Variously on this site, most recently here, I have reported on studies which show that being ‘overweight’ is associated with a reduced risk of death compared to having what would be generally taken to be a ‘normal’ or ‘healthy’ weight. The studies that show this association are based on the measurement known as the body mass index (weight in kg divided by the square of someone’s height in meters). The main problem with the BMI is that it tells us nothing about body composition. It is possible therefore for individuals to be fit, healthy and quite well-muscled, and to register supposedly elevated BMI values.
But recently a study has been published which suggests that the life-saving qualities of a raised BMI reading may not be down so much to muscle, but fat. The study, published on-line in the American Journal of Clinical Nutrition, looked at the relationship between a variety of body measurements and risk of death (mortality) as well as risk of illness (morbidity) in individuals aged 65 or more in a geriatric hospital in Paris, France [1].
Over time, the researchers discovered that having higher fat mass was associated with a reduced risk of mortality and morbidity.
For example, compared to the 30 per cent of people with the lowest fat masses, those with the highest 30 per cent of fat masses had a 70 per cent reduced risk of mortality, and a 75 per cent reduced risk of death or complications from their original illness.
There was, however, no significant association with other body measurements, including muscle mass, and mortality and morbidity.
This study suggests that bodily fat can be a bit of a lifesaver for elderly individuals. It has been suggested that fat provides a much-needed fuel reserve when individuals are struggling with a disease process that is ‘catabolic’ (i.e. body wasting) in nature.
The authors of this study also cite other studies which link, in the elderly population, lowered risk of mortality as body weight increases [2-4]. These studies, however used the BMI to assess weight, which as we know, tells us nothing about body composition. The interesting thing about this most recent study is that it suggests that it is increased body fatness that may confer benefit. More evidence is required to see if this turns out hold true for the elderly generally.
However, with the evidence as it stands, it seems that being ‘overweight’ from a BMI perspective is associated with reduced risk of death, and that in the elderly, being a bit chubby may confer health-related and survival advantages.
References:
1. Bouillanne O, et al. Fat mass protects hospitalized elderly persons against morbidity and mortality. Am J Clin Nutr 29th July 2009 [epub before print publication]
2. Landi F, et al. Body mass index and mortality among hospitalized patients. Arch Intern Med 200;160:2641-4
3. Mattila K, et al. Body mass index and mortality in the elderly. Br Med J (Clin Res Ed) 1986;292:867-8
4. Grabowski DC, et al. High body mass index does not predict mortality in older people: analysis of the Longitudinal Study of Aging. J Am Geriatr Soc 2001;49:968-79
When animals become ill, they naturally fast to conserve energy. This energy is diverted to healing. The organism continues to receive nourishment from its own stores. The greater the stores, and the more nutrient-rich they are, the longer the fast may go. Many acute life-threatening illnesses are recovered from and the body ecology is improved after this internal housecleaning.
I’ve seen this repeatedly in my cats when they get sick. They have fasted up to 8 days relying on their body stores. They curtail all activity and sleep. Several of my cats have recovered from various illnesses without any intervention at all.
Organs are rested and recover. Toxins are eliminated. Any food supply for bacteria is consumed and the bacteria die off. When the cats are finished fasting, they will eat small amounts several times a day until they bulk up again.
If they did not have the stores, they might not be able to fast long enough to overcome whatever their trouble is. Constant feeding of the sick is the road to ruin.
This study focused on the elderly. From my readings, for those under 65, there is a definite J-shaped curve. That is, those with the lowest body masses have a higher mortality risk than those with slightly higher body masses. But then as body mass increases (fat mass), mortality risk climbs again. Until you get to the over 65 population, then, as pointed out above, a small store of extra body fat can be protective.
Did this study make a distinction between intra-abdominal fat & fat stored in other areas of the body?
I have heard one commentator suggest that, for those who have large deposits of intra-abdominal body fat, they are often dead before they make up the 65+ cohorts!
This is a good summary & research update from the University of California:
http://www.uctv.tv/search-details.aspx?showID=16713&subject=health
Following up on Jamie’s comment, I wonder how to balance the idea that some fat is better, and the idea that abdominal fat is worse. I ask because I’m overweight and 66years old, but not obese, and I wonder how hard to work at losing weight, which is hard to do.
This actually happened to a friend of mine. She came home from North Africa with a bug and lost weight. She had been plump before her holiday and was now gaunt. Her doctor told her that her fat reserves were what had saved her life. If she had been a “Twiggy” she would have died.
Yippee! No more dieting for me!
I think it all depends on why someone is fat. Like a headache, maybe obesity is a symptin not a disease. For example if a perso s dat because they eat lots of junk food it would be the junk that causes the problems with heart etc. If it is low thyroid this in itself can cause problems. If it is fluid retention from food intolerance this is different again. Teaching adpation to children I have learned that animals who biologically and adpted to their environment and live in the cold like polar bears are fat and those living in the heat are slim. Where did the obese person’s ancestors come from?
PS Sorry about the typos.
All this reminds of earlier debates on this blog about the role of cholesterol as an out and out baddie (as cast by various government agencies etc). Why is it that our ability to survive has relied on being able to respond and adapt to environmental demands but now there is a ‘perfect’ and unchanging, ‘one size fits all’ measure to be found for all aspects of our biology? It seems that there is a lot of money to be made out of this search for perfection – or am I just being cynical?
There seems to be a pattern in several recent posts where many factors have a J curve – too little may be as dangerous as too much, just for a different reason.
It has been known for a very long time that studies that seem to show that higher BMI confers greater longevity, may in fact show no such thing when the unhealthy thin are removed from the calculations. The unhealthy thin include smokers and those suffering from chronic diseases – both of which tend to waste the body. The true test of BMI on longevity is to measure mortality outcomes in the healthy thin and the healthy fat.
last year i have so much Body fat because of a very bad diet and lack of exercise. now i am doing lots of Cardio to reduce the fat specially on my tummy.
Loved your article, the BMI or body mass index doesn’t give you an accurate picture of the health of an individual in most cases. At best the BMI will give you a very rough idea of where you stand in terms of your ideal weight to height ratios. Given that muscle weighs much more than fat, even extremely healthy individuals which have high levels of muscles mass can be labeled with a less than ideal BMI.
I think its is much more useful for a person to focus more on improving overall health than focusing on weight.