My personal opinion, you don't need to consult a nutritionist as such. Slimming World for example promotes cooking from scratch which makes your meals healthier.
Basically, don't use jars of sauces and make the sauce yourself. The jars tend to have oils and sugars in that you don't need and don't use when you actually make the sauce yourself.
And to me, the homemade things always taste better than the jars