Episode 89 – Reasons Why You Could Be Feeling Fatigued

We will be focusing mostly on nutrition stuff, so we won’t spend much time talking about obvious stuff like sleep or medications. And we also won’t go deep on specific conditions such as Chronic Fatigue Syndrome.  

Iron deficiency 

  • Iron deficiency anaemia affects around 15% of the world‘s population. So if you experience fatigue, this is always good place to start looking.  
  • It’s simple to test just by getting a blood test. 
  • Addressing it could involve higher dietary iron intake, a transfusion or supplements. 

B12 Deficiency 

  • B12 deficiency is rarer but still relevant. Reportedly ~6% of people in the UK and US under the age of 60 have B12 deficiency. 
  • That number increases to 20% over the age of 60. 
  • Since B12 is found almost exclusively in animal based foods, this is even more relevant on plant based diets – so for my clientele specifically this is a big one I am checking  
  • Similarly this can be addressed through either increasing dietary intake, supplementing or B12 injections. 
  • Deficiency can be checked via a simple blood test  

Low calorie intake AND/OR low energy availability 

  • Low calorie intake in general can make you feel fatigued. Calories are literally units of energy, so this is unsurprising. 
  • Having a low-calorie intake in relation to your activity can lead to a state of low energy availability, which causes the body to down-regulate certain functions, which can make you feel fatigued. 

Being too lean in general 

  • Having an exceptionally low body fat percentage can lead to downregulations in functions, similar to the low-energy availability aspect.  
  • We see this in stage lean bodybuilders a lot, and it often does not reverse until quite some time post-show. 
  • Being ‘too lean’ is going to be individual for each and every person but probably falls in the range of <10% body fat for men and <20% bodyfat for women  

Thyroid stuff 

  • Although we are mostly sticking to nutrition, if you feel really fatigued it is worth getting your thyroid function checked. 
  • Both hypothyroidism and hyperthyroidism can cause fatigue. 

Vitamin D: 

  • Vitamin D deficiency has been linked with self-reported fatigue, although the link is not as strong as iron or b12 deficiency. 
  • The tricky thing with vitamin D is that we also get it from the sun, which can make it irrelevant at times e.g. what if not spending much time outside in the sun was a factor. 
  • To test this, there has been research that has involved supplementing vitamin D in those who are deficient, and it has found significant improvements in fatigue levels. 

Low intake of B-Vitamins in General: 

  • Although b12 deficiency is the most common one, most other vitamin B deficiencies result in fatigue. 
  • B vitamins can be found in a wide-range of foods. The simple way to avoid this is to consume a decent diet with a sufficient amount of a wide-variety of foods. This will sort itself out without much planning.  
  • People who avoid specific foods or food groups, or have less access to certain foods might be more likely to experience issues here. 
  • Either increasing intake, or supplementing B vitamins in general could help.  

So overall from a nutrition perspective, if you are feeling fatigued my first port of call would be: 

  • Get a blood test to check iron, B12, vitamin D and thyroid function  
  • Evaluate your energy availability especially if you are an athlete with a high training load  
  • If you are a lower body fat %, consider that this may be a factor 
  • And overall, I think it is also a good idea to check in with the overall quality of your diet

Relevant Links/ Resources

Iron deficiency stats

B12 deficiency stats

Studies mentioned

Vitamin D and Fatigue

B-Vitamins and Fatigue