogenic diet

Ketogenic diet is extremely low in carbs and high on fat and is a very popular weight loss diet. Recapturing the previous elements, FGF 21 is identified as a novel metabolic regulator that can serve to be therapeutic in treatment of diabetes and obesity.  It enables glucose utilisation in fat cells.

Animal studies show that ketogenic diets increase the levels of FGF21 which in turn increases energy expenditure and fat metabolism.    We could suggest ketogenic diets for weight loss but would it actually help in activating BAT activity remains a question.

Apple

Ursolic acid is a compound that is part of the waxy coating found on apples and other fruits and herbs.  A study published in June 2012 demonstrated that ursolic acid when fed to animals on a high fat diet prevented obesity by improving glucose metabolism and increasing the proportion of skeletal muscle and brown fat.

Thats how the suggestion to eat apple with peels to increase brown fat came up. But whether there is enough ursolic acid in apple peels to increase brown fat in humans is a question. Anyways apples have a plenty of other health benefits for which you could be convinced to eat it.

Resveratrol

Resveratrol is found in skin of grapes and berries. It activates the genes and proteins that improve mitochondrial function and as we know BAT is rich in mitochondria. The body fat lowering effect of resveratrol is mediated by increasing energy expenditure by BAT and browning of WAT.

Spices

Garlic is proven to exert anti-obesity effect by increasing BAT activity.  This study demonstrated that garlic supplementation lowered the genes that promote deposition of fat in WAT and increased the level of proteins that increase BAT’s ability to burn fat.

Brown fat decreases with age. A study conducted on animals showed that short term supplementation with curcumin, active component of turmeric, increases mitochondrial function in BAT tissue in aged mice.

What does this mean?
Natural foods like pepper, garlic, turmeric, apples raise or even ketogenic diets raise metabolism and perpetuate weight loss by activating brown fat.

Herbal solution for Brown fat activation

There are a number of weight loss herbs and many of them possess fat burning activities, but we stumbled upon two that target BAT and WAT, especially the first one.

Ephedra & Epehedrine

Norepinephrine is a brain related chemical released in response to stress. BAT is highly innervated by sympathetic  nerves and therefore the development of brown adipose tissue is controlled by norepinephrine.

Norepinephrine is a central nervous stimulant that has anti-obesity potential.

Ephedra is a medicine extracted from the plant Ephedra sinica. The most common alkaloids present in this medicine are ephedrine and pseudoephedrine. Their structure is similar to that of norepinephrine.

Nicotine and ephedrine are found to increase BAT activity.  A meta analysis showed that ephedrine and ephedra promote modest short-term weight loss but with a number of side effects which is why dietary supplements containing ephedra have been banned by FDA.

Bofutsushosan

Bofutsushosan is a Chinese herbal preparation that is used as an anti-obesity drug.  Animal study proves that this medicine prevents weight gain and diet induced obesity by increasing the expression of UCP1 in WAT.

What does this mean?
Herbal medications like ephedra and bofutsushosan are proven to raise BAT activity and convert WAT to BAT respectively. Ephedra in dietary supplements has been banned due to its serious side effects.

Surgical interventions targeting brown fat

If you are thinking of surgery as a means to transplant brown fat, yep researchers are already thinking about it.

Bariatric surgery

In bariatric surgery weight loss is achieved by reducing size of the stomach. A study shows that weight loss achieved by bariatric surgery activates BAT.

Prior to surgery only 2 out of 10 patients all of who were obese, showed active BAT. But one year post surgery the number increased to 5. This is an interesting finding that needs more research.

Autotransplantation

Now this one of the crazy but scientifically backed ideas that researchers have come up with. Since a lot is being discovered about the biology of BAT, they are envisioning creating active BAT in labs.

The idea is to obtain primary cells from an individual by liposuction or muscle biopsy, treat and grow it to form active brown fat tissue and then transplant it back to the donor.  Now the challenge is whether this will actually lead to weight loss or no.

What does this mean?
The activity of BAT is raised after weight loss post bariatric surgery. Transplantation and development of brown fat is still a vague idea that researchers need to work upon.

Highlights on how brown fat can help in weight loss

Research has put forward a number of ways to increase the activity of brown fat tissue:

  • Cold temperatures or cold baths can stimulate your brown fat to burn calories in order to maintain body temperature.
  • Exercise increases the level of irisin that activates brown fat.
  • Sleep hormone melatonin is beneficial for brown fat development and activity.
  • Active compounds of pepper, turmeric and garlic raise brown fat activity.
  • Ketogenic diet also stimulates brown fat function.
  • Ephedra and Bofutsushosan are herbal solution for activating brown fat.

Conclusion

One thing is clear that Brown fat is good fat and it works beyond just regulating our body temperature.  And blessed are the ones who have abundant active BAT that keeps them lean always.

Although it is proven that brown fat can used as a therapeutic target for obesity there are quite some points that can prevent us from making use of it in daily life.

Exposure to cold atmosphere, eating herbs or foods with the hope that it will activate brown fat in our bodies, sleeping well to modulate melatonin levels seem far-fetched ideas.

Although science describes the biological targets and their potential benefits on weight loss, one has to remember that the expensive drugs designed to activate BAT will obviously come with side effects in long term.

Most of the studies focussed on BAT activation are animal studies or proven to be effective only in those who already have brown fat tissue. Researchers also present concerns of increased appetite and excessive perspiration as a result of activated BAT.

If the researchers crack the code of browning white fat or increasing brown fat without side effects, it would be a dream come true. But till then its best to stick to old school methods of weight loss.

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