It's one of those quotations that's so dead-on no one disputes it, like Ralph Waldo Emerson's observation, "Knowledge is the antidote to fear."

Almost 400 years ago, the English philosopher Francis Bacon wrote, "Knowledge is power." Since then, there's really been little reason to question him.Until the obesity epidemic.In the last 20 years, the number of overweight children and adult Americans has nearly tripled, yet during that same span our knowledge about nutrition, diabetes, and other weight-related subjects has probably increased tenfold.With all that knowledge, why's the overweight rate still so high? Is Bacon's observation bogus?No, but now there are other forces in society powerful enough to negate the newfound weight-related knowledge, namely technology. Did you know, for instance, that the typical American now burns 800 fewer calories daily than 33 years ago?That's because in 1978 most kids played outside all day during summer vacation. The only reason to stop playing kickball, wiffleball, King of the Hill, or tag was darkness or it was your night to take a tubby.Back then, most adults had far more physical jobs and had to be far more physical around the house. Lawn mowers were pushed, garage doors were lifted, and bathroom tiles were scrubbed.Now we have riding mowers, automatic garage door openers, a daily spray to clean the shower, and equally as significant for both children and adults new forms of entertainment.How many calories do you expend watching HDTV, surfing the Internet, or using the apps on your cell phone? Not any more than when you sleep and herein lies a great irony.For as sleep keeps getting shortchanged by our use of these new forms of entertainment, that tenfold increase in weight-related knowledge is telling us that sleep shouldn't be shortchanged, that the proper amount is paramount for effective weight-loss.Could a lack of sleep be the detail derailing your repeated attempts to lose weight?An article published in the Annals of Internal Medicine last October found a major difference between sleeping 8.5 hours a night or 5.5 hours a night while on a diet. The difference, interestingly enough, had nothing to do with the total amount of weight lost.At the conclusion of a two-week period where 10 overweight adults were fed low-calorie diets and lived at a sleep research center to keep their sleep at a constant 8.5 hours a night, their weight loss averaged 7 pounds, 3.5 pounds of fat and unfortunately 3.5 pounds of muscle mass.Because of this 50/50 split, we would generally say that the reduction in calories was too severe. A good goal for overall weight loss is for 75 percent of it to be body fat. If the percentage is lower than that, the odds increase that the weight loss will not be permanent.That's because muscle burns calories but fat doesn't. So any decrease in muscle mass reduces the daily need for calories.A 3.5 pound loss of muscle mass, for instance, reduces the daily need for calories by about 175. So if the dieters in this study return to eating the way they did before the diet, they regain the lost weight in 140 days.And one year after the diet ended, they are more than 11 pounds heavier than when the diet began.But the real news happened later.The same subjects returned, followed the same diet, but slept only 5.5 hours. The weight loss again averaged 7 pounds.But the composition of the weight lost was dramatically different: an average of 1.75 pounds of fat and 5.25 pounds of muscle mass.This time, the dieters' loss of muscle mass decreased their average need for calories by about 260 per day, 85 fewer than the 7-pound weight loss achieved on 8.5 hours of sleep.That difference of 85 calories per day is more than enough to derail the long-term success of a diet. If dieters who achieved a 7-pound weight loss by sleeping 5.5 hours a night want to maintain that weight loss for a year, they have to eat 31,025 fewer calories than dieters who lost the same amount of body weight while sleeping 8.5 hours a night.If the dieters who achieved the 7-pound weight loss on 5.5 hours of sleep a night return to eating the way they did before the diet, they regain the lost weight in 94 days. And one year after the diet ended, they are a bit more than 20 pounds heavier than when the diet began.Examples like these make it easy to see why weight loss done the wrong way is worse than no weight loss at all.Another study found another weight-related problem with not getting enough sleep: night owls tend to eat more total calories. A study done by Northwestern University found that staying up late even if you slept in! caused subjects to eat an average of 248 more calories.If not balanced by additional exercise, those 248 calls per day could lead to a weight gain of more than 25 pounds per year.Moreover, when compared to "normal" sleepers the night owls consumed twice as much fast food, half the amount of fruits and vegetables, and drank more full-calorie sodas.