# fatten up

CEFR B1 · Phrasal verb

Source: https://englishreference.com/word/fatten-up
Updated: 2026-04-24

## Definition

to make a person or animal gain weight, often by giving them a lot of food.

For teachers: to increase the body mass or fat content of a person or animal through deliberate overfeeding; often used in agricultural or caregiving contexts.

## Examples

- The farmer is trying to fatten up the cows for winter.
- My grandmother always tries to fatten me up with her homemade pies whenever I visit.
- The livestock were moved to the lower pastures to fatten up on the lush spring grass before being sent to market.

## Pitfalls

- Not "He wants to fat up the bird." but "He wants to fatten up the bird." — the verb is 'fatten' (to make fat), not the adjective 'fat'.

## Usage notes

- can be used for animals (literal) or people (often slightly humorous or affectionate).
- Teaching tip: this is a transitive phrasal verb that can be separated by the object; it follows the pattern of 'adjective + en' verbs like 'shorten' or 'widen' combined with the particle 'up' to show completion.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.