One time, I was walking along in Tokyo, and I saw a sign advertising "The Pelvis Diet."

No, seriously. Here's an image:

簡単！骨盤ダイエット
kantan! kotsuban daietto.
It's easy! The Pelvis Diet.
(Literally: "Easy! Pelvis + Diet.")

My first thought was, No, man, you're just messing up the kanji or something. There's no such thing as a Pelvis Diet.

But then I looked up the words, again and again, and there was no mistake:

骨盤
kotsuban
pelvis

ダイエット
daietto
diet

I soon learned that the problem was this word ダイエット (daietto).

In English, the word "diet" strictly refers to the food we eat, yeah?

But in Japanese, ダイエット (daietto) refers to "food and exercise."

Or in the case of the 骨盤ダイエット (kotsuban daietto), apparently it's the process of realigning your pelvic bone with weirdo stretches:

産後骨盤ダイエット
sango kotsuban daietto
Post-Pregnancy Pelvis Diet

女性の「やせない」「調子が悪い」は
骨盤の歪みが原因だった！
josei no "yasenai" "choushi ga warui" wa
kotsuban no yugami ga genin datta!
The reason that some females "just can't lose weight"
or "just don't feel right:" pelvic misalignment!
(Literally: "females + の + 'not get thin' + 'condition is bad' + は
+ pelvis + の + deformation + が + cause + was."
(Sorry for the super long example.)

There are quite a few loan words like ダイエット (daietto) with slightly different meaning, which are referred to as:

和製英語
wasei eigo
Literally: "Made-in-Japan + English."

I talked about this with the Japanese words for "interview" recently in an article on my site.

Anyways, finding 和製英語 (wasei eigo) is one of the most fun parts of learning Japanese. So look forward to one day coming across your own version of "The Pelvis Diet."

Bonus Phrases:

骨盤がゆがんでるみたい。
こつばん　が　ゆがんでる　みたい。
I feel like my hips are getting bent out of place.
Literally: pelvis + ga + is warped + looks like
Note: Ah! I can't translate this! "It looks like my pelvis is warped," would be strange in English, yeah? For example, a person could use this Japanese sentence when they've been standing waiting in line for a long time, and their pelvic area (i.e. hips?) feel strained and out of shape.

今ダイエット中。
いま　ダイエット　ちゅう。
I'm on a diet.
Literally: now + diet + inside

ノートパソコンって和製英語なんだって。
ノートパソコン　って　わせいえいご　なんだって。
Apparently "Note PC" is Japanese English.
Literally: Note PC + って + Made-in-Japan + English. + なん + is + って