Specifically, 51 percent of parents did not understand that a child in the 10th percentile for height (meaning they are shorter than most of their peers) and 90th percentile for weight (meaning they weigh more than most of their peers) was overweight.

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"If you weigh 300 pounds and eat healthy, the weight will still counter any beneficial foods you are eating, " Dr. Cannon says.

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He said one way to minimise the risk of the condition going undiagnosed would be to weigh patients every time they sought medical help, so that any signs of weight loss would be recorded at an early stage.

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Someone who seems to weigh a lot on the scale may have a healthy BMI and not need to lose weight.

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Expected to weigh roughly 1.2 million pounds, the combination would roughly match the maximum takeoff weight of the largest, fully loaded Airbus A380 superjumbo plane, but the wings would be more than 120 feet longer than those of the Airbus A380.

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"The absolute best thing about all the weight that I've lost is just waking up every day and realizing that I don't weigh 577 pounds anymore, " he said with a laugh.

CNN: Man refuses surgery, drops 270 pounds

While the surgeries are successful at helping people lose weight and reduce their risk for hypertension, diabetes and other chronic illnesses -- patients have to carefully weigh the benefits of the procedure with the serious risks, side effects and even death in some cases.

CNN: Surgery helps woman drop 135 pounds, 10 dress sizes