Underweight & correlation to life expectancy

[wildcat]

Hey Rich, I have read and watched different studies on this topic. Apparently, some doctors/researchers think being underweight adds to your life expectancy while some believe it detracts from it. I can't tell who is right.

I saw this on some news show - dateline, 20/20 or something. The underweight theory was applied to some lab rats. They fed them small portions and kept them slighty underweight. They lived quite a quite a bit longer than the other rats - normal & overweight. So they believe the results could be applied to humans and a bunch of people signed on to be monitored. The people who signed on looked pretty frail (and I think they used the BMI as a reference for weight which I think is flawed) but they were all in excellent shape on the tests they ran.

But I have also read that being underweight does not add to your life expectancy. That it is good to have some fat on your body - a normal, average body type I guess is the best in terms of longevity.

Any thoughts on this? I am sure there are numerous other factors that should be analyzed but I am curious nonetheless.

Full disclosure ---- I am not changing my eating habits

[Patrick]

Dr. Roy Walford of UCLA has been a proponent of caloric restriction while maintaining sufficient nutrition. He has written several books on the topic, "The 120 Year Diet" being one of them. He has conducted many experiments with rats similar to the one you cite. It is very difficult to get adequate nutrition with reduced calories, so he has a computer program to help figure out menus.

http://www.walford.com/

[Sheryl]

Both are interesting topics. but to me there is a significant difference between being "underweight" and being on a severely calorie restricted diet.

Many people can eat a reasonable number of calories, and with reasonable levels of excercise still remain well under the "recommended" weights like these.

http://tinyurl.com/4568g

The inerrelated factors of genetic (or hereditary) predisposition, high metabolism, frequent excercise, healthy eating, less strain on skeleton and organs, etc., would all have to be controlled for in order to find out if it's really the quality of being underweight that is contributing to improved health.

Edit: But I'm not Rich.
(Although I am wealthy)

[haha]

Quote:

Originally Posted by Patrick Dr. Roy Walford of UCLA has been a proponent of caloric restriction while maintaining sufficient nutrition.

Perhaps you mean Dr. Walford had been a proponent...

http://en.wikipedia.org/wiki/Roy_Walford

[Patrick]

Quote:

Originally Posted by HaHa Perhaps you mean Dr. Walford had been a proponent... http://en.wikipedia.org/wiki/Roy_Walford

Well apparently his program wasn't too successful for him . . .

[Sheryl]

Quote:

Originally Posted by Patrick Well apparently his program wasn't too successful for him . . .

Yeah, ALS is not conducive to longevity.

[wabmester]

If you look at BMI, there is a J-shaped mortality curve, meaning all-cause mortality increases for both fat people and skinny people. This is true even after correcting for smoking and chronic diseases.

The optimal BMI for men in terms of lowest mortality was between 23-25.

Here's a study that just looks at skinny people (BMI around 20):

link

The characteristics of participants with a BMI below 18 kg/m2 were favourable to a lower risk of cardiovascular disease. Nevertheless, these participants had an increased all cause death rate ratio (2.07, 95% CI 1.58 to 2.70) in comparison with participants who had a BMI between 20 and 22 kg/m2. The death rate ratio for the slimmest category was also significantly increased for circulatory diseases (including ischaemic heart disease and cerebrovascular disease), respiratory diseases, and all other causes combined excluding all malignant neoplasms. This finding was consistent across a range of subgroups.

[Nords]

Quote:

Originally Posted by Patrick It is very difficult to get adequate nutrition with reduced calories, so he has a computer program to help figure out menus.

Quote:

Originally Posted by HaHa Perhaps you mean Dr. Walford had been a proponent...

One data point is that Walford subjected himself to that diet for at least 10 years... and died due to ALS complications. But AFAIK he was a CR adherent to the day he died.

However the precedent is kinda like all the controversy surrounding Atkins' demise. If we don't know what causes ALS and if we can't prove that Atkins diets don't cause cardiac issues... then perhaps the risks outweigh the rewards.

Quote:

Originally Posted by wab Nevertheless, these participants had an increased all cause death rate ratio (2.07, 95% CI 1.58 to 2.70) in comparison with participants who had a BMI between 20 and 22 kg/m2. The death rate ratio for the slimmest category was also significantly increased for circulatory diseases (including ischaemic heart disease and cerebrovascular disease), respiratory diseases, and all other causes combined excluding all malignant neoplasms. This finding was consistent across a range of subgroups.

I think that what the researchers are trying to say is that the skinniest people had clearly lost the will to live!

I don't mind cutting out the second serving of chocolate ice cream and I can even stand cutting back on the size of the serving. But I won't cut it out completely!

[Patrick]

Quote:

Originally Posted by Nords However the precedent is kinda like all the controversy surrounding Atkins' demise. If we don't know what causes ALS and if we can't prove that Atkins diets don't cause cardiac issues... then perhaps the risks outweigh the rewards.

I thought Atkins died when he slipped on an icy sidewalk and cracked his head.

[Khan]

Quote:

Originally Posted by wab If you look at BMI, there is a J-shaped mortality curve, meaning all-cause mortality increases for both fat people and skinny people. This is true even after correcting for smoking and chronic diseases. The optimal BMI for men in terms of lowest mortality was between 23-25. Here's a study that just looks at skinny people (BMI around 20): link The characteristics of participants with a BMI below 18 kg/m2 were favourable to a lower risk of cardiovascular disease. Nevertheless, these participants had an increased all cause death rate ratio (2.07, 95% CI 1.58 to 2.70) in comparison with participants who had a BMI between 20 and 22 kg/m2. The death rate ratio for the slimmest category was also significantly increased for circulatory diseases (including ischaemic heart disease and cerebrovascular disease), respiratory diseases, and all other causes combined excluding all malignant neoplasms. This finding was consistent across a range of subgroups.

These studies never seem to indicate if the high BMI was fat or muscle.

[Khan]

Quote:

Originally Posted by Patrick I thought Atkins died when he slipped on an icy sidewalk and cracked his head.

He did.

He was on life support for a while and swelled up from the fluids; then PETA stole his medical records and said he was obese from eating meat.

http://www.snopes.com/medical/doctor/atkins.asp

Yet according to a copy of his medical records, as turned over to USA Today by the diet guru's widow, Atkins weighed 195 pounds upon admission to the hospital 8 April 2003 following his fall.

[wabmester]

Quote:

Originally Posted by Khan These studies never seem to indicate if the high BMI was fat or muscle.

The study I read a while back looked at death records for a *lot* of people. Over 100,000. I doubt that a few body-builders would effect the results much. Most people with a high BMI are fat.

Edit: here's one study that looked at over 1 million people:

link

[Sheryl]

Quote:

Originally Posted by wab Edit: here's one study that looked at over 1 million people: link

Yay. I'm right at the low point of the J.

Note the first study referenced seemed to be about non-meat eaters, specifically. That could be a whole different can of worms tofu.

[wildcat]

http://www.nhlbi.nih.gov/health/publ...se_wt/risk.htm

BMI is a reliable indicator of total body fat, which is related to the risk of disease and death. The score is valid for both men and women but it does have some limits. The limits are:

It may overestimate body fat in athletes and others who have a muscular build.
It may underestimate body fat in older persons and others who have lost muscle mass.

So BMI doesn't just affect the muscle heads, old people as well. This is where I get fuzzy with all of the data and its true meaning. What would be the outcome of a person losing a lot of weight vs. a person staying pretty lean & muscular for his/her age but the BMU indicated otherwise? I still believe the life expectancy is 60-70% genetics and 30-40% other but I could be wrong.

[wabmester]

Quote:

Originally Posted by wildcat I still believe the life expectancy is 60-70% genetics and 30-40% other but I could be wrong.

That's what I used to think, but twin studies suggest that it's more like 30% genetic, 70% lifestyle.

Maybe one of the docs can chime in here, but I don't think mechanisms are very well known. It looks like a lot of body fat is bad for you for at least three reasons:

1) Fatty plaques are more likely to form in your arteries (heart disease)
2) Fat is more likely to marble your organs and screw up their function (e.g., fatty liver and diabetes)
3) Fat seems to be associated with cancer, probably as a tumor growth promoter

So, by being skinny you avoid these problems. But thinness also seems to be associated with frailty, respiratory disease, etc.

The key to long healthy life seems to be physical fitness + being not too fat.

Take a look at one of the standard fitness charts (like the Navy's) and see how you rank in terms of push-ups, VO2max, etc.

[Khan]

Quote:

1) Fatty plaques are more likely to form in your arteries (heart disease) 2) Fat is more likely to marble your organs and screw up their function (e.g., fatty liver and diabetes) 3) Fat seems to be associated with cancer, probably as a tumor growth promoter So, by being skinny you avoid these problems. But thinness also seems to be associated with frailty, respiratory disease, etc. The key to long healthy life seems to be physical fitness + being not too fat.

Strive to be lean and mean. 8)

[excellent]

Full nutrient intake along with a slight hit to the normal amount of total Kilocalories taken in increased the average life expectency of lab mice, not the life span. Life expentency is the average expected lifespan of an organism, life span is the longest an organism can be expected to live. For humans the life span hasn't gone much above 100, while expectency has been growing (albeit there might be a rapid drop when the obese of today begin to reach their nigh years). Also, life expectency and quality of health is much more lifestyle related than genetics... predisposition to certain diseases in no way means that you cannot prevent the triggers with some good old fashioned diet and exercise.