Recently we experimented with going gluten-free for a month. The good news is that really it wasn't as difficult as you'd think. By approaching it from a 'let's focus on what we can eat' mindset, there are so many clever options that don't include gluten or rely on expensive commercial 'gluten-free' substitutes.
Most people know that they shouldn't be eating the convenience food that's so readily available in shops and supermarkets, but they don't know how to break the habit. You don't need someone to tell you the damage that putting away numerous biscuits and chips will do. You want someone to show you how it's done.