Although there are some debated topics in exercise science, most are agreed upon and straight forward. Nutritional science does not provide much black and white answers to the endless questions we have. When obtaining my certification in this area I was greeted with a lot of gray area as professors gave presentations that were sometimes contraindicated to the lecture in the next room. So, the best I can offer to clear up misconceptions for you are areas where the current science has debunked prior theories or at least it is mostly agreed upon.
1. Eating fat makes you fat
A simple rewording of this phrase starts to clear up this idea. Eating the macro-nutrient energy source of fat does not directly add to the visceral or subcutaneous layers of body fat. We can thank the scientist Ancel Keys with a one track agenda in the 1950's with this myth that we are still struggling to let go of. Sadly even decades after the low fat diet craze of the 1980's we are still being taught that all types of fat are dangerous to consume leading to health problems and weight gain. My certification was obtained in 2004 and this was the underlying message still at that time. Present time messages are steering us away from fat as the problem and pointing the evil finger to carbohydrates. But not all carbs are bad either. Aim for high quality saturated fat (organic animal fat, coconut oil) and monounsaturated fat (avocado, olive, nut oils) as opposed to highly processed toxic fat and oil. "White" processed carbs such as sugars and grains should take a back seat...way back...if at all consumed to whole food sources of vegetables, (root veggies have more than carbs than cruciferous types) fruit, nuts, and whole grains.
Summary: eating healthy types of fat is necessary and beneficial. Same goes for carbs and protein. You can even safely eat a diet higher in fat as long as the carbohydrates aren't being overly consumed at the same time.
2. Less calories in + more calories out = weight loss
This is a tricky one. It's pretty logical and easy to say burn more calories than you consume and you'll lose weight. It does not take into account that our body freaks out with the fear that it will not be fed the energy it needs for all its functions after we start giving it a deficit for too long. Possibly registering the internal thought of "holy crap they're letting me starve!" Causes the body to hold onto any extra calories it does get to prevent perceived starvation. Sometimes even slowing down the metabolism to assist.
Summary: Eat the right types and amount of food along with moving your body for weight loss benefits.
3. All calories are created equal.
As mentioned in point one, the quality of food is pretty darn important. Your body may or may not react to organic vs. conventional, toxic trans fat vs. fresh high quality fat, simple processed sugar vs. naturally sourced in the moment but, the effects on long term health aren't negligible. Choosing the best quality that you can afford and making it a priority can literally add years to your life. Think of it as preventative medicine. This list of the dirty dozen and clean 15 tell what foods you should opt for organically.
Summary: Always chose the highest quality available for your budget.
4. Breakfast is the most important meal of the day
Well....it can be but it depends on your goals, activities, and current dietary lifestyle. If you chose to practice intermittent fasting for health reasons, a popular technique is the 16 hr fast followed by an 8 hour eating window. One of the easiest ways to accomplish this is to eat later in the morning counting the sleeping window into that fast. For example, eating at 6 pm and not eating again until 10 am the next day. If you are exercising in the morning at a low intensity with a duration of less than 2 hours, this method could still be used. However, if the morning workout is a high intensity one where you are tapping into the glucose stores more readily, that small morning meal may indeed be pertinent to the outcome of the quality of the training session.
Summary: Eat a balanced meal if morning workout is intense, or if you are listening to your body hunger levels while not practicing intermittent fasting.
5. To make progress you have to track your food
Again, yes and no. It can be helpful at first for a few weeks to a month to see what you have been stuffing your gullet with especially if you eat mindlessly...which is pretty common, But, the end goal should be to eat mindfully listening to your body for ques on when you are actually hungry. And learn to stop eating before you are too full. With practice eating without distractions all the time, we can start to learn not only when the body needs food but, what it is really craving nutritionally.
Summary: Listen to what your body is telling you, not your emotions.