Posted on October 18, 2018 by Emily Forbes

Your trainer has told you to get a good nights sleep. You’ve read it in a magazine too. But why do people say this? Is lack of sleep really ruining your diet? Not directly, but quite possibly, yes. I’m reflecting on this because this is a cycle I have just been through. I’m here to tell you how lack of sleep can ruin even the best efforts and why you should get those zzz’s in.

Lack of sleep truth:

  • When you are tired you aren’t able to train as efficiently or even have the energy to train at all. Two weeks ago I went to a vinyasa yoga class and spent the hour in savasana (for those that don’t know, I basically lay down for an hour. But it did help bring up my energy). I recently had to make time in my diary which meant I had to cut training sessions. The only pro was that I got more time. What I lost was my downtime and head-clearing space which helps keep my stress low and my life more manageable. Exercise also helps you sleep better so was I sabotaging that even more without training.
  • The combination of sweet and fatty foods (cue cake and chocolate), whilst not directly addictive, do trigger hedonistic areas of the brain (serotonin/dopamine) which make us feel good.  When we are feeling tired and low, it is these feelings that we want to replicate and have us reaching for the cookie jar.
  • Tie in the above with a complete lack of willpower and you can see why diet disaster is just on the horizon. Willpower takes energy. If you are depleted you are going to find it ten times more difficult to say no to things. Along with additional thoughts that “I deserve it” or “I need sugar for energy”.
  • Are you also mentally tired as well as physically tired? Are you doing too much? I find being mentally tired much harder to recover from and this can leave you feeling super drained. For me, I was studying/revising, working and still trying to fit in my daily life. Enough sleep doesn’t fix the problem, you need a complete break from the situation. I knew mine was only temporary but perhaps you have a  high demand job/life where the pressure is constant. This might be where alcohol and comfort food starts making an appearance too.
  • Lack of sleep can also affect us physiologically. Our hunger hormone ghrelin can increase and our appetite inhibiting hormone, leptin can decrease. Meaning we can potentially feel more hungry and over-eat more easily.


So the answer is, yes, lack of sleep could be ruining your diet. It happened to me. I could see it happening to me. And I literally felt powerless. The cake was there and I couldn’t say no. But as I said, I knew it was temporary. But this week I am back in control. I’ve cleared the source of the stress and I’ve got my mojo back.  I’ve done a 1 day fast (200kcals), trained numerous times and not snoozed despite the alarm going off at 4:30 am. I can speak from a place of honesty and experience when I say get some rest if you want to help your diet/training.