Body Fat and Your Nervous System – Stress, Sleep & Exercise.

nervous-system-body-fatNo worries…I’m not going to lecture you about the nervous system.

It would be incredibly boring and you’d probably fall asleep fast.

Instead I want to tell you about the relationship between stress and body fat, and show you how your nervous system plays a big role in burning or storing fat.

To make it simple, you only need to know there are 2 parts to the ANS (Autonomous Nervous System), and these are:

1) The SNS = Sympathetic Nervous System.
It raises your heart rate, releases cortisol, breaks down muscle tissue and drives blood away from the digestive system.

2) The PNS = Parasympathetic Nervous System.
It does the opposite from what the SNS does. It slows your heart rate, brings blood back to the digestive system, and repairs tissues. It also restores libido.


When we experience stress, this activates the SNS, which is linked to adrenalin.

When adrenalin is produced in response to stress, the body is in fight-or-flight mode, and it will burn sugar, not fat.

That’s why you’ll probably crave sugar when you’re stressed out. Sugar is the emergency fuel designed to save your life when your body perceives a threat.

Fat will only be burned when the PNS is dominant (or at least the nervous system is balanced).

Takeaway: being stressed fired your SNS and prevents the body from burning fat. In this situation, the body asks for immediate fuel, sugar, and will send a message to your brain that will produce a sugar craving (sugar can be sugary foods but also bread, pasta, any simple carbs).


The PNS does its job mainly at night before 2 am. Cortisol (the stress hormone) naturally starts to be released at 2am. We could say that from 10pm to 2am, PNS dominates and then from 2am to 6am, the SNS starts to be back. They both balance each other during an 8-hour night’s sleep.

If you go to bed late, your body won’t have enough time to repair tissues (very important if you have physical injuries or you have joint pain, etc.) or to burn fat. It will perceive you’re under stress even at night.

Takeaway: lack of sleep between 10pm and 2am will prevent the PNS from doing its wonderful job. Getting to bed by 10pm is important.


High-intensity exercise leads to fat loss only when the nervous system is balanced. If the SNS is dominant, the PNS is inhibited and fat loss becomes much more difficult, even when we do high-intensity exercise.

If stress is an issue in your life and your SNS is dominant, better suited exercise routines for you include yoga, tai chi or qi gong; any exercise that’s done slowly while breathing consciously. These will increase PNS activity to help balance your nervous system.

Takeaway: high-intensity exercise helps you lose fat only when the nervous system is balanced. If you’ve done such exercise and can’t see results, your SNS is probably dominant due to chronic stress; yoga or similar exercise routines would probably be good for you.

You see, I’ve not made it boring, right? 🙂

I wanted to share all this to show you that it’s necessary to keep our nervous system balanced, or we may never be able to burn enough fat, and we’ll keep wondering why the scale won’t budge even though we’re eating healthy and doing everything “right”.

This is #6 of these nutrition and weight loss series. Here are the other articles:
#1 – When Coffee Makes You Gain Weight (or Have High Blood Pressure)
#2 – Your scale is lying to you
#3 – Busy Woman Syndrome
#4 – Portion sizes matter more than calories
#5 – The innocent scapegoat (aka cholesterol)

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