I sometimes keep a food journal, mostly if I see a change in the way my clothes are fitting, lose energy, or any other noticeable physical sign that my diet may be out of whack. When I journal, I’m pretty strict about logging everything, because I want to find out where the deficiency is. Usually a couple weeks is all it takes to get back on track. It’s also a good way to evaluate some of the newer tools out there! A coworker of mine recommended MyFitnessPal (I use it on my Android phone) and it’s remarkably easy to use and very comprehensive in what foods are in the database. Within 2 days I recommended it to a client and she loves it!
I think it’s a very helpful tool to motivate and educate clients, and it’s a way for them to take ownership of the process of physical change.