For a lot of people - those who are simply overweight, perhaps just barely clinically obese, it's entirely possible that his plan will work just fine. It'll probably still improve things for those who are morbidly obese - assuming that they're currently eating SAD (or whatever the equivalent would be called in the UK), which is full of lots of starches and sugars, because this plan drastically cuts back on those. Even the diabetic who's been eating 300+ g carbs daily, if they cut back to 100ish grams carbs, that will improve things significantly. They'll still be on insulin, their blood sugar will still be higher than ideal, but at least their blood sugar would be under somewhat better control. (some article on here mentioned that good blood sugar control was 140 to 180 - still quite high, but not totally out of control, such as if it was 350 or 400) It appears that's the kind of situations he's really trying to help. It will likely seem like a drastic change to those people, so I can't imagine too many with diabetes or metabolic syndrome going directly to 20-30 g/day - the induction flu would be awful.
So in that way, his plan makes sense, even if still too many carbs for a lot of us on here.
However, I keep reading his plan, and I have a problem with it.
Three meals per day maximum, and eating only until you feel full. Take your time eating, eat with others if you can and enjoy your food.
At least two to four tablespoons of extra virgin olive oil daily.
One small handful of tree nuts (walnuts/ almonds/hazelnuts/ macadamias) daily.
At least five to seven portions of a variety of fibrous vegetables and low-sugar fruits a day (see below). I suggest a maximum of two pieces of low-sugar fruit and/or one medium-sugar fruit, and at least five portions of vegetables a day. Fibrous foods tend to make you feel full for longer, reduce a rapid rise in blood glucose and insulin and are good for gut bacteria (the microbiome).
Vegetables in at least two meals daily.
Oily fish (such as salmon, mackerel, tuna, herring and sardines) at least three times a week.
Actually a few problems.
Eat only until you feel full.
I'm pretty sure I'm not the only one on here who has an extremely delayed feeling of satiety. He says to take your time eating meals, apparently so that you sense fullness and know to stop eating. I'm afraid I'd need to stretch a meal out to about 1-1/2 to 2 hours to feel properly full. And that might not work - I've never tried it. But there are times when I eat what seems like a proper amount of food, and still feel very hungry, but stop anyway. But then rather suddenly a couple of hours later feel excessively full.
One small handful of tree nuts daily.
Ah, if only I could stop at a small handful - for me, tree nuts are incredibly addictive, and I just don't have an off button until they're all gone. The only way that's going to happen is if I only have that one small handful available, period, which would mean going to the store daily to buy one small handful of nuts, and while there, resisting buying enough to last week... and end up with it only lasting a day.
Fibrous foods make you feel full longer.
Maybe this goes back to my delayed feeling of fullness, but I don't see a bit of difference in how long I feel full on fibrous foods, as compared to protein and fat, unless it's that the fibrous foods don't seem to last quite as long as protein and fat. It's not that I don't eat veggies, I just don't see that they help me feel full longer.
Oily fish at least 3 times a week.
This makes some sense for the UK, a relatively small island kingdom, surrounded by the sea, where fish are going to be a readily available part of the diet, but not so much if you live in a landlocked area, where fish and seafood need to be shipped 1,000 miles. If they're all canned, it can still be a problem obtaining enough to have it that often (depends on where you live, and what's available)
There's also the issue of mercury in seafood - in the US, we're being told to eat no more than 2-3 servings of fish and seafood weekly, and stick to the ones lower in mercury, where as he's recommending at least
But the biggest problem I have with that part of his diet is... where's the meat? What about eggs? Chicken? Lamb, Pork, Beef? Is he only allowing fish as a protein source? And if he's only allowing fish, does that mean he's only allowing 3 servings of protein weekly?
I'm hoping that he encourages other protein sources in his book - for that matter, I hope he's allowing some other dietary fats beyond the 2-4 T olive oil daily, because some butter or cream would certainly help those veggies be more satisfying for a longer time. I'm hoping that whoever wrote that article was simply (and unfortunately, very typically) showing an anti-meat bias by leaving out any reference to animal foods other than fish.