Sometimes when eating, my friends heart rate jumps from 75-80 to 120 or so. he's overweight and concerned, trying to reassure him. is this worrisome?

Maybe: It depends on his level of overweight. He should be professionally evaluated. How do you/he know that his heart rate jumps during eating? I would be more concerned about when he is exerting himself by walking or lifting. Without more information, all I can recommend is a complete physical and a visit to a health coach and/or nutritionist.