Caffeine & Obesity: Scientists Explore Impact on Brown Fat

[Ygggdrasil]

Scientists studying obesity have had great interest in brown fat, adipose tissue that actually helps burn fat (for example, to generate body heat in the cold). Studies suggest that higher levels of brown fat correlate with lowered risks for obesity and diabetes, and scientists are studying whether activating brown fat might help in the fight against obesity. Nature recently published a paper showing that the signaling molecule adenosine activates the energy-burning function of brown fat by binding to A_2A receptors on the brown fat cells. Here's the abstract for the paper:

Brown adipose tissue (BAT) is specialized in energy expenditure, making it a potential target for anti-obesity therapies. Following exposure to cold, BAT is activated by the sympathetic nervous system with concomitant release of catecholamines and activation of β-adrenergic receptors. Because BAT therapies based on cold exposure or β-adrenergic agonists are clinically not feasible, alternative strategies must be explored. Purinergic co-transmission might be involved in sympathetic control of BAT and previous studies reported inhibitory effects of the purinergic transmitter adenosine in BAT from hamster or rat. However, the role of adenosine in human BAT is unknown. Here we show that adenosine activates human and murine brown adipocytes at low nanomolar concentrations. Adenosine is released in BAT during stimulation of sympathetic nerves as well as from brown adipocytes. The adenosine A2A receptor is the most abundant adenosine receptor in human and murine BAT. Pharmacological blockade or genetic loss of A2A receptors in mice causes a decrease in BAT-dependent thermogenesis, whereas treatment with A2A agonists significantly increases energy expenditure. Moreover, pharmacological stimulation of A2A receptors or injection of lentiviral vectors expressing the A2A receptor into white fat induces brown-like cells—so-called beige adipocytes. Importantly, mice fed a high-fat diet and treated with an A2A agonist are leaner with improved glucose tolerance. Taken together, our results demonstrate that adenosine–A2A signalling plays an unexpected physiological role in sympathetic BAT activation and protects mice from diet-induced obesity. Those findings reveal new possibilities for developing novel obesity therapies.

(Gnad et al. 2014. Adenosine activates brown adipose tissue and recruits beige adipocytes via A_2A receptors. Nature. Published online 15 October 2014. http://dx.doi.org/10.1038/nature13816 ).

These results are important because they suggest that drugs targeting the A_2A receptor (or some of the downstream signalling pathways) could help fight obesity. Indeed, obese mice treated with drugs that activate the A_2A receptor showed weight loss and improved glucose toleance.

The study, however, has potentially troubling implications. Caffeine is an A_2A antagonist, meaning that it prevents activation of the A_2A receptor. The results of the paper would then suggest that caffeine should inhibit energy metabolism by brown fat, negating its beneficial effects. Although the paper shows that A_2A antagonist do indeed block energy expenditure by brown fat, it does not look at caffeine specifically. Given the widespread consumption of caffeine, this seems like an issue warranting further study.

A quick web searched turned up this news article linking coffee consumption and obesity, but it suggests that the polyphenols in coffee are to blame, not caffeine. Does anyone else know of any studies looking at the relationship between caffeine consumption and obesity?

 

[Greg Bernhardt]

Very interesting. I don't have any amazing insight to add, but just that every day it seems the old adage of "everything in moderation" really is the best advice.

 

[Evo]

Why is everything good bad?

 

[256bits]

I was under the impression that caffeine consumption increased the metabolic rate.
It could be from this study years a few years back ( although I did not read the original but a news or magazine synopsis back then )
.http://www.ncbi.nlm.nih.gov/pubmed/2388099

Do not diet suppliments exist for athletes, or those so inclined, to take for weight loss, as an increase in thermogenesis? They must have gotten the idea from somewhere at sometime.

there is this study also, on mice, showing less fat with mice fed suppliments,
Anti-obesity effects of epigallocatechin-3-gallate, orange peel extract, black tea extract, caffeine and their combinations in a mouse model
.https://rucore.libraries.rutgers.edu/rutgers-lib/21311/PDF/1/
http://www.sciencedirect.com/science/article/pii/S1756464609000383

 

[SteamKing]

Why is everything good bad?

Just wait a few days: the bad stuff will be found to be unexpectedly good for you.

 

[Drakkith]

Why is everything good bad?

A good dose of Drakkie-poo is good for everyone, Evo.

The study, however, has potentially troubling implications. Caffeine is an A2A antagonist, meaning that it prevents activation of the A2A receptor. The results of the paper would then suggest that caffeine should inhibit energy metabolism by brown fat, negating its beneficial effects. Although the paper shows that A2A antagonist do indeed block energy expenditure by brown fat, it does not look at caffeine specifically. Given the widespread consumption of caffeine, this seems like an issue warranting further study.

Wow... glad I cut back on my caffeine...

 

[Ygggdrasil]

I was under the impression that caffeine consumption increased the metabolic rate.
It could be from this study years a few years back ( although I did not read the original but a news or magazine synopsis back then )
.http://www.ncbi.nlm.nih.gov/pubmed/2388099

Do not diet suppliments exist for athletes, or those so inclined, to take for weight loss, as an increase in thermogenesis? They must have gotten the idea from somewhere at sometime.

there is this study also, on mice, showing less fat with mice fed suppliments,
Anti-obesity effects of epigallocatechin-3-gallate, orange peel extract, black tea extract, caffeine and their combinations in a mouse model
.https://rucore.libraries.rutgers.edu/rutgers-lib/21311/PDF/1/
http://www.sciencedirect.com/science/article/pii/S1756464609000383

While the study, in a vacuum, suggests that caffeine should prevent brown fat from burning energy, caffeine could also have other effects that counteract its effects on brown fat. Caffeine acts as a fairly broad spectrum adenosine receptor antagonist, not only targeting A2A receptors but other receptor subtypes as well. Because these receptors are present all throughout the body (including in the brain which explains caffeine's effects on wakefulness), it is certainly plausible that caffeine's effects on other parts of the body could lead to increased metabolic rate. As with all studies of diet, it is often difficult to get a conclusive answer from observational studies. Greg's advice of everything in moderation may be the best message to take.

 

[bohm2]

I was under the impression that caffeine consumption increased the metabolic rate.

How about the combination of nicotine and caffeine:

Effect of chewing gum containing nicotine and caffeine on energy expenditure and substrate utilization in men
http://ajcn.nutrition.org/content/77/6/1442.full.pdf

Cigarette Smoking, Nicotine, and Body Weight
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3195407/pdf/nihms-326984.pdf

I always wondered why nicotine wasn't marketed as a weight loss supplement/medication because it seems there is arguably more safety data than other weight loss products and the effect on weight loss (regardless of exact mechanism) appears to be pretty robust.

 

[mrspeedybob]

As a prodigious consumer of caffeine with a gradually expanding abdomen, I find this disturbing...
Awaiting more conclusive results.

 

[Physgeek64]

I don't think I could live without my coffee everyday! but at the same time it'd be nice to shed a few pounds! why caffeine, why?

 

[Doug Huffman]

Research for ill effects from caffeine epitomizes research until the desired conclusion is effected. Quite similar to the health effects of low level ionizing radiation and low level RF EM fields. Hormesis, it's not the drug but the dose.

Apropos shedding pounds, I am just home from a ten mile 'bicycle' (recumbent trike) ride that started in 45°F and ended at 45°F. But the fall colors, a week past peak, are still spectacular.

 

[redrenegade]

Very interesting. I don't have any amazing insight to add, but just that every day it seems the old adage of "everything in moderation" really is the best advice.

For being in the computer age . Or age of technology. All I heard today was " My computer is running slow" bare with me.

 

[Borek]

As a prodigious consumer of caffeine with a gradually expanding abdomen

After reading the post I wanted to check who wrote it, and I misread your nick as mrspeedyblob.

 

[redrenegade]

All that comes to mind about caffeine and obesity. First thought is a cup of coffee. And say back in the 1970's it was just that a cup of joe. Today society has run rampant on marketing coffee . Via shops , pods , beans , machines, flavored .
Coffee in itself has very few calories. Truckers would drink it on the road black to stay awake. Nowadays that caffeine fix can have as many calories as a Big Mac.
Just an observation .
Thank you

 

[DrDu]

I always thought brown fat is only present in hibernating animals? So are these findings really relevant to man?

 

[Ygggdrasil]

I always thought brown fat is only present in hibernating animals? So are these findings really relevant to man?

Although the presence and relevance of brown fat in adult humans has been a subject of debate, in 2009, three independent groups published papers in the New England Journal of Medicine confirming that brown fat is present and active in adult humans. From the editorial accompanying the papers: "The common message from these studies is that brown adipose tissue is present and active in adult humans, and its presence and activity are inversely associated with adiposity and indexes of the metabolic syndrome." (http://www.nejm.org/doi/full/10.1056/NEJMe0900466) So substances that alter the activity of brown fat can potentially influence the metabolism of man (and woman).

How relevant these particular findings are with regard to the effect of caffeine on obesity is less clear. As I noted in a post above, caffeine has a number of effects on many different body systems, so even though caffeine likely inhibits energy burning by brown fat, its effects on other tissues could counteract (or enhance) this effect. Observational studies looking for a link between caffeine intake and obesity seem to give mixed results.