int availableHungerForRegen = hungerLevel - 17; // 18 or more hunger will regen
            float possibleRegenTicks = saturationLevel + availableHungerForRegen;
            return (float) Math.ceil(possibleRegenTicks / 1.5f);

public static float getEstimatedHealthRegenAmount(int foodLevel, float saturationLevel, float exhaustion) {
	float health = 0;
	while (foodLevel >= 20 && saturationLevel > 0) {
		if (exhaustion > 4) {
			exhaustion -= 4;
			saturationLevel = Math.max(saturationLevel - 1, 0);
		}
		health += saturationLevel / 6;
		exhaustion += saturationLevel;
	}
	while (foodLevel >= 18) {
		if (exhaustion > 4) {
			exhaustion -= 4;
			foodLevel -= 1;
			continue;
		}
		health += 1;
		exhaustion += 6;
	}
	return health;
}

      if (this.exhaustion > 4.0F) {
         this.exhaustion -= 4.0F;
         if (this.foodSaturationLevel > 0.0F) {
            this.foodSaturationLevel = Math.max(this.foodSaturationLevel - 1.0F, 0.0F);
         } else if (difficulty != Difficulty.PEACEFUL) {
            this.foodLevel = Math.max(this.foodLevel - 1, 0);
         }
      }

      boolean bl = player.world.getGameRules().getBoolean(GameRules.NATURAL_REGENERATION);
      if (bl && this.foodSaturationLevel > 0.0F && player.canFoodHeal() && this.foodLevel >= 20) {
         ++this.foodStarvationTimer;
         if (this.foodStarvationTimer >= 10) {
            float f = Math.min(this.foodSaturationLevel, 6.0F);
            player.heal(f / 6.0F);
            this.addExhaustion(f);
            this.foodStarvationTimer = 0;
         }
      } else if (bl && this.foodLevel >= 18 && player.canFoodHeal()) {
         ++this.foodStarvationTimer;
         if (this.foodStarvationTimer >= 80) {
            player.heal(1.0F);
            this.addExhaustion(6.0F);
            this.foodStarvationTimer = 0;
         }
      }

	/**
	 * Returns the expected regen amount, assuming starting from 0 exhaustion
	 * and without any external changes to exhaustion (jumping, sprinting, etc)
	 * during regen.
	 * TODO: It might be better to also take the current exhaustion level
	 * since that can change how much is healed if it starts above 2.
	 */
	public static float getExpectedHealthRegenAmount(int hungerLevel, float saturationLevel)
	{
		if (hungerLevel < 18)
			return 0.0f;
		if (hungerLevel < 20)
		{
			// every heal tick adds 6.0 exhaustion, which is equal to 1.5 saturation,
			// but it's not exactly equivalent, since the first heal tick will bring
			// you to 6.0 exhaustion, which will bring saturation down by 1
			// and exhaustion down by 4.0 on the next tick. The heal tick after that will
			// bring exhaustion to 8.0, though, which will take 2 saturation over the next
			// two ticks (and bring exhaustion back to 0.0).
			// So, basically, every 2 heal ticks you'll lose 3 saturation.
			//
			// It ends up looking like this (where the saturation is what you have when you start healing):
			// 9 sat = 6hp with 0exh left over
			// 8 sat = 6hp with 4exh left over
			// 7 sat = 5hp with 2exh left over
			// 6 sat = 4hp with 0exh left over
			// 5 sat = 4hp with 4exh left over
			// 4 sat = 3hp with 2exh left over
			// 3 sat = 2hp with 0exh left over
			// 2 sat = 2hp with 4exh left over
			// 1 sat = 1hp with 2exh left over
			float expectedHealthRegen = (float)Math.ceil(saturationLevel / 1.5f);
			float leftOverExhaustion = (saturationLevel % 3) * 2;
			int availableHungerForRegen = hungerLevel - 17; // 18 or more hunger will regen

			// TODO: everything below here could definitely be cleaned up
			if (leftOverExhaustion >= 4) {
				leftOverExhaustion -= 4;
				availableHungerForRegen -= 1;
			}
			if (availableHungerForRegen > 0) {
				boolean willLoseTwoHungerFromFirstRegen = leftOverExhaustion >= 2f;
				if (willLoseTwoHungerFromFirstRegen)
					expectedHealthRegen += 1;
				else
					expectedHealthRegen += (float)Math.ceil(availableHungerForRegen / 1.5f);
			}
			return expectedHealthRegen;
		}
		else
		{
			// this is harder, since the health/exhaustion added each
			// heal tick varies once saturation is below 6.
			// Saturation >= 6 works like the hungerLevel < 20 section above, though.

			// TODO
			return 0.0f;
		}
	}

// Calculate the final hunger and saturation
int foodHunger = modifiedFood.getHunger(heldItem, player);
float foodSaturationIncrement = modifiedFood.getSaturationIncrement(heldItem, player);

int newFoodValue = stats.getFoodLevel() + foodHunger;
float newSaturationValue = stats.getSaturationLevel() + foodSaturationIncrement;

float expectedHealthRegen = getExpectedHealthRegenAmount(newFoodValue, newSaturationValue);