Will 90 percent of Americans be fat by 2030?

It was one of those numbers, like $10 a gallon gas or $20 six-packs, that seems designed to shock and appall and cause the head to shake in disbelief.Could it really be that almost 9 out of 10 American adults will be overweight or obese in less than 25 years? That's what a new study, based on national surveys done over the past three decades, warns could happen if the nation's weight-gain trends since the 1970s continue until 2030.The research was carried out by scientists at John Hopkins University and the federal Agency for Healthcare Research and Quality and published online in the journal Obesity.Currently, about two-thirds of American adults are considered either overweight or obese, as are about a third of school-age children.Of course, the dire predictions are based on assumptions that people will continue behaving -- and putting on the pounds -- just as they have for the past 30 years, driving everywhere, eating big mounds of unhealthful fast food, getting less and less exercise.To be sure, carrying many extra pounds and living a sedentary lifestyle is not good for anyone. It increases the risk for many health problems from diabetes to stroke and heart disease to arthritis and some types of cancer. Many experts think there are already so many super-sized Americans that a century-long trend of greater life expectancy has slowed and may soon reverse.But there have been some modestly encouraging signs that Americans, if not shrinking, are at least not growing heavier. Government reports last fall suggested adult obesity rates were static, and a May report showed childhood obesity rates were also steady, maybe even a slight decline in some places.Some experts took the report on kids, in particular, as a positive sign that a broad public health focus on reducing childhood obesity may be starting to pay off. Others warn that most overweight kids will still become even more overweight and obese adults, with long-term health consequences.Medical science certainly has been aggressive in finding solutions, ranging from stomach-shrinking surgery in several forms to new food formulas to research into various genes and hormones that spur us to eat or not eat.One sure bet is that not all of us take the same biological path to obesity and it will take some pretty personalized medicine to get us slim again.You only have to consider "those people" -- you know, the ones with the fast metabolism who seem to eat what they like and never gain weight -- to appreciate that genes are a factor in jeans size.We also know that the obesity battle is full of moving targets. Don't forget that shifting food pyramid, or that the government tumbled millions into the overweight category a decade ago by shifting the BMI threshold from 27 to 25.Likewise with the recommended daily level of activity, which has variously roller-coastered in recent years from an hour or more a day of exercise down to as little as 30 minutes a day.Now, in the most recent report in the Archives of Internal Medicine, the suggested moderate workout is back up to 55 minutes a day at least five days a week for overweight and obese women (and probably men, too) to sustain a weight loss of 10 percent for at least two years.Recent government surveys show that more than 60 percent of adults report devoting at least some of their leisure time to physical activity each week, with about 31 percent getting regular workouts. That's not 100 percent, but it's a few steps in the right direction away from 90 percent being overweight, too.On the Net:http://www.nature.com/oby/journal/vaop/ncurrent/abs/oby2008351a.htmlarchinte.ama-assn.org/(Distributed by Scripps Howard News Service, http://www.scrippsnews.com)