you're trying to cut 40-50 and are coming from a sedentary lifestyle, so you will fail if you try going all-out from the beginning with a super strict diet and body-building type of regiment.
before failing by attempting that, simply eat from a collection of these groups for each meal. for exercise, briskly walk 5 miles 5 days per week and do some sets of push ups and sit ups daily.
proteins: chicken, turkey, fish, eggs, tofu
fats: almonds, walnuts, low fat cheese, low fat mayo, avocado, olive oil, natural peanut butter (occasional)
veggies: anything and everything
fruits: green apples, watermelon, cantaloupe, blueberries
avoid: anything with enriched flour, anything processed, any simple carb, sucrose
only shop on the perimeter at the grocery store
once you've lost your first 25 lbs by doing the above, the diet can be relaxed a bit while you start incorporating cross-fit and core building exercises.