I'd love to see your grocery bills before and after this change, adjusted for inflation. High carbs = cheap food, thus the seeming contradiction of obesity even in low-income households.
Advocates of this stuff always remind me of Oprah, et al breezily giving advice along the lines of "just have your personal shopper and chef..."
I don't have grocery bills plotted against inflation, but my grocery bill runs 6-700 a month for a family of 4 and has since 2011 (so saith Quicken). From my limited data, it doesn't seem like it cost more, just changed what we bought. Maybe the pork chops I had for dinner cost more than box of pasta and jar of sauce, but the eggs and bacon I had for breakfast were cheaper than the cereal and fruit, so it's kind of a wash. Pork, chicken, various nuts, eggs, butter, lots and lots of bacon. These things are not hard to find or cook. No personal shopper or chef required.
I had similar results as gosand, but it's not for everyone (the wife does terrible on high fat/low carb). For me it made a tremendous difference in everything they can measure about my health and I'd never go back. It's a shame that for decades a diet that could really help some folks has been demonized.