go on a diet （为了减肥）而规定饮食；节食
例句：
Mary went on a diet and lost four pounds. 玛丽因为节食瘦了四磅。 I'm gaining weight.I must go on a diet. 我的体重在增长，我必须要节食。 The doctor said I am a little overweight.So I shouldgo on a diet. 医生说我有点超重，所以我需要节食。
背景音乐： Glee Cast-Saving all my love for you