If I had the ability to make you listen to just one thing I say, and to follow through with it, I would say it is this: CUT GRAINS. In every form, grains are not our friends.
Sure, drinks/foods with added sugar are bad, but many of those tend to be grain-based. Most meat (with the exception of bacon and sausage) tends to be sugar-free, and most vegetables are better for us than any grain.
With that said, if you only listen to two things I say, I’d add “Anything with added sugar” to the list.
Cutting grains and anything with added sugar will yield you the most impact on your health and weight. Just cutting out sodas alone can help you lose around 2.5 lbs a month. The more sugar you cut, the more weight you will lose. Give it a try.