I don’t think it’s very nice to mock someone for gaining weight because you disagree with them saying it’s easy to lose weight.
I gained a lot of weight because I was depressed and suicidal. Cooking is one thing I enjoy, and eating is something I enjoy even more. Because of my mental health difficulties I was stuffing my face, and I gained what I consider to be an unacceptable amount of weight.
I was able to lose all of that rather quickly by just not eating carbohydrates and sugars. There are many names for this, keto, Atkins, low-carb.