With a strict elimination diet it quickly becomes impossible to eat a properly balanced and very varied diet as Dr Mosley recommends, and that is needed for health. For safety’s sake a full-blown elimination diet must be medically supervised.
Your first step is the detailed daily food and symptom diary for *at least* a week before you start, with everything weighed and measured (p.187). This will help you determine which food group or food type is potentially problematic and thus should be eliminated first.
Dr Mosley and co “don’t recommend removing too many foods at one time, so it might be helpful to do remove and repair in several stages” (p.190).
If you already avoid dairy you can continue to do so, but ensure you take whichever supplements your family doctor, dietician or pharmacist has recommended. If your issue is lactose intolerance you should be able to reintroduce traditional aged cheeses once your gut has rested. These are very low in lactose, yet loaded with gut-friendly probiotics.
HTH!