I disagree with losing weight being easy. It's easy in "theory," and if you only have 10-20lbs to lose it's pretty straightforward.

Enter human psychology, "real life" (stress, kids, a job, social life, etc), and the fact that maybe you have 80lbs to lose. That, at a healthy pace, can take a full year to lose. Or 80 weeks (nearly a year and a half) if you go one pound a week. That's a long time to stick to a "diet."

That's why most people need to focus on a lifestyle change. A Diet implies short term in most people's mind, and that's why most people revert. Yay, I lost 80lbs, now let's start eating donuts for breakfast, McDonalds for lunch, and pizza for dinner again. It's trivial to gain weight. It's harder, much harder, to lose it.

FWIW, I'm a weightlifter. I've been as much as 50lbs overweight, lost that weight and kept it off for many years. I've also gone through the bodybuilding "bulking/cutting" cycle that was popular for so long (and maybe still is, I don't do that anymore), so I'm quite familiar with gaining 20-30lbs and cutting down again in cycles. So I know weightloss is straightforward and simple, but I totally disagree that it's easy.

I have no idea why people are voting you down. It must be out of pure utter ignorance with no practical experience in trying to do this. As someone who weight lifts naturally what you said is factually correct viz. (a) it is as easy as counting calories and eating at a deficit. (b) it's difficult to eat at a deficit and keep muscle mass because you're essentially low on fuel and your body has to burn something for energy, trying to stay out of a catabolic state requires diligence.