nebusoku no sei de asa kara zutuu ga site, syokuyoku mo amari nakatta.

It means because of lack of sleep or due to not getting enough sleep.

Grammar breakdown:

• 寝不足 = lack of sleep
• の = links the noun to what follows
• せい = cause, often with a negative nuance
• で = marks the reason/cause in the sentence

So 寝不足のせいで is literally something like by the cause of lack of sleep.

A key point: せい often implies that the cause led to an unwanted result. So this sounds natural here because the speaker got a headache and had little appetite.

Because 寝不足 is a noun, and せい is also functioning like a noun. In Japanese, when one noun modifies another noun, の is commonly used.

So:

• 寝不足 = lack of sleep
• 寝不足のせい = the cause being lack of sleep / the fault of lack of sleep

This is similar to patterns like:

• 雨のせいで = because of the rain
• 仕事のせいで = because of work

You can think of Aのせいで as a fixed pattern meaning because of A in a negative sense.

Yes, it is different.

せいで usually has a negative or blaming nuance. It often suggests that something caused an unfortunate result.

In this sentence, the speaker is saying the headache and lack of appetite happened because of sleep deprivation, and the tone implies this was a bad thing.

Compare:

• 寝不足のせいで、頭痛がした。
  Because of lack of sleep, I got a headache.
  → sounds negative, like sleep deprivation is to blame

• 寝不足だから、早く寝る。
  Because I’m sleep-deprived, I’ll go to bed early.
  → more neutral statement of reason

• 寝不足なので、今日は休みます。
  Since I’m sleep-deprived, I’ll take the day off today.
  → polite, neutral explanation

So せいで is especially common when the result is bad or inconvenient.

Because 頭痛がする is the standard expression for to have a headache.

In Japanese, many physical sensations or symptoms are expressed with 〜がする rather than 〜をする.

So:

• 頭痛がする = to have a headache
• 吐き気がする = to feel nauseous
• 音がする = to hear a sound / a sound occurs
• 匂いがする = to smell something / there is a smell

Here, 頭痛 is treated as the thing that is occurring or being felt, so が is used.

Because して is the て-form of する, and it connects this clause to the next one.

The sentence has two linked results:

1. 朝から頭痛がして = I had a headache from the morning
2. 食欲もあまりなかった = and I also didn’t have much appetite

Using the て-form here is like saying:

• I had a headache from the morning, and...
• I had a headache from the morning, so...

It keeps the sentence flowing into the next clause.

If you said 頭痛がした, that would sound more like the sentence ended there, unless you used another connector afterward.

朝から means from the morning or since morning.

Breakdown:

• 朝 = morning
• から = from, starting at

So 朝から頭痛がして means the headache had been there starting in the morning.

It does not necessarily mean all morning long in a strict sense, but it strongly suggests the symptom started in the morning and was present from then on.

Examples:

• 朝から雨が降っている。 = It has been raining since morning.
• 朝から忙しい。 = I’ve been busy since morning.

も means also, too, or as well.

The sentence first mentions one bad effect:

• 頭痛がして = I had a headache

Then it adds another:

• 食欲もあまりなかった = I also didn’t have much appetite

So も shows that lack of appetite is an additional symptom/result.

Without も, the sentence would still make sense, but も makes the relationship clearer:

• one problem: headache
• another problem too: poor appetite

Because あまり is commonly used with a negative form to mean not very much or not much.

So:

• あまりなかった = there wasn’t much / I didn’t have much

In this sentence:

• 食欲もあまりなかった = I also didn’t have much appetite

This is a very common pattern in Japanese:

• あまり食べない = don’t eat much
• あまり好きじゃない = don’t like it very much
• あまり元気がない = don’t have much energy

A very important learner point: あまり usually pairs with a negative expression in standard Japanese.

Both are possible. The difference is mainly style.

• なかった = plain past
• ありませんでした = polite past

This sentence is in plain style overall:

• 頭痛がして
• なかった

So 食欲もあまりなかった matches that casual/plain narrative style.

If you wanted to make it polite, you could say:

• 寝不足のせいで、朝から頭痛がして、食欲もあまりありませんでした。

That would be natural too.

Yes, 食欲があまりなかった is possible.

But in this sentence, も is taking the role that が might otherwise play.

Japanese particles often replace one another depending on what you want to emphasize. Here:

• 食欲があまりなかった = I didn’t have much appetite
• 食欲もあまりなかった = I also didn’t have much appetite

The speaker wants to add appetite loss as another symptom, so も is more natural than が.

Yes, most likely.

Japanese often leaves out the subject when it is clear from context. In English, we usually need I, but in Japanese it is often unnecessary.

So the sentence naturally implies something like:

• I had a headache since morning and I also didn’t have much appetite.

The full version with an explicit subject might be:

• 私は寝不足のせいで、朝から頭痛がして、食欲もあまりなかった。

But in natural Japanese, 私は is often omitted if the speaker is clearly talking about themselves.

The comma helps separate the two connected parts of the sentence and makes it easier to read.

Japanese punctuation is often more flexible than English punctuation, but here the comma marks a pause after the first clause:

• 朝から頭痛がして、
• 食欲もあまりなかった。

It shows that the first clause leads into the second. Even without the comma, the grammar would still work, but the comma makes the sentence smoother and clearer.

Yes. Here are a few natural alternatives, each with a slightly different nuance:

• 寝不足で、朝から頭痛がして、食欲もあまりなかった。
  More neutral than せいで; simply states lack of sleep as the reason.

• 寝不足のせいか、朝から頭痛がして、食欲もあまりなかった。
  Maybe because of lack of sleep...
  This sounds a little less certain.

• 寝不足だったので、朝から頭痛がして、食欲もあまりなかった。
  More neutral explanatory tone.

The original sentence is especially natural when the speaker wants to stress that lack of sleep caused these unpleasant symptoms.