Most of the problem isn't with science, but with reports in the popular media. You're not going to learn much about a study in a 30 second TV news report, which will often present a finding as though it's now conclusive, and which won't often tell you much about how extensive the research was, or its methodology. Nor will they tell you that most findings are not going to be something set in stone like a law of physics. Medicine in particular is a field where findings are continually revising what we know about human health. Some people can't tolerate the grey areas inherent in the field, and decide that it's all lies. It's a shame.
Ultimately, eating a low number of calories and getting adequate exercise will keep most people at a healthy weight. It's hard because until very recently, it was a fact of life that some years would be bountiful and others would have very little. Our survival as a species was once predicated on eating all that we could when we could get it, because there would be times when our fat would be what kept us alive through times of famine. Modern agriculture and modern food trade don't just ensure that we always have food regardless of the weather, in the industrialized world it means that we have too much food. And we do what our instincts tell us to do - fatten up for the crop failure that could happen next year. People tend to frame it as a moral matter (and certainly at one time the gluttony of a few could spell disaster for the tribe), but few question how it's possible that our actual gross tonnage of food per American has grown so dramatically over the past 70 years or so, and why "individual" portions are so much larger today than they used to be. A Quarter Pounder at McDonalds was once considered to be a big burger. A Coke was 8 ounces. A drumstick was a full main course. The greater availability of food just means that it all has to go somewhere, and that's not straight to the landfill. At some point, we'll have to question how we're managing our agriculture.
These are just some of my thoughts, and aren't meant to claim some kind of authority on the topic on my behalf.