These different classifications are determined by body mass index (BMI), or a measure of body fat based on your height and weight.
To get a basic idea, this chart from the CDC approximates what that means for someone who is 5'9" tall.
As for what is driving America's chronic weight problem, there are no definite answers. Department of Agriculture (USDA) reports that the average American ate almost 20% more calories in the year 2000 than they did in 1983, thanks, in part, to a boom in meat consumption.
Scientific studies often reach conflicting conclusions, meaning many theories are out there, but the preponderance of evidence points to the two causes most people already suspect: too much food and too little exercise. Today, each American puts away an average of 195lbs of meat every year, compared to just 138lbs in the 1950's.
Other research suggests Americans burn 120 to 140 fewer calories a day than they did 50 years ago.
Add this to the higher amount of calories we are packing in, and we get a perfect recipe for weight gain. It is also how we get to work and what we do after.Too much food, too little exercise, and genetics top the list of reasons as to why the United States of America is the unhealthiest country compared to the rest of the world.Regardless of the exact cause of this phenomenon, obesity in the United States has become an epidemic.A number of other factors are thought to play a role in the obesity epidemic, such as the in utero effects of smoking and excessive weight gain in pregnant mothers.Poor sleep, stress, and lower rates of breastfeeding are also thought to contribute to a child's long term obesity risk.Another study demonstrates the full effect added sugars from soda and energy drinks are wreaking havoc on American waistlines. obesity epidemic is obviously major, but it's also complex.So it is not just how much we eat, but what we eat. Consumers are sent wildly mixed messages when it comes to what to eat and how much.While somewhat less sinister, added sugar can also wreak major damage on a diet.Technically low in calories, high-quantities of sugar disrupts our metabolisms, causing surges in insulin and energy levels and ultimately contributing to weight gain and diabetes.It's no wonder we're looking for fast food and fast weight loss options, we spend more time at work and less time in our homes and kitchens than our parents did.Sometimes you only have time to pack a leftover pizza slice and a slim-fast for lunch, irony be damned.