Like most fat people, I'm not fat because I take in more calories than I burn. I'm fat because I take in the same amount of calories that I burn. A 170-pound woman with a stable weight eats only about one slice of bread more than a 120-pound woman of the same activity level with a stable weight. I'm not 170 pounds because I overeat, but because I eat, literally, exactly as much as I need to.
Whether I should start eating less than I need is a complicated question and one I go back and forth on. But it's not a matter of merely "stopping overeating."
The decision to diet is not to "eat healthy." It's the nontrivial question of whether to eat deliberately unhealthy in hopes of a long-term tradeoff.
(The terminology question of how to say I'm not the same height-weight ratio as the ladies in the magazines always drives me nuts. "Overweight" implies that there's some Platonic ideal Holly whom I'm fatter than. Things like "chubby" are evasive and imply I'm ashamed of myself. [And I'm really not "curvy." I'm built less like the Venus of Willendorf, more like a miniature linebacker.] So I go with "fat," even though I worry that it makes me sound fat-fat, headless ladies in news reports fat, when I'm not even a plus size. But getting too pointed about "hey, I'm not even a plus size!" is kinda undercutting to people who are, and aren't somehow worse than me. So, yeah, "fat.")