If so, obesity should be cured by avoiding carbohydrates altogether, but can the defect ever be cured, so that carbohydrates (good ones that is) can again form a large part of the diet, or ought the dietary ratio: 1.0/3.0/0.5 (P/F/A) be adhered to permanently
I have about 5% body fat. I dropped to that from 10% when I dove headlong into the Paleo lifestyle in August. Now, I NEED carbs, at least to some degree. When I first began Paleo, I had maybe 20g of carbs or less for several months with no ill effects or cravings. The cravings really do get fairly nasty now. This is a function of my low baseline leptin since adipocytes secrete leptin, and I have very few adipocytes. High carb load raises insulin which stimulates adipocytes to secrete leptin which tells my brain that I'm full, satiated, packed with nutrients & nourishment, etc.
If you have poor insulin sensitivity, you will not produce leptin as you should because a greater amount of insulin will be required to elicit the same leptin response as that required in a more insulin-sensitive person. Before Paleo, a potato or two would make me feel like crap for the rest of the day. Now, I eat a huge sweet potato or yam (1 tsp cinnamon, 1/2 tsp ground cloves thrown in food processor with steamed yam -- tastes exactly like pumpkin pie, thank me later) after every workout, and I feel great. This was n=1 proof positive for me that Paleo restored my insulin sensitivity to a biologically normal state.
I'm only 22, though. I didn't accrue TOO much liver or metabolic damage as a result of my previous diet. If you're older, you have likely accumulated more damage to your liver and insulin system and metabolism in general. As a result, it may take a great deal of time to restore your insulin sensitivity to the point where >100g of carbs a day, let alone in a meal, doesn't make you feel like shit.
Just fast, sleep ad lib, build strength, take long walks at least 3 times a week, avoid stress and keep happy and positive, and eat very low carb for several months to a year, and you can expect your metabolism to recover about as much as it's going to. Don't forget to watch your mood and stress level -- Paleo isn't all about food and exercise. Much of our biochemistry is regulated by neurotransmitters which YOU control by taking command of your life and attitude! This has worked wonders for me.
I'd say the real defect is that the US Government subsidizes grain and its processing so that unhealthy goods produced from those commodity crops are artificially cheap and can be exported world-wide.
It depends on how much damage has suffered your metabolism. If obesity has come (as often happens) together with diabetes, hypothiroidism or other serious ailment, it is unlikely that you can go back to a diet heavy on carbs. If your metabolism is still OK you will be able to go back to consume potatoes or white rice!
Between the grains, sugar, antibiotics, pesticides, preservatives, and various other chemicals in processed foods and our conventionally raised meats who knows which of these ingredients or all of them together are causing us to get sick and fat. It sure is despicable that it's been allowed to develop into what it is though.