fatten up

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.
   • 1999, Colm Tóibín, chapter 8, in The Blackwater Lightship‎^[1], New York: Scribner, page 246:

     ‘And isn’t Declan looking very thin?’ Madge said. ‘He’ll never get a wife if he doesn’t fatten up a bit.’

3. (transitive, figurative) To make bigger; to expand.
   • 1954, United States. Congress. House. Committee on Appropriations, Department of the Army Appropriations for 1955: Hearings, page 161:

     We must not fatten up our payroll with people performing nonessential activities.