Rob Kardashian & Blac Chyna: Cocktails and Carbs for Lunch

Rob Kardashian and Blac Chyna want you to believe he's in the throes of a crash diet, but get a load of his carbo-load and the booze to help wash it down.

Rob and Chyna hit up Benihana in Encino for lunch Tuesday ... and our Far East sources tell us they wolfed down a "whole bunch of sushi," as they sipped on a couple rounds of sake and mimosas.

Rob's had issues with substance abuse, and Chyna's fresh off a daytime arrest in Texas after getting wasted at the airport.

That said ... it looks like Rob's losing a bunch of weight.

The Benihana diet. Who knew?