As someone who is loosing weight it’s basically calories in and calories out without eating over your daily calory budget

loseit is a good app and will calculate your calory budget for you and can track the foods you eat and add them up

I feel sorry for you americans though that don’t have the per 100g on your nutritional labels though because serving sizes can be deceptive

Wait… They don’t have that level of detail on the labels?? That’s ridiculous? Serving size is arbitrary nonsense.

They do, just not in the units you’re familiar with. They do calories per serving, and very commonly servings per package (in cases where people may be likely to eat the entire thing.) When listing serving sizes, where appropriate the serving sizes is described (how many pieces) and a weight in grams is listed.

Here’s an example (haven’t gotten around to posting images - sorry for the link.)

images.app.goo.gl/km9a4TUX8cbC32zA7