On the NY Times opinion pages today there are some examples of how making the "default" option, is the path most people take.
...if T.G.I. Friday's is really serious about helping to change American eating habits, it can do more. Specifically, it can offer the smaller portion as the “regular” and allow customers to order “supersized” portions for a higher price. Although the two portions wouldn’t change in size no matter what they were called, research evidence suggests that labeling the smaller portions “regular” will move far more people to order them than if the portions were labeled as they are now.
...the “paternalistic” decision to make the small portion the standard one would almost certainly increase the number of customers who “choose” it by a wide margin. And the availability of the “supersized” portion would give people an alternative that satisfies libertarian concerns about freedom of choice. I suspect the same is true when it comes to the choice between mammography and M.R.I., though of course the stakes there are much higher.
Check out the article, it clearly states the case for making the "healthier" option the regular option and most people will choose it. If works with 401(k) contributions.
It will work with food.