Two e-mails from mothers, similar in content but separated by about 15 years, clearly suggest that a once understandable increase could now be an incomprehensible event. Both mothers were worried about their son's weight.

The e-mail from 15 years ago asked for ways to get a pudgy, video-game-playing son more active and to eat less junk. Composing a response was easy.

Composing the more recent response, however, was not.

That mother wanted to know how could her son could still be soft around the waist and carrying a few too many pounds when he was working out between 12 and 15 hours a week and eating many healthy foods.

No single e-mail will contain the answers to that one. A detailed analysis of the foods consumed and the type and intensity of the workouts, plus a few discussions with the boy, the food consumer, and the mom, the food producer, will be required. We're in the middle of that process as I write this.

But the answer to one boy's specific problem is not the crux of this column. The fact that the mother even needed to ask the question is.

It wasn't that long ago that exercising two hours a day regardless of what you ate especially if you were a teen would've kept you from a mushy middle. Not so anymore.

There are a whole host of factors making it tougher for teens to be fit than ever before. Today's column will explore two of those.

The first is the extremely easy access teens have to what many call empty calories calorically dense energy sources that digest quickly, provide little in the way of nutrition, and make you more likely to eat again.

An article published last fall in the Journal of the American Dietetic Association reported that over half the calories consumed by American kids fall into the empty cals category. The researchers used a nationally representative survey, the National Health and Nutrition Examination Survey (NIHANES), and found that the two main culprits are high-calorie drinks and junk food.

In fact, high-calorie drinks which means they are sugar sweetened accounted for 10 percent of that total caloric consumption.

Take a moment to appreciate that statistic. It means the typical athletic, high school male in the middle of a demanding sports season who needs 3,500 cals to maintain his weight is getting 350 calories a day from soda, sports drinks, and fruit drinks.

NIHANES counts the cals from fruit juices separately though your body is affected by all sugary beverages similarly so if the aforementioned male begins his day with a tall glass of apple, cranberry, or orange juice, he's consuming about 550 sugary liquid cals per day.

Those calories not only provide little nutrition though fruit juices provide some but they also are not recognized by the body as energy, which generally leads to overeating.

Combine that with the overeating triggered by the overload of blood sugar that occurs from the consumption of the solid empty calories foods like pizza, French fries, and assorted sweets like grain desserts and it's easy to understand why kids are heavier than ever before.

But a second factor exacerbates this weight gain: the relative lack of sleep of children and teens. It actually programs the body to expend fewer calories and crave more.

Partial proof of this is in research compiled by Dr. Carol Maher, Tims Olds and Lisa Matricciani and published in the journal Sleep this fall. These three found that Australian teens who went to bed late were 1.5 times more likely to be obese than those who adhered to an early bedtime.

Considering that many experts believe a teen needs a minimum of nine hours of sleep a night and preteens can need up to 11, it's safe to say that the majority of American kids are sleep deprived.

This lack of sleep, however, does more than make kids more likely to gain weight. It also increases their risk of type two diabetes, impairs their immune systems, increases their eventual risk of heart disease, and leads to irritability.

The researchers also found a correlation between a late bedtime and a lack of exercise, which further increases the likelihood that the first factor, the eating of empty calories, is going to lead to weight gain.