In terms of waist (and weight) gain, a calorie is a calorie is a calorie. Calories that aren’t immediately used by the body for energy are either stored as fat or eliminated as waste. But that doesn’t mean your body treats all calories equally.For example, protein and fiber with high water content greatly affect satiety, or your feeling of fullness. Simple carbs have the least impact on satiety. Fat has a satiety effect similar to protein and fiber, which is why low-fat diets leave people hungry.QUIZ: Are You Eating for Beauty?Your body processes fat most efficiently. This means that you actually keep more of it, because your body doesn’t need to expend as many calories trying to store it. On the flip side, your body works hard to process protein, to make it flammable for your metabolic furnace.Contrary to popular belief, not all protein turns to muscle and not all fat goes to your hips. Everything you eat has the potential to be turned into fat. If your body does not use it for energy at the exact time it’s absorbed through your intestines. And, energy is energy.Here’s how you process the different nutrients…Simple sugars (like soda)Sugar is quickly absorbed and sent to the liver. The liver then tells your body to turn that sugar to fat if it can’t be used immediately for energy.MORE: Top 10 Sugar Foods (And Secret Sugar Foods)Complex carbohydrates (like whole grains)These take longer to digest, so there’s a slower release of the carbohydrates that have to be converted in your bowel to sugar, to become sugar in your bloodstream. This means that your digestive system isn’t stressed as much. Still, if your body can’t use this slower sugar when it’s released, it turns to fat.Protein (like meat)Your body breaks it down into small amino acids, which then go to the liver. If the liver can’t send them to your muscles (if you’re not exercising and don’t need them for maintenance or muscle growth), then yep, they’re converted to glucose. This then gets converted to fat if you can’t use it for energy.Fat (like funnel cake)This gets broken into smaller pieces of fat and gets absorbed as fat. Good fats (those in fish and nuts) decrease your body’s inflammatory response, while bad fats increase it. This inflammatory response is a contributing factor to obesity and its complications. If you’re exercising and have used all readily available carbs (sugar), your muscles can use fat for energy, which is an awesome way to slim down love handles.MORE: Are Low-Fat Foods Making You Fat?