The diet I'm including in my answer is safe, but has a marginally higher daily calorie intake. It originated with a Dr. Tran in France about 30 years ago, made it to Canada, and about two years ago was approved by the FDA for the USA. It's typically administered by doctor's offices or health clinics.
Ideal Protein Diet
It operates on the basic principle that the modern diet typically has far too much sugar and other insulin inducing chemicals. As a result, our pancreas gets overworked and produces too much insulin (trapping the calories as fat and making you hungry again). The diet consists of four phases:
- Phase 1: let the pancreas rest and lose weight. (80-90% of weight loss goal)
- Phase 2: get the stomach used to digesting more whole proteins (remainder of weight loss goal)
- Phase 3: reintroduce carbs safely.
- Phase 4: maintenance
You are given a metered amount of protein, required to eat a certain amount of vegetables, drink at least 10 cups of water, take dietary supplements, and keep a food journal for the administrator to review. On phase 1 you get about 900 Kcal from the food, with the balance of your daily calorie needs coming from your fat. The protein is sufficient to protect your muscles and organs, but not enough to exercise strenuously. I.e. keep your heart rate in the fat burning zone only if you want to work out. You will eat four meals a day. Your plan meals come in protein packs which are fairly good, all things considered.
For breakfast, you have a protein pack. For lunch you have a protein pack and 2 cups of green vegetables. For dinner, you have your own protein (5 oz lean beef/chicken, or 7oz seafood) plus 2 cups of green vegetables. Snack is another protein pack.
The protein packs come in the form of soups, cereal, pudding, drinks, etc. You can have coffee, but every cup you drink requires another cup of water.
Our plan administrators have noted that many women are protein deficient, so when they are on the plan they will actually gain muscle mass. Me, being a guy, did not experience that side effect--although my wife did. Average weight loss according to the plan is 3-5 lbs/week for women and 4-7 lbs/week for men.
Additional note: any plan that simply limits calories without a sound medical backing will cause you to lose muscle mass. Muscle mass is what enables you to burn fat. When you go off the diet, you will not only gain the weight back quickly, you will gain more than you lost. That is why you need to be smart with the calories you take in.
This plan is monitored, and it helped me drop 85 lbs in 5.5 months. My wife is still on it right now and she is losing a bit more slowly (70 lbs in 6.5 months so far). I did have some problems with constipation, but that shouldn't be a surprise considering almost everything with a decent amount of dietary fiber also has carbs and is forbidden in the first phase.
It really helps being creative with your veggies if you are going to be on it for some time. There were a couple of lower weight loss weeks (1-2 lbs) and some towards the beginning which were much higher. It's best to be concerned about the inches more than the scale. When gaining muscle, the inches get smaller even though the scale doesn't move much.