Unfortunately...

One member of the SHK team noticed a strange construction in a piece of text written by our teacher. The sentence actually has more interesting things in it. It runs:

In kanji: 美味しい 食事を　食べ過ぎて　少し太って　しまいました。
In hiragana: おいしい　しょくじを　たべすぎて　すこし　ふとって　しまいました。
The beginning is easy: delicious meal [OBJ]. The next word, たべすぎて, comes from たべすぎる, which means 'to overeat'. This may sound and look like some weird derivation from たべます, to eat, and in fact, the kanji 食 at the beginning is the same as for 'to eat' (and also the same as for 食事, meal). But the word たべすぎる is separately listed in the dictionary, and, say, the made-up のみすぎる ('to drink too much'), is not. So it looks like a separate word.
So it's "we ate too much of the delicious food and..."
少し (すこし) is known as 'a little'.
Then two verbs: 太って (ふとって), the -TE form of 太る (ふとる),'to gain weight', and しまいました, the polite past tense of しまう, listed as 'to finish', 'to put away'. This one is a puzzler, but internet to the rescue, pointing out that ~て　しまいます (or ~て　しまいました if talking about the past) is used to express regret.
So the whole sentence reads: "We ate too much of the delicious food and regrettably gained a little weight."