I'm not familiar with the diet with which you refer, so I did a quick search... The first thing I find is that it restricts calories to about 600/day, which puts up a red flag immediately for me.
Of course, you can probably lose weight on any diet that only allows 600 calories/day, but can you stick with it? And is it healthy? My little bit of research shows that ketogenic diets are a bit controversial as to how healthy they are. That seems to be one of the drawbacks - most people can't stick with it because of the restrictiveness. It's certainly not something I would try even if it is suggested by a nutritionist because I don't like anything that seems too radical and of course, I'm sure it's not inexpensive.
All of that said, let's look at your health issues. I'm going to zero in on the thyroid/goiter first because there's a good chance that might have something to do with your weight since the thyroid controls metabolism.
Are you sure you're on a high enough dose of medication to get/keep your thyroid levels (Free T4/Free T3) where they should be in order to help promote weight loss? If you've had recent thyroid tests done, I'd be interested in knowing what your levels are. Just having levels "in range" isn't good enough; most of us find that we feel best with Free T4 about the middle of its range and Free T3 in the upper half to upper third of its range.
Another issue I might worry about in your case is whether or not you could have insulin resistance/pre-diabetes. Entering a state of ketosis if one has impaired glucose tolerance can cause glucose levels to drop too low.
Both thyroid and insulin resistance/pre-diabetes can affect blood pressure.
So then we move on to your current diet and exercise...do you eat a healthy diet, to begin with? Your body needs all the food groups in order to get adequate nutrients and some of them, such as A, D, E, K are fat soluble, so you even need fat in order to absorb/use them. This means that cutting out fat and going with a very high protein diet is not necessarily the way to go... My doctor put me on a high protein diet and I gained MORE weight :-(
That said, some of us have food sensitivities we aren't aware of, so we do have to eliminate certain foods, but that's another issue.
I've been told that the Mediterranean Diet is one of the best there is... It incorporates plenty of fresh fruits, veggies, fish, chicken and other meats, nuts, seeds, and all the other things that are most healthful. Eating the freshest, unprocessed food we can is always the best. Anything you buy in box/package is not as good as what you buy in the produce or meat section.
And then there's exercise. Even a short walk around the living room, the yard, the block a couple of times/day is better than no exercise. Exercise can also help your blood pressure.
The first thing to find out, if you can, is how much money the nutritionist is getting paid by Pronokal. It may be nothing, but I doubt it. Doing a quick check on the website of the company, they are selling their products. Anyone can go on a high protein diet, anyone can then add in more of their regular foods later on, and anyone can then go back to eating whatever they want in a third stage. What these programs do, though, is some people just won't do it themselves and for those people a program can substitute for the discipline they lack. This particular diet seems a bit better than others in the sense that it isn't requiring an unhealthful high protein diet forever, just until you lose your first batch of weight, then it changes by opening up what you can eat. Now, there's no way to know if it works or not, because the data on the website is extremely short-term, a failing of pretty much all high protein diets -- the issue isn't whether they work, they do, the problem has always been that the weight loss doesn't last because eating higher than healthful amounts of protein has to stop at some point and then you go back to where you started. So your thought that losing slower is better is generally thought to be correct because it implies a permanent change of diet and exercise that will hopefully keep working, though even with this people do plateau and have to make further changes to lose more weight. Judging from the program, if it's true, and I never trust proprietary websites, because this one does guide you back to a more normal way of eating -- unfortunately they don't describe what that is -- you're not staying permanently on a diet too high in protein and too low in essential fats. You're obviously going to have to choose, but I do find it odd that a nutritionist doesn't just recommend a diet for you and instead recommends one you have to buy -- again, my suspicions are raised that this person is making money doing that, which might skew your trust in this person. But as the above has already said, the longest-term ongoing studies of human health show that eating a balanced diet of complex carbs, lots of veggies, and limited animal fat with most of it in the form of fish (which, you should know, the fattier the better, fat isn't the enemy, it's the kind of fat that's the problem, just as carbs aren't the enemy, it's the kind of carbs) leads to communities with the lowest levels of obesity and the longest healthiest lives. These diets are grouped under the term Mediterranean Diet, but it's not just one diet, it's a way of eating. But again, if you have to lose weight quickly, high protein diets do work in the beginning better than this longer-term approach, and if you are doing any resistance training as your preferred form of exercise, higher protein is necessary to see results in increased muscle. This is a long way of saying, who knows? You're going to have to make a choice but discipline and lifestyle changes are probably going to be the key unless, as also stated above, your health problems are a cause and aren't being properly treated at the moment. You know, nobody's ever topped eat less, move more!
"You know, nobody's ever topped eat less, move more!" LOL We've kind of been down this road and I'll skip down it briefly one more time - not as an argument, just as a reminder - unless that thyroid issue is treated optimally, the O.P. can eat less all she wants and although she will probably, eventually, lose some weight at only 600 calories/day, she will also get much sicker than she already is. I've, personally, gained weight on fewer calories, more exercise.
I agree (and should have said) that the Mediterranean diet is not a single diet, but a way of eating. There are a number of books/articles one can read about it, but Paxiled explained it quite well.
Safe weight loss is generally considered to be 1-2 pounds/week. Anything more than that is, often, difficult to impossible to maintain because it's likely accomplished by impractical or unsustainable means. Most of us didn't gain all our weight overnight and it's not practical to think we should be able to lose and keep it off in a short time.
Hello, and thank you very much for your detailed answer, I really appreciate it. I will try to comment on your points in order.
Thyroid: I have thyroid goiter diagnosed about 20 years ago, it is considered asymptomatic for the last 10 years, with all nodules being "cold". All my thyroid results have been normal all the time, even at the time of diagnosis, for one year I was off any medication, but did not feel well and my TSH went up to 2.6, currently it is 1.18. Free T4: 15.76 out of range 10.90-22.20, free T3 : 4.63 out of range 3.1-6.8. While I do feel that thyroid could contribute to my problems with weight, the clinical picture always has been quite normal.
Glucose 5.5 (out of 4.2-6.2), cholesterol 4.66 (0-5.2), HDL 1.8 (0.9-2), LDL 2.4 (0-4).
Taking supplements : Omega 3 & DHA, Evening primrose, D3/k2, Taurine, Benfotiamine and Alpha Lipoic Acid.
Diet: almost no processed food, I am a good cook and cook at home 95% of the time. When eating outside - no fast food. No sodas, no cookies. Eating quite a lot of fruits, not that much of vegetables, but always having some with the meal. I am 5'11", and gaining almost steadily around 10 lbs (~5 kg) every two years in the last 6-7 years.
Exercise: walking 3-4 times a week about 3 miles for about an hour. Will be swimming in the lake regularly once the lake we live next to is warm enough. Occasionally go to gym, but should do it more regularly.
Overall I have a relatively sedentary but not horribly unhealthy lifestyle.
Nutritionist: obviously she is paid and gets some commission from Pronokal, I have no big problem about it. If it works, if the nutritionist gives me more or less objective information for me to make the choice, I would consider it relatively fair game. As usual, there is very little info on Pronokal website, I know Spanish a bit, googling in Spanish provides many websites with sad stories from people who did Pronokal. But I have not found anything really drastic - as I said, many people rebound, especially the ones who eat a lot of fast food and were missing it during the diet, quite many people had some complications and had to stop the diet earlier. No stories about heart attacks or similar grave consequences, but it could be just a selection bias. I will continue searching and reading. Some people manage to keep the weight off for a few years at least.
Pronokal -- very intense original phase with 600-800 Kkal per day, almost all coming from proteins in liquid form. It seems to work, meaning that people do lose a lot of weight if they manage to stick to the diet for 2 months.
I am considering the diet because I ran out of the alternatives -- I cannot exactly trace why I keep getting on weight. While I do not adhere to any diet, I think I do eat relatively healthily, the problem should come from very slow metabolism. I've tried to kick it incot action (intermittent fasting or the opposite, eating every 3 hours), did not seem to work.
I know that the healthy loss of weight is 1-2 pounds/week. With Pronokal it is much more dramatic, with major losses coming in the first 2 weeks of the diet (4-5 pounds of which I think would be water). But the speed of the weight loss with Pronokal is too fast, seems to be too unhealthy, and doing it for 2 months seems to be too drastic. Pronokal puts you in a deep ketosis, and keep you there for 2 months. My question is: why not to do this type of diet for 2 weeks, then let your body to adjust (and perhaps to get used to) your new state, perhaps to gain a bit of water and weight back, and then repeat this operation 4-6-8 times, as needed. My reasoning is that it could be milder on the body, less taxing for the kidneys. Perhaps it would cost more, but right now I am not considering this side of the diet.
Also, my cardiologist thinks that if I lose the additional weight I carry, my blood pressure can normalize on its own. I hope he's right. So is it worth the risk (including cardiovascular) to try and go through the Pronokal diet to get to the optimal weight where supposedly I will have better heart conditions?
Thank you very very much for your comments!