Turkey ince is no where near as fattening as beef mince, as it contains very little fat, same as chicken.
Its worth keeping some red meat in your diet, everything in moderation afterall, just try to buy very lean cuts, you can get lean beef mince. But I wouldnt opt for lasagna unless you heavily modify it as the cheese sauce and everything make a very fatty meal. But Spag bol is fine, be sure to drain for any excess fat before you add the tomato sause and try to make your own sause using tinned tomatoes as jar sauses contain a lot of extra crap and thickeners and sometimes fat so arnt always very low fat!