This is a topic I am truly passionate about: all things metabolism. Without getting too science-nerdy, your body’s metabolism truly is amazing; there are thousands of processes happening in your body to digest the food you’ve eaten and turn it in to the energy you need to stay alive, every second of every day. Your metabolism also controls the efficiency of your body to burn fat and amongst other things, so it’s important we look after it.
It sounds almost the opposite of what we’ve been told through the media etc.
Let’s start with a concept called your Basal Metabolic Rate (or BMR or RMR). This is basically the amount of energy your body needs if you were lying down doing nothing all day (essentially the amount your body needs to keep all of its metabolic processes going). This amount is usually found through a DEXA (dual-energy x-ray absorptiometry) scan or BIA (Bioelectrical impedance analysis) scan, and can be used as a guide.
For our example, let’s say this amount is 1500 calories. So, your body needs this amount just to do its general everyday processes – not taking into account any activity or exercise. Let’s say you’ve heard the only way to lose fat and weight is to ‘eat less’ and decided to start a ‘diet’ (something I don’t advocate just by the way) and you’re eating ~1200 calories during the day. You’re trying to be ‘good’ and while you may be hungry still you know you can stick to it. Sure, in a few days or maybe a week, I’d assume you would have lost a little bit of weight. But this will most likely be just water weight (and from eating less than your body needs, I’ll explain this soon).
Let’s pretend you kept this ‘diet’ up for a few weeks. You’re training around 4-5 times a week, quite high intensity, eating around 1200 calories. Let me just sneak in here and add, your body and metabolism is adaptive and VERY smart and it does not like being in periods of stress. And for it, eating BELOW your BMR is stressful for it. And of course it is understandable why it’s stressful, your BMR is the basic energy (calories) you body wants just to survive.Okay, back to our example. Maybe you get to Friday night and go out for a few drinks with work friends. You think, ‘I’ll just have a little ‘cheat meal’’. No matter how ‘good’ you try to be on your ‘diet’, your body is screaming at you to have more calories. A cheat ‘meal’ turns into a ‘cheat night’ and the next thing you know you’ve had a few days where you’re eating whatever you want. Now this isn’t something to feel guilty about and you haven’t ‘failed’. Your body has been in a period of reduced calories and it is simply asking for more calories. The bad side about this is that you’ll more than likely put on weight with this period of ‘rebounding’.
Remember when I said our hypothetical BMR was 1500 calories. We’ve been eating ‘1200 calories’. And remember I said our metabolism is adaptive. Well. Now that we’ve been eating BELOW our BMR for a little while, our metabolism has actually lowered and now is ‘less efficient’. It’s now ~1300 calories. Now, if we wanted to ‘diet’ again. We’d have to eat less than what we were eating before to see any ‘weight loss’ (<1200 calories now). And so this vicious cycle continues.
Each time fewer calories are consumed, our metabolism goes ‘hold up lets slow our processes cause we are in a period of stress and threat’, and our BMR goes down. And do you think if our body senses it is threatened and stressed, it is going to want to be efficient at building muscle or efficient at burning fat? Definitely not! So how do we do this then? Even if your goal is fat loss or ESPECIALLY muscle gain, we need to be eating MORE than our BMR.
We also need to take into account any daily activity (i.e. lightly active job or sedentary) and exercise. Our metabolism is adaptive. Therefore, if we start by eating more than our BMR, our body adapts to using this amount of energy. Our body gets a signal that it is no longer in ‘stress-mode’ and can start doing the processes it’s designed to do. As always, this is for informative purposes and I recommend if you need specific advise then seeing a Sports Dietitian or Naturopath (for some support with hormones etc.) would be beneficial.