Dr. McDougall has a saying that this is not an 'all or nothing' plan. The closer you come to 100% compliance, the better you will do - but - you will still see results even if you are 90% compliant, too.
For me, while this is undoubtably true, it leads to a dangerous 'quagmire of compromises' where it's easy to get stuck with bad choices like diet salad dressing, diet coke, vegan coffee creamer, commercial peanut butter, Earth Balance, white bread-rice-pasta (sorry Dr. M we'll have to agree to disagree on this point), etc. which we end up buying and eating to avoid a worse choice - even when a BETTER choice exists.
I think a better term than 'MWL-legal' or 'on-program' or even 'allowed' is 'health-supporting' because it removes the concept of 'diet food' and replaces it with 'healthy food'. When I bought the first McDougall book 'The McDougall Plan' back in the 1980s, I also picked up Mary McDougall's first cookbook which was titled 'The McDougall Health-Supporting Cookbook' and that term has stuck with me ever since.
When shopping for food or even condiments, I utilize this term as I read the labels. Will this food support my OVERALL health is the question I ask myself, NOT will this food speed up my weight-loss or -alternatively - feed my addictions (ie make me feel temporarily better about my stupid boss/husband/wife/child).
Weight-loss is only one aspect of health, and although its an important one, it can't be your only focus or you'll be drawn away into the next Internet diet you stumble upon. It HAS to be about your health.
A good rule of thumb for determining if a food is 'health-supporting' is if you look at a label and it contains ingredients you couldn't locate without a chemical supply catalog then put it back on the shelf. If it contains oil, put it back on the shelf, if it contains more sodium per serving than calories put it back on the shelf, if it contains animal products, including casein from milk, put it back on the shelf, if it contains high fructose corn syrup or artificial sweeteners, put it back on the shelf.
Emily Boller who blogs on Dr. Fuhrman's Diseaseproof.com blog did a post a while back on the powerful snare of compromisehttp://www.diseaseproof.com/archives/em ... omise.html
It ends with the phrase:
Seeds of compromise sown into the soil of our lives will eventually produce a harvest of addiction. Guaranteed.
Indeed they will.