I can't exercise either so I know the problem.
The ND diet is basically 800 calories a day. The original experiment utilised 3x 200 cal diet shakes. Due to constipation they then added in 200 calories of veg a day. Dr Michael Mosley then wrote a book called the Blood Sugar Diet based on the ND study but using real food. But, basically, it really all comes back to eating 800 calories per day for 8 or 12 weeks then slowly increasing until you reach a calorie level that maintains your weight.
I found Michael Mosley 's Blood Sugar Diet the most helpful.