There's always a tension between planning and flexibility in anything you do, really — something I am still learning. I like plans. I like plans so much that I have difficulty jettisoning one even when a much, much better deal comes along. I like doing what I set out to do. Living with children as I do now, I'm having to exercise my flexibility a lot more — to change it from "I have a plan" to "I have a plan, but I can change my mind."
But I'm still heavily biased towards planning. I still suspect, for instance, that the key to developing flexibility is more thorough planning. (Someone somewhere is rolling their eyes at me, I think. But I press on…)
I was encouraging pre-planning in the comments at my friend's blog Confessions of a Fat Loser, because writing out the day's meals and snacks the night before (instead of afterwards) had helped me so much. But of course, what helps one person might not help another, and maybe one of the reasons it worked so well for me was that I get some satisfaction merely from checking off the boxes one by one as I move down the list. Following a plan makes me happy at some primal level, perhaps enough to make up for the loss of the second servings I planned not to have. The other two pieces — applying that to the food I would eat, AND putting the right amount of food into the plan — must never have occurred to me before. Weird, that.
But then, I am sure there are people who instinctively chafe at plans of any kind, even the sort they make for themselves, and hate being hemmed in. I would like to be able to offer a suggestion for calorie restriction and/or intentional eating that meshes beautifully with this personality type, the Plan-Free Diet, but honestly, I can't figure out what to do with it. I keep coming back to …. umm…. restraint and restriction is kind of impossible to do without, even if what you're "restricting" yourself to is on the whole better than what your whimsical, free-spirited self would come up with on the spur of the moment.
Let's look at it this way. As a point of action looms closer and closer, the choices open to you narrow and narrow to the point when you must enact one, and all the freedom collapses into the mere act. If you do not make a choice in advance, circumstances will make the choice for you. The sooner you make a decision about what you will do, the more freedom of choice you will have exercised … because the earlier the decision, the larger the pool of options from which the path has been selected. It's not doublespeak: Self-restraint is liberating. You've seen this in other areas.
So… I just don't think you can do without planning, and still expect to succeed. But you might do better disguising the plan so you can swallow it more easily… or readying multiple plans that you can pick from in the moment… or have a sort of once-and-for-all plan (an algorithm) that requires hardly any thought once you've begun.
Disguising the plan. An example of disguising the plan would be the strategy of "grocery store gate keeper" — keeping the junk out of the house by the simple expedient of not buying any, and making sure there's plenty of healthful choices around instead. (This mostly works for people whose problem is specific "trigger foods" or being tempted by too much nutrition-poor food, rather than for those whose problem is "too much of a good thing" like mine was.) It's still a form of planning ahead — intentionally narrowing choices in the future — but because the plan is removed even further back from the decision points, it may not feel like a plan.
Multiple plans. This came up in one of the other comments:
…[T]he pre-planned menu does have the difficulty that you have to know what you're going to do if it doesn't work, you know, when your menu says 'lasagna' and then you realize you didn't defrost the meat, or that the time got away from you and it is already 6:15, with no time left to make lasagna! This is where I have to rely on a good set of defaults. No matter what, I know I can eat steamed frozen vegetables and beans and rice, or, hard-boiled eggs and salad, or whatever you decide it is going to be. In a home management sense, of course we want to have a nice dinner ready for our family, but it has been important to me to have some 'sure things' up my sleeve for myself. I still do meal planning, of course, but (thankfully!) messing up on my meal planning doesn't have to mean messing up on my eating.
Plan to be flexible in other words! Having something "up your sleeve" — a default — is a backup plan. (And I'll add that it's fine to have a one-person backup plan as well as a whole-family backup plan — yes, the ideal is that the family eats the same foods together at dinner, but when one member really needs to follow a plan for health reasons, it's not going to derail family togetherness if occasionally the backup is "mom has this and kids have that.") But this is really a good practice for almost anyone. My dinner plans don't derail very often, so I don't have much trouble with the occasional "screw it, we're ordering pizza" night, but I have default breakfasts, lunches, and snacks ready at all times; I order them up several times a week.
Once-and-for-all planning (algorithms). These are very powerful for the planning-challenged. An algorithm is a simple, easy-to-remember set of behaviors. Such a simplified set, it is true, may not cause every single meal to hit the nutritional targets that will help you achieve health. But the idea is that the simplified set will bring you in to your target on average — if it is easy to follow, so you aren't tempted to cheat yourself, then over the course of a week or so you'll have met your goals just as well as if you had attempted to micromanage yourself. The classic example of the once-and-for-all algorithm is the No S Diet, which I can't recommend highly enough — it may not turn out to be your thing (it's not really mine), but it is so easy that it is worth a try for almost anyone, especially anyone who is looking for a real lifestyle change and whose problem is mostly excess rather than eating the wrong foods.