This article, written by an Australian researcher in epidemiology, starts out talking about how amazing it is that people (the world over) are fatter than ever and people (the world over) are living longer than ever, so maybe being fat is not going to impact trends in life expectancy.
Except then it goes on to make all kinds of guesses and predictions why this good news can’t last.
For fuck’s sake.
At least the author admits that the situation is complicated. It is complicated. May I suggest possibly too complicated to readily lend itself to guesses and predictions?
First the excuse that people (at least in the US) are living longer is because “cholesterol, smoking and physical activity have improved in recent years”, and that medical treatment has improved for conditions like hypertension. An increase in physical activity, as many studies have shown, can make a big difference in a person’s health (thin, fat, or in between), and that is a behavior that individuals can modify, unlike things that are affected by heredity (like cholesterol and type 2 diabetes).
But the author has to take a little wee in the Cheerios here. Proposing that the rate of decline in mortality might have been even faster except for “the increasing prevalence of diabetes”. Well, while type 2 diabetes is a risk factor for fat people, the American Diabetes Association website (http://www.diabetes.org/diabetes-basics/genetics-of-diabetes.html) tells us:
“Type 2 diabetes has a stronger link to family history and lineage than type 1, although it too depends on environmental factors. Studies of twins have shown that genetics play a very strong role in the development of type 2 diabetes.”
A study has shown that thin people with type 2 diabetes have higher mortality rates than overweight or obese people with the condition. http://jama.jamanetwork.com/article.aspx?articleid=1309174
The author then says:
The best estimates of the association between body mass index (BMI) and mortality suggest that the mortality risk from excess body weight increases from a BMI of 25 but isn’t substantial until BMI exceeds 32 or 35.
Well this is just wrong. Studies, including the latest one from the CDC published in JAMA January 1, 2013, have shown that the people with the least mortality risk of EVERYONE are people who fall into the overweight BMI (25-30) category. Furthermore, “Grade 1 obesity” (BMI 30 to < 35) is not associated with any greater risk of mortality. http://jama.jamanetwork.com/article.aspx?articleid=1555137
As the author points out very fat people are in the minority (estimated by her to be between 15% and 25% in the US); and she correctly points out that as we get older, low body weight puts you at a higher risk of disability and mortality.
And while the author does suggest “body weight may not be a significant risk factor for mortality in itself,” she goes on to say it may be a “surrogate marker” for a particular lifestyle, or a particular diet and physical activity level (to her credit, she admits that genetic factors also have an effect). To me that is just a polite way of saying that we’re fat mostly because we eat too much and we don’t exercise. She fails to add that being fat can be a marker of environmental effects, socio-economic effects, medication, disease or disability.
And, since studies are not showing that fatties are dropping like flies, we get to the latest “concern” for us fatties, that the “negative impact of recent obesity trends, including longer duration of living with obesity may not have yet affected life expectancy … And the adverse impact of obesity may be due to both its severity and duration” (emphasis added). Excuse me, but fat people have been around pretty much as long as people have been around; to suggest that people who have been fat over a long period of time is a new thing is just ridiculous.
Then the author claims that “for the first time in over 25 years, [there is] a slight decline in US life expectancy“. First off, “life expectancy” is a prediction or guess. Second, the most recent figures available from the CDC are as of 2011 and show life expectancy in 2011 remained the same as 2010 and a decline in over all US mortality rates. http://www.cdc.gov/nchs/data/nvsr/nvsr61/nvsr61_06.pdf
And while, WLS (weight loss surgery) may offer some positive cardiovascular benefits; the risks (including death) are many; and the weight regain rate is comparable to diets; and most cardiovascular benefits can be achieved through exercise whether or not there is weight loss.
Finally we get to the “obesity paradox”, where being fat seems to have some protective qualities. She has little to say about this except that it’s a “we don’t know” situation, which is fine. If you don’t know just say so. But she doesn’t stop at “I don’t know,” she also suggests that thin people may suffer more aggressive types of hypertension and diabetes. I would add, it’s also possible that the fat has a protective quality – but in both cases: WE DON’T KNOW.
The author does seem to be trying to give a balanced treatment of the question of whether obesity is a factor in life expectancy. But I feel the summing up shows a bias. Because the actual numbers have not borne out the idea that more fat people means shorter life spans overall, she proposes that the main impact is risk of becoming disabled (something that has not been discussed at all in the article and is totally out of the blue) or that life expectancy would be even better if not for all of us fatties.
By the way, the recent study she refers to in her “summing up” focused on the effect of fatness on mortality and disability in older people, and concluded that added weight was not shown to reduce life expectancy, but “was associated with a higher risk of becoming and remaining disabled”.
Without access to the complete study, I can’t say what was considered “disability”. Obviously, the term “disability” covers a huge range of types and levels of impairment. Having said that I think most people would agree they’d rather be on the right side of the grass, even if they have to deal with some level of disability.
This whole article is put forth in The Conversation, which bills itself as having “academic rigour, journalistic flair”, and is written by someone who is a “research fellow” in epidemiology. To me, a lay person, this seems to be a lot heavier on the journalistic flair than the academic rigour.
Torture numbers, and they’ll confess to anything. ~Gregg Easterbrook