more than 50% of Americans have a weight problem.
Correct. The same is the case in Australia (and maybe the UK?)
Here,
overweight is defined as having a Body-Mass Index of over 24.
HANDY TIP TIME Your BMI is a loose (note, loose) indication of the ratio of your mass to your height. Here's how you calculate it:
BMI = M/(h^2)
Where M is your mass in kilograms, and h is your height in meters (yes, the world runs on metrics).
For adults (if you're not an adult you should expect to get slightly lower values):
<20 is underweight
20-24 is considered healthy
24-27 is considered slightly overweight
27-30 is considered moderately overweight
30+ is considered obese.
There are exceptions to this, though. Some people are naturally heavier than others and not necessarily any
fatter. George Clooney, for example, had a BMI of 30 at one point and he certainly didn't look it. Muscle is also heavier than fat, so if you're ripped (like Arnie used to be), you can also expect a BMI around the 30+ range. But these aren't particularly common exceptions.
These days though, we're (I mean doctors, of which I am not actually yet one) are having to define classes of obesity due to the rise in number of cases of people having BMIs of waaaaay over 30. For example we consider 40+ to be "morbidly obese"...a BMI of 60 is "super super obese" at which point, I do have to ask. What's the point?
Note that these values are not entirely stable. They're based on normals which is largely defined by the population. So too is risk (as risk is a relative thing), so at this rate, I expect to see these values rise...which means that my BMI of 21 (being a lean-mean kung-fu machine) may soon be considered "underweight", to which I say pish!