There is a book out there by this title, but Mary J Shomon. It means diet in the sense of this is what you eat, period; and not as this is how you lose weight. However it does work to lose weight too, especially for those suffering from hypothyroidism. The main points of which, as I remember them that is, I wil summarize here. I really need to get this book back out for myself too, as I won't be using these diet shakes for the entirety of my eating!

1. Lean protien. A diet rich in lean protein sources is a must. It's a little harder to digest red meat than white, which means lean towards white meat and fish whenever possible. You will need to eat at least 30% of your dialy calories in the proteins.
2. Fresh fruits and vegetables. Frozen works pretty well too, just avoid canned. A lot of the nutrients are leached out of your fruits and veggies in those cans. Look for high water and high fiber content fruits and vegetables, and avoid those high in sugar (such as bananas and grapes) because those with the higher glycemic load can cause blood sugar crashes and turn an all ready low energy person into a real sluggish person. Avoid soy beans/endemame. Look to be getting at least half of your carbs a day from fruits and vegetables
3.  Whole grains. When you eat starchy foods, make sure they are from whole sources. Eliminate "white" from your diet. Whole grains will have more fiber, which will help your digestive track work better. Watch out for a gluten intolerance (Celiac's) symptoms! Including bloating and water retention. Less than half of your daily carbohydrate intake should be from here. Carbohydrates should make up about 40-50% of your daily calorie intake.
4. Eliminate soy. Soy beans, tofu, soy crumbles, etc. all need to go. The only soy you can have when hypothyroid is soy sauce. Fermented soy is okay as the enzymes found in soy are deactivated during the fermentation process. Certain enzymes found in soy beans can digest your thyroid hormones from your meds, causing a reduction in the effect of your meds!
5. Water. As in any diet, water is very important. At least 8 8-ounce glasses a day are recommended. It too, along with fiber, helps keep your digestive track working like it should.