Tā xiào zhe pāi le pāi dùzi shàng de "jiùshēngquān".
He laughed and patted his 'spare tire' (belly fat).
Tips
memory
救 (save) + 生 (life) + 圈 (ring) — literally 'save-life ring'. The transparent compounding makes it easy: a ring that saves lives.
usage
The slang sense — using 救生圈 for the roll of fat around someone's waist — is gentle and self-deprecating, parallel to English 'spare tire'. Often written in quotes when used this way.