Well, a calorie is a calorie regardless of what it comes from...your body will find something to do with it but lets say in the case of high carb, high fat, low protein (because a the burger is a tiny amount of the food volume)...that reaction goes along the lines of developing insulin resistance, increased blood lipids and loss of LBM or broadly and generally speaking, exchanging lean mass for fat. When you throw in low fibre and high salt you've got impact on gut health/flora and blood pressure to consider. So, your weight can stay the same but you'll get doughy, pasty looking and your hair and nails will get brittle (indicators of micronutrient deficiency).