Americans are fatter than ever and it's seriously harming our health. More than 72 million adults are obese, and that figure is expected to soar to 103 million by 2018. The problem is so bad that it could even cause life expectancy to start to decline, according to some demographers.

The good news is that basic research is helping scientists understand why we eat too much and how we can best lose weight. One major finding from earlier this year is that human adults have stores of calorie-burning brown fat, long thought to exist only in newborns and certain animals. But it turns out to also be present in small quantities in adults.