https://phys.org/news/2018-06-fat-carb-combo-stronger-food.html

What makes this finding interesting, says Small, is that foods high in fat and carbohydrate do not exist in nature with only one exception: breast milk. This makes sense, said Small, since it is important for infants to learn to suckle in order to survive.

"In the modern food environment that is rife with processed foods high in fat and carbohydrate like donuts, French fries, chocolate bars, and potato chips, this reward potentiation may backfire to promote overeating and obesity," Small said.

                                                            
                                    
                                    Explore further: 

Foods combining fats and carbohydrates more rewarding than foods with just fats or carbs