I'm heavier than I'd like to be. Since I started keeping track in 2007, I'm up about 10 pounds. I know what the likely cause is -- beer, bread, chips, pizza and too much of it. When I cut down on these things, my weight drops. Simple as that.
There a lot of good documentaries now on diet on Netflix and Amazon Prime. The big takeaway from most of them is to watch out for sugar, vegetable oils and processed foods in general. For years I've been pretty good about avoiding sugar, but vegetable oils was not something I paid much attention to. Now I'm making an effort to avoid those foods that use any oils other than olive, coconut or peanut. No canola, safflower, cottonseed or vegetable oils if I can help it.