If you're gonna convince them to fix their diet tho, you need to spend some time on the subject. Everyone needs to understand the syptoms of carb withdrawal & be committed to sticking to it for a month or two. Sugar addictions are a hard thing to break.

Shawn Baker, Kelly Hogan, & SteakandButterGal are all good sources of info. If you want a milder appraoch "It Starts With Food" is a good read. But I am most clear headed with steak & eggs & not much else. Almost always <30g of carbs in a day, with rare exceptions. If I eat any carbs they usually come from plain whole milk yogurt.