You don't have to be a health professional to understand that your body was designed to be used. If you don't use it, it gets confused and certain parts begin to shut down. The longer they stay shut down the harder it is to get them working properly again, regardless of what kind of fuel you use. Working with your body requires communication. The problem most people have in controlling their weight is they communicate with their body in the wrong sequence. The right way to proceed is by putting activity ahead of diet, so your body can help you determine how much fuel it needs to do what you ask it to do.
We know our mind can control our body. We believe a well conditioned,
properly fueled body can help you control your mind
You are an Omnivore and that means you are an efficient food processing machine. If that weren't true we wouldn't be able to reduce all the complexity of food into a single number that gives us the total energy the body can extract from it---the Calorie. Your body has an Engine that coverts calories into energy. It is your Basal Metabolic Rate that determines how much fuel your body needs to do what you ask it to do. It might prefer certain calories over others and you'll be healthier in the long run if you provide it high quality fuel, but it will process almost anything you give it as long as you don't give it more than it can use.
If you give your body more calories than it requires it stores the excess as fat. It wants to burn calories to produce energy, not waste its time converting what it can't use into fat and then storing it for later use. Good nutrition is very important to your long term health, but it is not what determines how much you weigh. It's the balance between your Lifestyle and how much Activity you have that determines how much you can eat and control your weight.
When you eat whatever you want and expect your body to work it off you are working against it.You are working with your body when you help it understand how much energy it is going to need to produce before you ask it to the process the fuel. Then it can assist you in determining how much fuel it requires to meet your energy needs. It wants to keep its calorie burning engine running producing energy, not playing guessing games with you over how much energy you want it to produce.
"Fight or Flight" is a response...it's for emergencies. It's something your body does, not something it plans for or wants to do. It doesn't want big changes all at once. It wants to "adjust" which is why it sends you uncomfortable signals when you begin something new, but as you continue even intense physical activity gets easier. If you keep going your body looks forward to it. Stop and it misses it...the same is true of fuel.
Your body was designed by someone much smarter than you. You can't just start and stop your engine whenever you want and expect it to perform well. Work with your body by keeping your motor running so you can teach it what you want it to do and then it will help you determine how much and what type of fuel it needs to get the job done.