1
a dieter
dieter 是可数名词，单数前常用 a/an。
She is a dieter and avoids sugary drinks.
她是个节食者，避免含糖饮料。
节食者
先理解核心含义，再看它在真实句子里的用法。
节食者
a person who diets
She is a dieter and avoids sugary drinks.
她是个节食者，避免含糖饮料。
节食者。
A person who diets, usually in an effort to lose weight.
The dieter carefully counted calories at every meal.
这位节食者每餐都仔细计算卡路里。
Many dieters find it hard to resist snacks at night.
许多节食者发现晚上很难抵制零食。
A successful dieter usually keeps a food journal.
成功的节食者通常会写饮食日记。
dieter 是可数名词，单数前常用 a/an。
She is a dieter and avoids sugary drinks.
她是个节食者，避免含糖饮料。
定语从句修饰 dieters 时，关系代词用 who。
The diet plan is designed for dieters who want to lose weight gradually.
这个饮食计划是为想要逐渐减肥的节食者设计的。
Not this
I dieter to lose weight.
Use this
I diet to lose weight.
dieter 是名词，指“节食者”；句子需要谓语动词，表示“节食”动作应用动词 diet，所以改为 I diet。
Not this
She is a dieter woman.
Use this
She is a dieting woman.
dieter 是名词，不能直接修饰 woman；修饰人表示“正在节食的”应用现在分词 dieting，或说 a woman on a diet。
Not this
I am on a dieter.
Use this
I am on a diet.
固定搭配是 be on a diet（在节食），diet 作名词指“日常饮食/节食计划”；dieter 指人，不用于 on a ... 结构。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
节食成功的人
A successful dieter usually plans meals in advance.
节食成功的人通常会提前规划好三餐。
急速节食者
Crash dieters risk losing muscle rather than fat.
急速节食者减掉的可能是肌肉而不是脂肪。
终身节食者
She is a lifelong dieter who has tried every diet book.
她是个终身节食者，读过所有减肥的书。
习惯性节食者
Many serial dieters gain the weight back quickly.
许多习惯性节食者很快就会反弹。
体重反复的节食者
Yo-yo dieters often struggle after each diet ends.
体重反复的节食者通常在每次节食结束后都很挣扎。
Use dieter naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
dieter = diet（节食）+ -er（人），节食者管住嘴，面对美食不动心。
语域：neutral 常见场景：health and fitness、everyday conversation 该词为中性常用词，通常见于日常对话或健康、减肥话题，在一般书面语中也可使用，无明显正式或俚语色彩。
指为了减肥或健康而节制饮食的人，常用于谈论减肥计划的语境。
Dictionary facts from ECDICT, WIKTIONARY.