You're looking at the issue through a straw here, not seeing the whole picture. Energy expenditure is not limited to the workout itself. Depending on what you're actually doing during that 30 or 60 minutes, you might burn a significant amount of calories long after the workout itself is over. If you spend 15 minutes doing a hard anaerobic sprint workout and you spend 1 hour jogging at a slow pace, there's a good chance that you burned more calories while jogging. However, when you're done jogging, you're basically done burning energy. When you're done sprinting, your body has only just begun to burn calories, and your metabolism will be elevated for a day or two afterward as your body replenishes it's glycogen stores. Again, that's only one part of the issue. Going 8 or more hours without eating (sleep) is already bad enough from the perspective of muscle catabolism, but skipping breakfast and going 12 or more hours without anything is going to signal your body to slow down its metabolism, decrease lipolysis, and increase muscle catabolism. When you break the fast you halt your muscle breakdown and raise your metabolism back up from the reduced rate brought on by sleep. Not to mention, the earlier your consume your calories, the more likely they are to be burned. Unless you eat one ginormous breakfast, it's pretty much a given that everything you eat is going to be burned up by the end of the day. If you skip breakfast and pack your calories into the latter part of your day, you're more likely to store them as fat, because by the time you go to sleep you've got lots of carbs, fats, and proteins floating around in your system and a zero activity level. Not to mention the obvious problem with skipping breakfast - you won't have any energy for the first part of your day. Newlearner The carbs in fruit are monosaccharides, simple sugars. Regardless, fructose is great for you, and is very low GI. Carbohydrates are more complicated than "simple" and "complex", as Garrett touched on already.