I recently gave a nutrition seminar with a friend and fellow RD.
A gentleman in our audience shared his story about losing a significant amount of weight but hitting a plateau. After some discussion we learned that while he is still exercising quite a bit he is also eating more that he was when he started dieting because he is now living in a retirement community that emphasizes social gatherings, where there is usually food. He told us he has a hard time saying no and a hard time not overeating when he does snack.
First, I recommended he keep a food journal. Writing down (or keeping track electronically) of what you eat has been shown again and again to help in weight loss. It helps us learn portion sizes, portion control, calorie and nutrient content of foods, helps us self-monitor our eating, and helps us find simple ways we can adjust our eating to improve our health. If you haven't done it, I highly recommend it, even for just a few weeks. If you want to do it the new-fangled way, try sparkpeople or myfitnessapal. They are free. And I think they both have smart phone apps. Or you can just do it the old fashioned way with a notepad and pen. Either way works!
I have a basic food journal that I developed. If you would like a copy to use, email me.
Next, my friend and colleague recommended that the gentlemen read the book Mindless Eating by Brian Wansink. She said it might teach him why and how he is overeating and help him learn how to stop. I have not read this book, so I cannot fully endorse it yet. But I did just purchase it online for less than $10 and plan to read it ASAP. I might do a book review when I'm done.