fatten up

Verb

fatten up (third-person singular simple present fattens up, present participle fattened up, simple past and past participle fattening up)

1. (transitive) To cause to gain weight by means of feeding.
   • My cat looks underweight, so I'll fatten him up with higher-calorie cat food.
   • I visited my mother for a month, and she managed to fatten me up 20 pounds.
2. (intransitive) To become fat or fatter by gaining weight.
   • ‘And isn’t Declan looking very thin?’ Madge said. ‘He’ll never get a wife if he doesn’t fatten up a bit.’1999, Colm Tóibín, chapter 8, in The Blackwater Lightship, New York: Scribner, page 246
3. (figuratively, transitive) To make bigger; to expand.
   • We must not fatten up our payroll with people performing nonessential activities.1954, United States. Congress. House. Committee on Appropriations, Department of the Army Appropriations for 1955: Hearings, page 161