I'm having a light/heavy lunch.

[tulipflower]

To express eating habits, Jack. C. Richards & David Bohkle in their book 'Speak Now 1', p. 67 have used this structure: 'I'm having a light/ heavy lunch.' I have learned this structure can express either 'present progressive tense' or 'a planned future action (be going to).' I wonder what 'I'm having' means in the aforementioned sentence.

 

[tulipflower]

Unfortunately, there isn't sufficient context in the book.

 

[Charlie Bernstein]

Then there you are.

You're either having that lunch right now or tomorrow or on your hundredth birthday.

We can only be sure that you're not having it yesteday — unless you're a time traveler.