By far the best thing for your husband is for him to simply agree not to comment on anything at all related to the food you are or aren’t eating, or weight loss, or anything connected with this.
Do you think you can ask him to help you in this way? If he knows you are doing this course, you can say it’s been recommended and you just want to try this out for a while (i.e. not being “helped” by a partner).
Assuming he agrees to this, he might need gentle reminders every now and then.
If he refuses to go along with this at all, you will need to develop a private thought process along the lines of invalidating what he’s said, such as “that’s none of his business… what I eat is up to me… I can eat anything any time… I can eat that food later on in private.”