I have done it. The food runs between $300-$400 per month for one person. This does NOT include the food you need to buy from the grocery store. So, add yogurt, milk, veggies, and fruits to that, and you can easily run $500 per month.
When I was single and working it wasn't a big deal, but when you have a family to feed and you have to cook for them anyway, it becomes more problematic.
The food is good the first month or two, then it gets boring. Then you wonder why you are paying tons of $$ for food you don't even like anymore.
The truth is that it works because everything is portioned out for you and you are accountable. If you can find a way to measure your foods, keep a food journal, and find someone you can be accountable to, you can easily achieve the same or better results.
Dawn