A common thing I see come up both ingame and online is how there isn't much of a penalty for dying--namely from starving to death, especially during the winter. Unless you're cranking up the respawn distance, I tend to agree. As nice as the HP boost is, I don't find myself that concerned about maximizing my nutrition, mostly since max HP is only really relevant in combat situations. I can get by just fine otherwise on nothing but grain if I wanted to.
It'd be nice if we got a benefit of some kind for fulfilling our different nutritional needs. Having your nutrition at a certain level will give your character a small buff. I'd say at 50% or higher, the buffs kick in. That way you would have some leniency as far as keeping up with your nutritional needs, especially when you sleep, but it'd still take some time to recover the buffs if you die.
For example (it doesn't necessarily have to be these levels):
Fruit: +5% movement speed -- your character has the energy to run faster
Vegetable: +10% health recovery -- you'll heal faster, both over time and with healing items
Grain: +10% mining/swinging speed -- your character has the energy to work faster
Protein: +10% attack/projectile damage -- with stronger muscles you can hit harder
Dairy: +15% reduced fall damage, +10% damage taken reduction -- with fortified bones, you're able to withstand more damage
You'll still receive the HP bonus for having maxed out nutrients. Perhaps there could even be a bonus to each area if you have all nutrients above 50%, to encourage a balanced diet.
Meanwhile, starving will work a little differently. Once your satiety reaches 0, instead of immediately taking damage all of your nutrients will begin to rapidly deplete--after all, your body is basically eating itself alive at this point! Once your nutrients run out, THEN you'll start to take damage.
Let me know what you guys think!