One of the first things to get compromised with met syndrome is the liver. Years of fructose/alcohol/etc... overload causes severe hepatic insulin resistance. One way to combat this and get the liver back to it's old ways are to limit carbs of all stripe to ketogenic or near-keto levels.
Once the visceral and fatty-liver fat is gone, liver function starts returning to normal, then you can start eating the starchy/sugary things which grow upon the earth.
It may take years for liver function to return to normal, a good indicator is triglycerides and blood glucose. In cases where these are impaired to any degree, it is probably best to limit all carbs. Once metabolic markers are showing insulin sensitivity and better control, it is probably wise to add in starchy carbs first, then sugary ones after some time to ensure proper glucose control and insulin sensitivity.
I think getting stuck in a LC rut for years does no one any good and adding carbs needs to be a pre-defined criteria once metabolic syndrome is showing signs of complete reversal.