It follows your key strokes and looks at key words like lose weight weight loss exercise and uses these key words to target ads at you.
Years ago I talked about losing weight in private messenger. And loads of fitness ads came up. Also if you’re on Apple as I am, when you google lose weight Facebook might be following at that too. This may also happen if you go on Bandboozled. There is nothing wrong with that group, but when their software sees the name weight loss and lose weight frequently on that group it will try to sell you weight loss stuff.
Remember Bandboozled will only advertise its own products and services.