Episode 129 – L-Carnitine and Fat Loss

Key Topics Covered

L-Carnitine and Fat Loss.

  • L-Carnitine is a naturally occurring amino acid that is proposed to help with a wide variety of functions.
  • A lot of people take it for the purpose of fat loss. In this podcast, we will explore how effective it is for that.


  • L-Carnitine helps with fat transportation in the body. It transports fatty acids to the mitochondria.
  • This is part of why people are interested. However, fat transportation does not necessarily directly translate to fat loss.

Research Outcomes

  • A systematic review from 2016 looking at 9 randomized controlled trials on the topic found an average of 1.3kg lost while taking L-Carnitine vs placebo.
  • A positive interpretation of that is that 1.3kg is better than zero. But some skepticism is worthwhile.

Reasons for Skepticism

  1. A study that had 36 women had 5 participants completely drop out due to nausea and diarrhea. That’s pretty relevant. Those symptoms would typically contribute to weight loss directly or indirectly due to reduced desire to eat. 
  2. Publication bias. Supplement studies always deserve some level of skepticism. 
  3. Absorption levels of L-Carnitine are really low. If it’s barely absorbed, how will it help?

Absorption Issues

  • >95% of the body’s carnitine is located within the muscle. 
  • Those who are plant-based have lower intakes of carnitine and carnitine precursors. They therefore also have lower baseline levels.
  • Research typically finds that oral supplementation of carnitine doesn’t significantly increase the body’s carnitine stores in omnivores.
    • For example, one study involved supplementing 2g per day for 12 weeks, and there was no difference in muscle stores in omnivores.
  • That same research DID find a 13% increase in muscle stores in those who were vegetarian though. 
  • The minimal change in absorption overall is a large portion why it makes sense to be skeptical about the effectiveness.

How to Increase Absorption

  • Firstly, the absorption issue is less of a factor in those who are plant-based. 
  • But there are some ways around it. 
  • One study used 2g of L-Carnitine alongside 80g of simple carbs, 2x per day (so double those total amounts). Participants were omnivores and their carnitine stores increased by 21%.
  • The issue here is that adding 160g of simple carbs to a diet to get a 21% increase in carnitine stores could be counterproductive.
  • Another way around this could be injecting carnitine instead of oral supplementation – but that’s outside of our area.


L-Carnitine is pretty rare to have a significant impact on fat loss. However, it may be more relevant if you are plant-based or taking a large amount of carbohydrates alongside it.

Relevant Blogs / Resources

Blog Posts

Studies Mentioned