Whether you develop cancer or not is not determined by your eating habit(s).
Should I use habit or habits?
" You likely have several eating habits. For breakfast, you might always have cereal. For lunch, you might usually have a sandwich.
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I'd go with "habits." You likely have several eating habits. For breakfast, you might always have cereal. For lunch, you might usually have a sandwich. You might drink coffee throughout the day. When you dine out, you usually have a medium rare steak. And so on.
A quote from Merriam-Webster Online Dictionary:
teacherJapaneating habit(s)
Another possibility is to replace this with diet. You can choose.