AFAIK the Fast 800 Diet is the updated version of the 5:2 Diet. The Clever Guts Diet is about digestive health and general wellbeing not weight management.
What type of diet has been recommended by the prescribing doctor or registered dietician? It is important to find an eating plan that fits with the medical advice you have already been given.
Fatty liver is an inflammatory condition linked to metabolic syndrome. This would suggest eating more oily fish (up to four servings a week), more low sugar fruits and non starchy vegetables (*at least* five servings every day) in the full rainbow of bright and dark colours, whole unprocessed grains and pulses. This Mediterranean style of eating fits with all Dr Mosley’s programmes.
Have you starting keeping a detailed food and activity diary, with servings weighed and measured? Knowing where your diet is at present is key in moving forwards (or downwards on the scale).
HTH!