Traditional diner French Toast can be over 300 calories per slice and rarely do you only eat one slice. Then add some syrup at 52 calories per teaspoon and you are looking at an 800 calorie breakfast, so the answer is yes eating restaurant French Toast on a regular basis can cause weight gain. That's why I recommend homemade low carb Air Fryer French Toast. At only 179 calories per slice with a sugar free syrup at only 15 calories per serving and some fresh fruit you can actually lose weight eating French Toast every day..imagine that!