Posts Tagged ‘BMI’

Does a pound of apples equal a pound of potatoes?

Wednesday, May 22nd, 2013

In January, 2013 a rather startling article in JAMA concluded that its not only okay, but actually may healthier, to be somewhat overweight and it’s not bad to even be a little obese.

That conclusion took many of us by surprise and was hard to swallow. I read it and went into my hypercritical mode.

To start with almost everyone would agree that those who are really skinny may not be healthy, unless they’re a marathon runner or some other kind of well-trained athlete. And, by the same token, being truly obese is bad for you.

But why should people who are overweight be healthier than those of us who are reasonably trim? And, to step things up a notch, why should being mildly fat not carry some risk?

This was a meta-analysis which an online dictionary  defines as a systematic method that takes data from a number of independent studies and integrates them using statistical analysis.

In other words, the authors weren’t doing their own large prospective study (one that starts at the current time and follows a group of research subjects over a {hopefully} extended period of time) but was a project that (retrospectively) reviewed the past work of others.

The gold standard in medical research, from my reading, is to have a randomized, controlled, double-blinded, prospective study. That translates into the research subjects being allotted by a method that picks them in a non-biased fashion to some kind of treatment or another (or none) and neither the researchers or the “researchees” know what group they’re in. Ideally the total number of subjects should be quite large and the study starts when they’re chosen and goes on from there.

Here there wasn’t a treatment and it was reasonable to look at other authors’ work done in the past, but of course there are hazards in doing so. What often appears to happen, is a group of researchers say, “Let’s look at problem X by seeing what other medical scientists have done. And we’ll accept or not accept those previous studies by criteria we can agree upon.”

These authors retrospectively examined data from 97 studies including nearly three million subjects (2.88M), but those came from a pool of over 7,000 articles and excluded, for pre-set and logical reasons, 98% of those.

In the same edition of JAMA were comments in a superb editorial piece, “Does Body Mass Index Adequately Convey a Patient’s Mortality Risk,” It mentioned a 1942 statistician working (as my Grandpa Sam did) for the Metropolitan Life Insurance Company said staying at the same weight you were at at age 25 meant you had a better chance for a longer life. Later on height and weight tables were compiled and a number called the body mass index could be derived using those two measurements and, in general, the CDC said, it was a reasonable estimate of how lean or chubby you were.

Normal BMI is said to be between 18.5 and 25 (I’m at 21 at present), so underweight would be represented by those with a BMI <18.5, the overweight range is 25-30, low-grade obesity from 30 to 35, grade 2 obesity from 35 to 40 and grade 3 obesity from 40 on up.

Since the origin of the concept behind BMI was European (by a Belgian polymath somewhere between 1830 and 1850), it’s usually measured as the weight of a person in kilograms divided by their height in meters squared. A close American version is weight in pounds divided by height in inches squared and then multiply by 703.

So at 150 pounds and 71 inches tall (I’ve lost at least a half an inch over the years), my BMI calculates as 20.9. If I weighed 200 pounds, my BMI would be 27.9 and I’d be called overweight. At the most I’ve ever weighed (216) and with my younger height of 71.5 inches, my BMI was 29.7. That’s a 66 pound difference; I thought I was fat at that weight.

Total mortality, the editorial said, has a U-shaped relationship with BMI, with considerably higher risk of death at BMI’s less than 18.5 or greater than 30.

That’s long been the traditional viewpoint, but the data in the January JAMA article didn’t seem to agree with the latter finding. The editorial clarified matters considerably, saying the normal range can be divided in two parts with those having a BMI between 18.5 and 22 having a higher mortality rate than those who BMI is between 22 and 25.

I’d go a step further by saying there are those of us who have a relatively low BMI because we’re lean and exercise a lot and others who have a similar BMI because of chronic illness or poor nutritional intake.

Lean and well-muscled

Lean with a muscular torso

I have well-muscled legs (I ride a recumbent bike for 15+ miles and 500+ calories six days a week), but I’ve never had strong arms and I’m small-boned. Since the beginning of 2009 when I went back on my own eating plan and really increased my exercise time, I’ve gone from a 38 inch waist to 33 and given away slacks and belts. If I weighed 200 pounds and was a large-boned guy with a great torso and a small waist, I think my risk factors for death would be less than if I had a big belly and weighed the same 200 pounds.

So we need to add waist measurement and probably blood pressure, blood lipids (HDL cholesterol and triglycerides) and fasting blood sugar to the BMI to get a better estimate of risk factors for dying.

That still doesn’t explain why those with a BMI of 30 to 35 appear to do well. One comment is that docs have gotten considerably more aggressive in looking at and managing blood pressure, lipids and elevated blood sugars in those of their patients who are overweight or obese.

Weighing what I do now, down nearly 30 pounds since early 2009, my own physician hasn’t suggested I get a fasting blood sugar or a lipid panel for several years.

I bet she would if I weighed 216 again.




Adults, obese and otherwise

Sunday, February 12th, 2012

PIck well and cut back your waste/waist

In my last post I explained the concept and the math behind the body mass index (BMI) approach to evaluating if your weight was normal or not (your BMI is very  well in synch with the most scientific methods of determining body fat percentages). Now I want to expand on that a bit  with some recent statistics and some thoughts on how we can lose weight if we need to. Unfortunately, some of us have lots of extra pounds we should shed if we want to have our best shot at leading long, healthy lives.

The Feb 1, 2012 issue of JAMA had a number of interesting articles on obesity. I’ve previously mentioned several on childhood and adolescent obesity; today I’d like to zero in on two whose focus is American adults.

Four CDC staffers, led by Katherine Flegal, PhD, published the most recent statistics from a recurring national survey with the daunting acronym NHANES. This national health and nutrition survey (the E stands for examination) started in 1971, but from 1999 on has been released results in two-year cycles. The current article from the National Center for Health Statistics, looking at the 2009-2010 NHANES data had a little good news and lots of bad news.

After 1980, until the turn of the 21st century, the prevalence (scientific term for percentage) of obesity in our population kept zooming up. Now it appears to have leveled off. I guess that’s something we should be happy about, except now over 35% of adults in this country are obese. Men and women have about equally high rates of obesity and men have caught up to women in this regard over the last twelve years. Some subsets, by sex and racial groups, are even more likely to be obese or very obese.

The worst news from this article was that no group–men, women, non-Hispanic whites, Hispanics or non-Hispanic blacks–had a decrease in the prevalence of obesity in this most recent data set.

So which exercise and diet should we try?

getting enough exercise is difficult when your joints hurt

Many adults report “No Leisure-Time Physical activity.” Overall, more of us are exercising, but the data vary from state to state. Those who have arthritis, fifty million in the US, need special attention or are even more likely to get no exercise. The CDC has worked with the Arthritis Foundation to develop ideas for this huge group. Going back to my review of articles on youngsters, I think for the rest of us, we could begin with simple steps, parking at the far end of the parking lot and substituting some walking for part of our screen time as two examples.

Harvard Medical School’s free online HEALTHbeat publication had a review of pros and cons of various diets in its Feb 7, 2012 edition. The bottom line still is if you want to lose weight, you must cut down on your calories. The Mediterranean-style emphasis on fruits and vegetables, unrefined carbohydrates, nuts, seeds and fish may be the most effective in reducing cardiovascular and diabetic risks.

My New Year’s Resolution is to keep my weight under 150 pounds. I have to work at it as I like to eat, but most of the time I’ve stayed away from splurges.

How about you?





Adulthood: when your BMI is more important than your IBM (stock)

Thursday, February 9th, 2012

I do this at home, without clothes

In my last post I wrote about our upcoming generations and their obesity issues. Unfortunately, as you might have easily been able to predict, that carries over into adulthood. The same issue  (Feb 1, 2012)  of the Journal of the American Medical Association (usually called JAMA) had several articles on adults also. To begin with the National Health and Nutrition Survey (NHANES) looked at the body mass index (BMI) of men and women from 1999 through 2010.

“AARRGGHH” you say, “Why the hell should I care about whatever BMI is enough to try to understand it?”

Well, that’s a tough question, I admit. But BMI is the standard way of deciding if a person is too thin, normal, overweight or obese. So let’s give it a try.

Your BMI is a number calculated using your height and weight.  If you weight 250 pounds and you’re a seven-foot tall basketball professional center player, you’re unlikely to be obese. But if you’re five foot, six inches tall, and don’t exercise at all, like the adolescent I was reading about recently, you’re far too heavy. In the first case, the athlete has a lot of muscle, whereas the youngster is almost certain to be carrying around a lot of excess fat.

For a long time physicians just weighed their patients. That plus eyeballing their bodies in an exam room works for most people. Then along came the BMI as one way of getting a little more scientific. I looked online for the history of the use of body mass index as I suspected it was “invented” by a European (it was). It certainly seems to me to favor the metric system. There it’s easy to figure out your BMI; you divide your weight in kilos by your height in meters. It’s much more complicated using pounds and inches (BMI = weight in pounds divided by height in inches squared and that number is multiplied by 703) The CDC explanation of BMI is helpful and also supplies a “widget” you can download and a calculator if you just want to bookmark the website.

height counts, for adults too

So now you’ve (hopefully) figured out your own BMI; What does it mean and how reliable is it?

First the numbers: most people with a BMI under 18.5 are skinny, underweight. That probably excludes a whole passle of long-distance runners. Most people with a BMI over 18.5 and under 25 are in the “normal” weight category. I used the CDC calculator and my number is 20.5. Most whose magic number is 25+ and less than 30 are overweight and almost anyone whose BMI is over 30 is obese. The teenager I mentioned above has a BMI of 40.

Okay, you say. Now what do I need to do once I know what category I’m in.

I’d start with the eyeball test. Do you have a roll around the middle? In early 2009, weighing only three pounds more than I had for twenty years, I clearly did. I made up my mind to do something about that excess flab, knowing that fat in the belly also implies arteries that are narrowing down.

After losing thirty pounds and keeping it off, I bounced up after the Superbowl and went back on my diet, i.e., consuming fewer calories. I went to a meeting last evening; there were lots of goodies, but I ate only carrots and cucumbers. This morning I’m at 148.2 pounds, smack dab in the middle of the three-pound “ideal weight” range I decided on.

Harvard Medical School just published a piece titled “Choosing the diet that will work for you.” The central theme is cutting calories.