Having eaten more, he got bulky. Here ‘having’ works as a/an

Present participle এবং Past Participle এর সমন্বয়ে Perfect Participle গঠন করা হয় ।
Structure : Having + past participle.

• তাই এখানে ‘having’ হলো Participle.

Example of participle:
- Having completed the work, I went home.
- Having gone late, he missed the train.

Source: Advanced Learner's Grammar & Composition by Chowdhury & Hossain.