"Three meals a day" 的英语表达方式是 "three square meals a day"。
其中 "square" 意为 "正餐"，引申为 "足够的食物"。 "Three square meals a day" 意思就是每天有三餐足量的食物。
这种表达方式源自19世纪，当时军队会提供给士兵三餐固定的食物，而这些食物就是指“square meals”。
例句：
I try to eat three square meals a day to keep my energy levels up.
我尽量每天吃三餐来保持我的精力水平。
He never skips a square meal.
他从不错过一餐正餐。
To make sure I'm getting enough nutrition, I try to eat three square meals a day.
为了确保我摄取足够的营养，我尽量每天吃三餐。