There are so many pseudoexperts, and so much misinformation out there on nutrition - including in this thread. I am a professional (registered) nutritionist with an advanced degree, have worked in hospitals for many years and have seen thousands of people with all types of ailments, from heart disease to gastrointestinal cancers to eating disorders, and have read thousands of studies over the course of my education and professional work. It's unfortunately difficult to change peoples' perceptions on certain foods as food choices are a deeply personal decision, and I hate debating nutrition on the internet because of this. But here goes.
I never recommend the ketogenic diet. Ever. There's multiple reasons for this. First and foremost it cuts out the healthiest foods that you can put in your body - beans, lentils, fruits, certain vegetables, some nuts (depending on how you plan things out) and nutritious grains such as quinoa. Second, it is has not been shown to be superior if the long-run - which is what matters - than other "diets" for weight loss. Third, it's often inadequate in certain micronutrients (such as potassium, which is actually vastly underappreciated, and others such as folate and magnesium) and inadequate in fiber (not technically a nutrient, but also vastly underappreciated in its role in human health). Fourth, from biochemical and physiological standpoints, combined with observation data, the ketogenic diet stands on shaky ground. It's not just heart disease that is of concern, but increased risk of other ailments such as colorectal cancer. Fifth, few people are knowledgeable enough, or dedicated enough, to actually tailor their daily diet to reach and maintain a true state of ketosis. Sixth, weight loss is great, but it by itself is not a panacea, and you are still at risk for developing medical problems if your overall diet is unhealthy, especially if compounded by other factors (stress, lack of sleep, smoking, etc). If your weight rebounds because you couldn't maintain the diet, then you're actually worse of than when you started since large scale weight fluctuations have a negative impact on your health. Seventh, the potential benefits do not outweigh risks or the effort involved to follow the diet. You can achieve the same weight loss goals while including all foods. There are more reasons but that should suffice. A ketogenic diet is medically indicated is for epilepsy or perhaps other neurological conditions but otherwise it's not a good idea.
A nutrition pattern (I hate the word diet) that is predominantly - or exclusively - plant-based is far superior. There's not only growing scientific evidence of this from observational and clinical data, but it makes sense from physiological and biochemical theory as well. Of course you don't have to be a vegetarian/vegan to be healthy, but if you want to offer your body the best chance of remaining healthy (nothing in health or medicine is certain), or reversing/managing certain chronic diseases, then a plant-based diet is the way to go. I'd bet my entire bank account - hell, I'd bet my life - that if every American adopted a plant-based diet overnight and stuck with it, that you would see the prevalence of the top killers of Americans - heart disease, cancer, obesity-related conditions such as diabetes - plummet dramatically. Flexitarian can work, and the Mediterranean pattern is very good too. Just like any nutrition pattern, your food choices need to be balanced. And ultimately, just do what works best for your body. A co-worker of mine is vegetarian, she tried being vegan for a while but for some reason felt low on energy without some dairy. So she's lactovegetarian and does just fine this way.
It's also a bit sad that some people still think that you have to eat tofu (or some other generally unpopular item) or you're out of luck. True, there was a dearth of convenience vegetarian/vegan items not long ago, but today there are tons of options - plant-based yogurts, ice cream, cheeses, protein bars, meat substitutes - along with the true staples of a healthy eating pattern (vegetables, legumes, etc). There's also an abundance of websites dedicated to plant-based cooking with incredible recipes. I don't even need to list them because google will help with that (but I certainly can if needed).
With regard to Danny, I believe I read somewhere that his hypercholesterolemia is genetic. Some people cannot achieve normal cholesterol numbers even with a good diet, exercise, and other lifestyle changes. But what he is doing cannot hurt. Good luck Danny.