How does a poor diet with unhealthy habits affect the heart to work harder? What are the effects?

Well eating unhealthy, junk food, etc could coast ur heart to stop or have a heart attack

it Takes Less Energy to Digest Junk Food

In fact, eating a high-protein diet may cause your body to burn up to 100 more calories per day (8, 9, 10) ... Processed junk food requires less energy from your body to digest because it's high in refined ingredients.