How do I politely decline a lunch invitation from a friend's family?

Question

I frequently go over to my friend's house on the weekends to work on projects. We usually meet up in the morning then work until lunch before we go our separate ways. My friend still lives with his parents who, while are nice, tend to be overly courteous.

Because of this, often when I'm about to leave, they insist I stay for lunch. While I do find the food to be good, there are often times I do not wish to stay for lunch. On one such occasion, I had made lunch plans with my significant other, and upon telling them this, they still insisted I eat lunch at their house. I was still going to be at their house for another hour to complete some work, so I wasn't sure how to decline this invitation. I ended up eating lunch there, then had to skip eating at my lunch date.

There was another occasion when I had a large breakfast, and by the time I arrived to my friend's house, much of his family has not eaten anything for the day. They invited me for breakfast and I told them I had a large breakfast and was not hungry. Despite this, they still insisted, and I had to force myself to eat a second breakfast.

There are times when I do not have lunch plans and very much enjoy eating there, but I also do not want to be expected to eat there every time I'm invited to. How can I decline having to eat there without coming as rude or making it sound like I'm not interested in an invitation in the future?

Edit: The location is in the US. The family itself come from a Pakistani culture.

Answer 1

In general, I find following phrases useful. You just have to tell the truth, more or less:

Oh, thanks for the invitation, but I have lunch with my SO in an hour. Should probably save some space for it. (Alternatively: I will be late for lunch with my SO, gotta go, sorry)

I just had a big breakfast, but maybe I can ask for a quick cup of coffee before start working?

Work-related excuses should work too (since you probably want to start working right away)

We have a lot of work to cover, it's better if I start right away. But can I ask for glass of water/juice/cup of coffee/tea?

Finally, you have an ally (hopefully), that is your friend. Tell them that these invitations sometimes are uncomfortable but still welcome:

Hey, Jane/Joe Doe, I really appreciate invitation, but I'd like to work / leave. Would it be OK if I go, it's really hard to resist your family.

More general "solution" From your post it seems that these people really like you, so maybe you want to schedule (again, talking to your friend) staying over for lunch, rather than let them decide. Take the initiative. For example, you can tell friend:

I really like your family, could I join you folks for lunch next week, I'll bring some stuff from my family cookbook?

This way there will be no doubt that you like these people back, but some days are better than others for you.