50 lbs in 7 months is totally doable. My husband has managed 30 in 4 and he is only primal when I feed him. The rest of the time he watches his calories, but all bets are off as far as the kind of food he eats. You probably can't be chowing down on primal breads and cakes, snacking on nuts or eating coconut oil by the spoonful, but a diet heavy on meat and veggies with enough fat and spices on the veggies to make them enjoyable should be OK.
CW-125, part calorie counting, part transition to primal
GW- Goals are no longer weight-related