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AF Association
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Sheep Study Lifts the Wool on Obesity as Cause of AF

Food for thought.



"It's easy to say two conditions are associated. Lots of things go together. It's much harder to claim one condition causes another.

In the US and other Western countries, obesity and atrial fibrillation are increasing in tandem. Ample evidence exists to associate the two diseases.

The question is: Does obesity cause AF? Or is it the other diseases that go with obesity, such as sleep apnea, hypertension, and diabetes? It's an important question because treatment (of any disease) is most successful when it targets the cause.

An elegant experiment [1] led by Dr Rajiv Mahajan (University of Adelaide, Australia) gets us very close to saying, yes, obesity does indeed cause AF.

As I tell you about this experiment, keep in mind what causes reentrant arrhythmia in the first place—multiple pathways, slowed conduction, and unidirectional block. In healthy cardiac muscle, conduction proceeds rapidly and smoothly through the cells; there is little chance of electrical reentry. In diseased muscle, inhomogeneity of conduction produces the milieu for reentry."

" The Study

The Australian research team compared electrical and structural cardiac properties of two groups of animals—obese (n=10) and lean (n=10) sheep. They created obese sheep by overfeeding. After 36 weeks of persistent obesity, researchers performed blood testing, echocardiography, electrophysiology testing, electroanatomic studies, and histology in both groups. They found significant differences:"

18 Replies

I'm sure there must be some truth in this. I wonder how many of us with AF are a little or more overweight? I must admit my AF only started when I put on just over a stone in weight. Any really slim people on here who have AF?



Yes. I've never been even mildly overweight.


Always been slim but I'm tall so heavier than average.


I'm tall too, so my excess fat isn't very noticeable.


If I wasn't depressed before I read this, I am now!


Plenty of skinny people with AF. Just look around at HRC! (Advert ---get your booking in NOW. )


Yes I have AF & I'm slim. ??????

Genetics. Two of my 4 Brothers have it also. ??????


I'm also slim and first had AF 20 years ago.

I weigh just under 10 stone and have a BMI of 20 and haven't varied much since my 20's.

I am sure those with AF must have a genetic disposition to getting it in the first place but then one or various other factors trigger the first event - being overweight is probable just one of those factors.


I've got a BMI of 24 which is the same as I've had for the last 50 years. Of the people I've met with AF, perhaps 20% were overweight. So for those who have AF and are overweight there's an obvious answer. For the rest of us, we are not so "lucky" in having such an obvious solution and ablations can be a real benefit.

I do wish John M would stop banging on about obesity and AF as though that is the only cause. However I do realise in the US obesity is an even greater problem than here in the UK.



So, there are several causes of AF just as there are several causes of heart disease, cancer etc. Some are genetic, some the result of injury, disease or lifestyle. On the other hand, not everyone who chooses a particular lifestyle gets a disease. Nor does everyone with a genetic predisposition become ill. Some people develop AF through over exercising and probably don't have a weight problem at all.

1 like

Hi Engmac - thank you for yet another interesting post.

Before I had my first ablation in 2009 at The Heart Hospital in London I was invited up for a pre- ablation talk & discussion with one of the consultant EP s. Among the many ablation patients attending I noticed that I was the only overweight patient ..... there were a few very fit looking young men I just happened to notice (?! ) ......

Nevertheless common sense tells us that being overweight is not good for any health aspect. Articles such as this are very motivational for those of us attempting to make life style changes.



Indirectly. Obesity can be caused by a high fat diet; a high fat diet can cause atheroma of the coronary arteries. Narrowed arteries can cause ischemia symptoms like pain and arrhythmias such as AF.


My B.M.I is 22 but when I first got A.F. I was overweight. I lost 4 stone but my A.F. got significantly and progressively worse. My left atria is not enlarged . I know that it can go back to its normal size. However following my recent ablation I know there was no fibrosis. So, although I was overweight and actually obese it doesn't appear to have given me A.F. as non of the A.F. giving factors were present. My blood pressure was fine and no diabetes or or sleep apnoea either. Further more, losing weight didn't improve things.

However I do feel much better slimmer and its got to be healthier in the long run. X


They fattened some sheep until they were at least twice a healthy weight and then induced afib. The fat ones took longer to come out of afib than the normal weight ones.

I do not agree with testing things on animals and I cannot see the point of doing so in this "experiment". Surely there must be enough information out there on this subject to reach a sensible conclusion without doing this.

I also object to them saying that obesity causes afib. It does not! The strongest word used should have been "CAN".

How many people with afib who are a little overweight will now be feeling guilty because they have caused their own problems? Afib on its own is enough to deal with without having stupid articles like this one adding guilt to the mix. ( I am am not overweight I'm 6'4" and weigh 15st.)

It would seem that there are some people who like to get attention for themselves by latching on to such results and sensationalising them. I'm sure the extra attention they get for themselves does not go un-noticed by sponsors. (Heavy sarcasm.)

The main lesson I take from this is that farmers should not overfeed their sheep if there are people around who can induce afib in them!

Rant over!



I am 5' 4" and 8 stone 10 lbs and have never been overweight but was diagnosed with AF last December, the only thing that I can think of that maybe caused mine is that I am a worrier and seem to stress myself out sometimes for no reason.


I am the perfect weight for someone who is 9' 6", unfortunately I am no where near that height.


I think researchers and doctors should read sites such as this AF Association site. They would probably gain some useful knowledge and the information gleaned could encourage them to listen to the patient more and maybe even influence them to make better treatment recommendations.

I am not overweight, never have been and have none of the usual health issues that should cause AF but I have it. There is still lots to learn about this affliction.


My weight ballooned after my AF diagnosis, I think due to any vigorous aerobic exercise bringing on AF. I still cycle as much as I can, that and swimming I seem to be ok. But boxing and kickboxing have had to go.

I'm 95kg and 6'2"

I'd like to get back to under 90

I am told my AF is likely genetic but brought on by drug abuse and years of heightened stress levels.


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