Guys, he's on a server and said his friends aren't having this issue.
I'd check the slightly less obvious answers. Does your Modpack use Geoastrata? If so, any brown crystal things nearby?(they cause a saturation effect that makes you less hungry, and if used enough, makes it take a long time to get hungry again)
If not, uh... Not as many ideas up my sleeve here.
Honestly, though, this is basically the least worrysome issue one can have in Minecraft. "Oh dear me, I am not getting hungry at all despite running a jumping around like a child with ADHD, and even when I am my health is coming back just fine. How quaint."
OK, less silly things it could be; Ars Magicka 2 on your server? If so, it could be that you're higher into the Plant and Life Affinities then you realized, as these two effects can easily do this(with some downsides at higher depths). Plant Affinity can feed you in daylight, and Life Affinity will heal you like if you had full hunger, just slower then that.