Since you've been eating primal, I'd vote for trying the potato thing just in the interest of shaking things up. I tried it for 8 days in November, and although it didn't seem to be doing much right away weight-wise (hard to tell, as my scale died on day 3), I have since broken a major (6-mo) stall/creeping regain and am down another 22 lb after resuming LCHF Primal. I'm now looking to implement periodic potato "refeeds" and random higher-starch days as a useful tool.
Now, if you want to switch that up with something like Gorbag's suggestion, you'd essentially be doing Stillman Quick Weight Loss or Lyle McDonald's protein-sparing modified fast (PSMF)...which have a reputation of being effective, but you may feel like total crap (watch your electrolytes!) and these low-carb/low-fat plans are very hard to stick to for long.
6' 2" | Age: 42 | SW: 341 | CW: 198 | GW: 180?
“Life can only be understood backwards, but it must be lived forwards.”
― Søren Kierkegaard