My diet was pretty strict for several years before my surgery. It helped for a long time, but wasn't much help in the end. Low fat, no greasy or fried fooRAB, no tomato or citrus products, no spicy, no onions or garlic, no mint or peppermint, water and soy milk only to drink (no coffee, tea, carbonation, caffeine, etc...), no dairy, no raw fruits and veggies and of those I cook, easy on the gas producing fooRAB, no alcohol or nicotine (never been a drinker or smoker). I was diligent on this for years. That is being honest. If you cheat on the diet, you have to pay the price with the reflux. For me having life-threating symptoms was a HUGE incentive not to cheat...and my reflux was irritating my lungs so badly that it had become life-threatening.
I had tons of tests done at about 3 years apart. The first sets showed severe reflux, the second set prior to surgery showed extremely severe. My second Manometry I had showed how poorly my LES really was functioning. It had gotten significantly worse over the years. That is a physical problem. If the LES doesn't close at all, food and acid will make it back up regardless of how careful your diet it followed.
I can say that since surgery I've added an occassional "cheat" into my diet when I'm feeling well, but I still basically follow the anti-reflux diet as my standard even over a year after surgery.
I also still sleep on an incline.