Others don't exercise because they've adopted a "Why bother?" attitude, says Gaesser. "People often start an exercise program to lose weight. When the weight doesn't roll off, and it usually doesn't, they give up because they feel they've failed. They only failed because they focused on the wrong outcome. The goal should be that they exercise for 30 minutes or more most days of every week. That's success."
However, neither Blair nor Gaesser endorses obesity. "When people hear me say fat people can be fit, they think I'm saying it's OK to be fat, or that it's better to be fat," says Gaesser, himself a gaunt 6 feet 4 and 185 pounds. "I never said obesity isn't a health problem. I am saying that the health risks of obesity are exaggerated."
There's also a point, experts agree, at which a person gets so heavy that he or she couldn't possibly be fit. For example, no one in the Cooper study had a BMI of more than 35.
But for those genetically destined to have corpulent bodies, the movement to accept fit at any size is a relief. "For years I prayed every day to be thin," says Rubinsky, whose parents put her on her first diet when she was 6 so she wouldn't end up looking like her mother. "I thought thin equaled success, love and happiness. Now I'm the happiest I've ever been: I have a dream job getting paid to do what I love to do most -- dance. I help others, have tons of energy, feel great, am dating a great guy -- and I'm not thin. Like I tell the people in my class, being thin isn't the answer, being healthy is."