The story behind this one: As my mom got older she put on quite a bit of weight even though she ate very little. (The doctor put her on a reducing diet and she started GAINING weight because she normally didn't eat that much.)
She worked at a school and she said one of the problems was that her CO-WORKERS were all quite overweight, so she found it hard to think of herself as overweight. I replied, "Oh ... so they're on a "fatten-up their friends" diet."