Downsize Fitness founder Francis Wisniewski is seen at one of his gyms in Chicago. The gym chain he started caters exclusively to people who want to lose at least 50 pounds.  | Teresa Crawford ~ The Associated Press

A trainer runs a morning exercise class at Downsize Fitness Thursday, Jan. 3, 2013, in Addison, Texas. Downsize Fitness is a selective gym where the rule is that new members must tip the scales. New members are weighed and have their body mass index measured. | LM Otero~The Associated Press

A trainer runs a morning exercise class at Downsize Fitness Thursday, Jan. 3, 2013, in Addison, Texas. Downsize Fitness is a selective gym where the rule is that new members must tip the scales. New members are weighed and have their body mass index measured. LM Otero ~ The Associated Press

Personal trainer Krisaane Hale, right, weights Ellen Hays for a body mass index reading before working out in a morning exercise class at the Downsize Fitness gym in Addison, Texas, Thursday, Jan. 3, 2013. LM Otero ~ The Associated Press

Personal trainer Krisaane Hale, right, weights Ellen Hays for a body mass index reading before working out in a morning exercise class at the Downsize Fitness gym in Addison, Texas, Thursday, Jan. 3, 2013. Downsize Fitness is a selective gym where the rule is that new members must tip the scales. New members are weighed and have their body mass index measured. (AP Photo/LM Otero)

Gym members use as treadmill to warm up for a morning exercise class at Downsize Fitness Thursday, Jan. 3, 2013, in Addison, Texas. LM Otero ~ The Associated Press

Gym members use as treadmill to warm up for a morning exercise class at Downsize Fitness Thursday, Jan. 3, 2013, in Addison, Texas. Downsize Fitness is a selective gym where the rule is that new members must tip the scales. New members are weighed and have their body mass index measured. (AP Photo/LM Otero)

A gym member arrives for a morning exercise class at Downsize Fitness Thursday, Jan. 3, 2013, in Addison, Texas. LM Otero ~ The Associated Press

A gym member arrives for a morning exercise class at Downsize Fitness Thursday, Jan. 3, 2013, in Addison, Texas. Downsize Fitness is a selective gym where the rule is that new members must tip the scales. New members are weighed and have their body mass index measured. (AP Photo/LM Otero)

Ellen Hays works out during a morning exercise class at a gym in Addison, Texas, Thursday, Jan. 3, 2013. LM Otero ~ The Associated Press

Ellen Hays works out during a morning exercise class at a gym in Addison, Texas, Thursday, Jan. 3, 2013. Downsize Fitness is a selective gym where the rule is that new members must tip the scales. New members are weighed and have their body mass index measured. (AP Photo/LM Otero)

Personal trainer Krisaane Hale, bottom, measures Ellen Hays for body mass index reading before working out in a morning exercise class at the Downsize Fitness gym in Addison, Texas, Thursday, Jan. 3, 2013. LM Otero ~ The Associated Press

Personal trainer Krisaane Hale, bottom, measures Ellen Hays for body mass index reading before working out in a morning exercise class at the Downsize Fitness gym in Addison, Texas, Thursday, Jan. 3, 2013. | LM Otero ~ The Associated Press