If you've ever watched pigs eat, you will certainly have noticed that they have no control over their eating habits. The very sight of food makes them want to fill their bellies¹, and they don't know when to stop! From that, anyone who eats a lot or can't stop eating makes a pig of himself/herself. This is generally used humourously (幽默地).

　　"I made a pig of myself at Jane's party. I think I sampled everything on the buffet² table."

　　狼吞虎咽

　　如果你曾经看过猪吃东西的话，你一定会发现它们毫无吃相可言。只要一看见食物，它们就想把胃塞满，根本不知道什么时候该停止。由此，某人吃得很多或者是吃得停不下来就可以说是 makes a pig of himself / herself。这个词组一般可以幽默地应用，“我在简的派对上狼吞虎咽，把自助餐桌上的食物尝遍了。”