Matt and I are currently working on updating the What is a Healthy Weight? chapter. In the current chapter we state;
“The actual average change in bodyweight for the majority of people during this “epidemic” has been about 6 to 10 pounds.” referencing the following paper;
Campos, P. et al (2006). The epidemiology of overweight and obesity: public heath crisis or moral panic? Int. J. Epidemiol; 33(1): 55-60
the full text is available HERE
Here is the paragraph for which we referenced;
“The claim that we are seeing an ‘epidemic’ of overweight and obesity implies an exponential pattern of growth typical of epidemics. The available data do not support this claim. Instead, what we have seen, in the US, is a relatively modest rightward skewing of average weight on the distribution curve, with people of lower weights gaining little or no weight, and the majority of people weighing ∼3–5 kg more than they did a generation ago.3 ” (p.55)
The paper that Campos et al references to support their 3-5kg (about 6 to 11 pounds, which we incorrectly stated 10lbs) is;
Flegal, KM. et al (1998). Overweight and obesity in the United States: prevalence and trends, 1960 – 1994. Inter J Obesity; 22: 39-47
the full text is available HERE
The challenge we are having is figuring out how Campos et al was able to ascertain the 3-5kg figure from the Flegal paper.
I sent Paul Campos an email 4 days ago (June 24, 2014) asking him how they were able to get to the 3-5kg figure from the Flegal et al paper. I have not heard back from him yet. He is likely busy and may not have had the time to get to my email yet, and will respond soon with information that makes it clear. I am an optimist. But, I also have a pretty strong feeling I will not get a response. I feel this way because currently I don’t see how the Flegal et al paper supports that statement. But time will tell.
For those of you interested, please look at these papers and let us know if we are missing something in the Flegal et al paper that would allow for such a specific range of weight gain to be ascertained from the data presented. Currently we feel that it is NOT possible to say from the data presented in the Flegal et al paper that the majority of people have gained about 6 to 10 pounds over the past few decades. The main reason we feel this way is the fact that people are categorized by BMI category (i.e., overweight, obesity, etc) and there is a fairly wide range of weights a specific person can have and still be in a particular category.
I did compile a few numbers, based on BMI classifications, to try to get a handle on this. To see what could be the amount of weight an individual could gain to move from one category, say overweight (25 to 29.9) to obesity (class 1- 30-34.9) I used the average heights of women and men, 5-4 and 5-10, respectively, for the examples.
|BMI – Overweight category|
|5-4||146 lbs||174 lbs|
|5-10||174 lbs||208 lbs|
A person who is 5-4 could weigh anywhere between 146 and 174 lbs (a 28 lb range) and a 5-10 person could weigh between 174 and 208 lbs (a 34 lb range) and be classified as overweight.
Will extend the example to include the BMI category of Obesity- class I
|BMI – overweight range||BMI – obesity – class 1|
|5-4||146 lbs||174 lbs||175 lbs||203 lbs|
|5-10||174 lbs||208 lbs||209 lbs||243 lbs|
For a person in the overweight category to move to just-over-the-line and have a BMI of 30, and be classified as Obese could gain the following amount of weight;
If 5-4, a person could gain 25 lbs (moving from a BMI of 25 ) to only 1 lb (moving from a BMI of 29.9) to then have a BMI of 30 and be considered obese.
If 5-10, a person could gain 35 lbs (moving from a BMI of 25) to only 1 lb (moving from a BMI of 29.9) to then have a BMI of 30 and be considered obese.
Let’s take this one step further, and use the full range of Obesity, class I (BMI 30.0 – 34.9), to see what the potential weight gain could be to still be able to state that a person moved from the overweight category to the obese category. Obviously the obesity range has two more classifications, but the majority of people in the obese range are in the Class 1 section.
If 5-4, a person could gain 57 lbs if they went from a BMI of 25 (146 lbs) to a BMI of 34.9 (203 lbs), which means a range of 1lb to 57lbs
If 5-10, a person could gain 69 lbs if they went from a BMI of 25 (175 lbs) to a BMI of 34.9 (243 lbs), which means a range of 1lb to 68lbs
In general, we could say that a person could move from the overweight to obese (class I) category by gaining as little as 1 lb or as much as about 70 lbs.
Additionally, in the examples above, the Obese II (BMI 35 – 39.9 ) and Obese III (> 39.9, morbid obesity) categories were not considered. This is potentially important because as a percentage of increase within a specific category, it is these categories that have had the largest increase (Flegal et al; CDC). Even Campos et al ackowledge this fact, by stating;
“While there has been significant weight gain among the heaviest individuals4… ” (p.55, emphasis is mine)
Finally, I think the following chart from;
gives a good visual of the trend of weights in the US since 1960.
With that all said how do we know, based on the data in the Flegal et al paper, that a “majority of people weighing ~ 3-5kg [6.6 to 11 lbs] more than they did a generation ago”?
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