Everyone is expected to have favorite foods and so you shouldn't feel that you cannot make a few requests.  For instance, you could ask your aunt to buy a whole grain breakfast cereal, fat-free milk or seasonal produce at the farm stand.  You could then be helpful by preparing interesting salads, grilling vegetables or baking healthy muffins for the entire family to try.  In the short run, you can easily improve your diet by reducing your meat portions and foregoing the junk-food snacks and sugary beverages. Your long-term goal should be to quietly set a good example and build on small changes over time.