how do I stop food item from increasing hunger incorrectly?

I'm trying to make a survival game and so far I'm on the food system part of it. I made an apple that increases your hunger by 5 but every time I use it, It keeps going to 105 no matter what percentage the hunger is at, then if you keep eating it, it just increases the hunger further.

Hunger decrease script

local player = game.Players.LocalPlayer
local character = player.Character
local humanoid = character:WaitForChild('Humanoid')

local hunger = script.Parent.HungerBar

while wait(.5) do
    if humanoid.Health > 0 then
        if hunger.Value > 0 then
            hunger.Value = hunger.Value - 1
        else
            humanoid:TakeDamage(5)
        end

        local fullHunger = 1
        local currHunger = hunger.Value / 100
    else
        hunger.Value = 100
    end
end

My best guess was to put something like "If value >= 100 then value = 100" (same with 0) but I didn't know where to put it, so it only broke the script.

Tool Script

local tool = script.Parent



function onEquip()
    tool.Equip:Play()
end

function onActivate()
    wait()
    local player = game.Players:GetPlayerFromCharacter(script.Parent.Parent).PlayerGui.Bars
    local hunger = player.Hunger.HungerBar
    local thirst = player.Thirst.ThirstBar
    tool.Apple_Bite:Play()
    hunger.Value = hunger.Value + 5
    tool:Destroy()
end

tool.Activated:Connect(onActivate)

tool.Equipped:Connect(onEquip)

Is there something I'm missing on the tool script? Some sort of changed event like for the gui text to record the value?