I believe there's a fair bit of evidence to the effect of, any "diet" that restricts one's food options - be it calorie restriction, low fat, low carbs, low protein, intermittent fasting, no sugar, whatever - will result in weight loss as long as it's stuck to. Which makes sense logically; if normally you'd eat whatever you felt like, and then you restrict what (or when) you're "allowed" to eat, some substitution will be done, but you'll likely also just eat less.

And then when you go off the diet (either intentionally, or more likely, by just slowly drifting back to the norm), you'll return to eating what you were before, and will return to your original weight. Which is why the only diet that works is one you can stick to indefinitely. So, if the parent can stick to a no fat, high complex carbs diet for life, it will probably work for them.

I’ve been a fan of the keto diet (low carb high fat) for a while. But I suspect any diet that cuts a very large group of foods like carbs or fats out forces you to be more mindful of what you’re eating. And that’s a large part of the weight loss on those diets.

Elsewhere in this thread it was stated that food journaling was the gold standard in weight loss, which also I’d expect to increase mindfulness around eating.

How complex are pasta, rice, pint of blueberries, 5 medium apples, 2 mangoes, and a pound of grapes?

Pasta, rice, and fruit have huge amounts of simple sugars.

After 2 years, my blood pressure went back down to a steady 110/75, heart rate about 55-60, bad cholesterol is on the low of normal range. I do about 2 hours of cardio with light weights per week, no longer lift. That's not a lot, but it's enough to stay at the same blood pressure for many years now.

I don't do high carbs - fruit are not high in carbs you actually process. I eat normal portions of complex carbs like bread and pasta, normal sized meals. I eat a ridiculous amount of fruit, and that has some sugar in it, but it's actually not that much. What that does is increase my fiber intake to ridiculous levels - and that has many benefits.

My issue was that I use food as an anti-depressant, and to deal with stress. The solution had to involve eating a lot, but minimizing calories. That's why the fat had to go - I can eat twice as many carbs as fat for the same weight. When you look at things like fruit - a lot of those "carb" calories you don't even metabolize since it's fiber.

I don't think I have discovered some magical solution, but it works for people like myself, who have what I consider a minor mental illness called 'self-medication with food.' Mental problems are a lot harder to fix than just not using oil and replacing nuts and chips with fruit. My solution to win the war was not to fight it and learn to live w/ the fact that I'm not perfect, and adjust the lifestyle to that.

High carb diets are a bad idea. I eat normal balanced meals, just with no fat. Long-term high fat diets are for people who want liver damage, and stop eating when they're full. A little bit of fat makes you full, unlike carbs. But keto is terrible for your health if you do it for decades.

The tiny amount of fat I do get, is from things like red tuna and other low-fat fish. It's amazing how little good fat you actually need in your diet, if you look that up. Literally one can of chunk light canned tuna is all you need for the day.

Now here's something groundbreaking that's pretty good - thin and wide no sugar no fat pancakes: 1 cup flour, 3/4 cup fat free fairlife milk, 2 packets splenda, 1/2 cup Egg Beaters. mix real well so it's runny with no flour chunks. no need for baking powder. real short spray of oil to just get some drops on a teflon pan. no need to spray when you flip.

Now my diet is not high carbs, but let's address the "no fat+high carbs = bad." the reason that's everything you've read in the last 20 years, is because that's what you chose to read. there are different diets for different causes of fatness in people.

fat makes you full faster so helps you eat less calories. carbs make you work out harder, so you burn more calories. if you have an active lifestyle - carbs and no fat. if you sit on the couch after sitting at the office, you want fat and no carbs. dietary fiber isn't something you should count as carbs.

if the reason you're overweight is because you like to constantly eat, and it has zero to do with hunger - you don't want any fat. you want the most amount of food for the least calories, and fat is double of carbs per gram. you want lots of indigestible fiber a normal amount of carbs, and eating the potatoes with that thick rough skin, with the skin.