It’s not just “harder”, it requires skills and knowledge, which most people don’t actually have.
The point is that “exercise” isn’t helpful advice to lose weight. First, it’s not terribly effective at it over short durations, and people need to know that what they’re doing is working. Second, if somebody isn’t already exercising, they’re going to hurt themselves, have a six week recovery time, try again, hurt themselves, and give up on losing weight. Third, you’re communicating something different than what you think you are; “Go for a walk every day” is good advice, by comparison to “exercise”. The temptation is to object that that is exactly exercising—but it isn’t what people think when you tell them to exercise.
I’ve been both. My natural tendency, absent constant pressure, is to settle 40-50 pounds over my ideal weight—and it’s relatively easy for me to lose weight now, but mostly because I know it’s possible. The first time I lost weight, willpower had nothing to do with it—I had a minimum-wage job that kept me constantly active, and I didn’t feel like I could afford to waste money on anything but the minimum sustenance of food. So I was dieting and exercising against my preferences. Since then, I’ve been able to lose weight—because I knew it was possible. Without the prior experience of having lost weight, it feels like an impossible achievement.
The information I have seen suggests a pound of fat requires 2-3 kilocalories per day to maintain itself, which implies a range of 30-47.5 pounds from a 95 kilocalorie deviation, which would be 13-20 kilograms.
I have no idea how accurate that is, but it doesn’t matter too much, as the underlying point remains the same: People’s expectations of food consumption necessary to be overweight are entirely inaccurate. Fat people think thin people must be eating almost nothing at all, thin people think fat people must be eating three hamburgers per meal, where the actual difference is quite small, relative to our out-of-whack expectations.