Slowing down while loops

Questions & Answers
1

Hello! I want to figure out how I can slow down the while loops. If you don’t understand what I am talking about (which you most likely don’t) I have a hunger variable. When that variable reaches 0, I want the health to go down at a constant speed. (For ex. 1 health decrease per second) If I regularly use the while loops, the health immediately goes down to 0. How would I make the while loops go down at a constant speed?

script for more info:

using System.Collections;
using System.Collections.Generic;
using UnityEngine.SceneManagement;
using UnityEngine;

public class money : MonoBehaviour {

	public int currentMoney = 100;
	public int currentApple = 0;
	public int hunger = 100;
	public int health = 100;

	void Start () {
		
	}
	

	void Update () {
		if (Input.GetKeyDown (KeyCode.B)) {
			SceneManager.LoadScene ("shop");
			DontDestroyOnLoad (transform.gameObject);
		}
	}
	void OnGUI() {
		GUI.Label(new Rect(25,400,Screen.width, Screen.height), "$" + currentMoney);
	}
	void BuyApple() {
		if (currentMoney >= 20) {
			currentApple += 1;
		}
	}
	void food() {
		if (hunger == 0) {
			//Here is where I want to put the while loop
		}
	}
}
2

Use Coroutines for background worker thread

    // inside the class...
	private int health = 10;
	private int hunger;

	void Start () {
		StartCoroutine(UpdateHealth());
	}

	private IEnumerator UpdateHealth() {
		while (health > 0) {
			yield return new WaitForSeconds(1);
			if (hunger == 0) {
				health--;
			}
		}
		// here do something where player dies of hunger :(
	}
3

Thanks for the answer, @LiloE! Previously, your answer has worked for me but I cannot use it for my new game.
Here is the script that I have used:

using System.Collections;
using System.Collections.Generic;
using UnityEngine.SceneManagement;
using UnityEngine;

using System.Collections;
using System.Collections.Generic;
using UnityEngine.SceneManagement;
using UnityEngine;

public class hungerchange : MonoBehaviour {
	public int hunger = 100;
	public int health = 100;

	void Start () {
		StartCoroutine (UpdateHealth ());
	}
	

	private IEnumerator UpdateHealth() {
		while (health > 0) {
			yield return new WaitForSeconds (1);
			if (hunger == 0) {
				health--;
			}
		}
		if (health == 0) {
			//SceneManager.LoadScene("Scene");
		}
	}
	public void OnGUI() {
		GUI.Label (new Rect(0, 0, Screen.width, Screen.height), "Health: " + health + "/100");
		GUI.Label (new Rect(0, 20, Screen.width, Screen.height), "Hunger: " + hunger + "/100");
	}
}

It justs stays on 100/100 for hunger and doesn’t decrease. Please help!