The cat should do fine on IF. Put the food out for say 1-2hrs per day and donít have any out the rest of the time. A great cat food is Evo by Inova (http://www.onlynaturalpet.com/produc...od/204106.aspx
) grain free, high in protein and balanced n-3/n-6 fatty acids.
Diabetics SHOULD benefit from intermittent fasting but if things are done wrong serious complications, like death, can result! Try to get the Grandparents eating a paleo diet with only low GI veggies. If they are on insulin you will need their doctor in on this and things like blood sugar and drug dosages MUST be closely monitored to avoid serious problems. Simple nutritional changes and exercise could change everything for them. Start with that and then think about IF to further enhance their health.