Perhaps a dumb question? Please be kind.

So I am having a really hard time understanding this concept. I hope this is the right sub. Low carb dieters often explain that when you eat low carbs your body switches to burning fat as fuel because there aren’t enough carbs for energy. However, if you eat in a calorie deficit (at least from my understanding?) your body will lose fat as well. So my question is, it really doesn’t matter what you are eating as long as you burn more calories than you take in right? So if someone went low carb and way exceeded their calorie needs they would gain fat not lose it right?