Do Metabolic Trackers Really Work?

Mickie17

Do Metabolic Trackers Really Work?
If so, which ones? And are there any affordable apps to use with them?
Have been researching Lumen. $$$$$$$$$

yirara

These seem to be mostly quack to be honest. Lumen says they're using RER and a mysterious algorythm to determine whether your energy usage comes from fatty acid or glycogen. RER is the ratio of oxygen inhaled vs CO2 exhaled. It can be easily messed up, for example by hyperventilation or underbreathing. This machine should to start with use RQ instead of RER. And does it matter whether your body uses glycogen or fatty acids for energy? I don't think it does as energy is constantly in flux in our bodies. Glycogen stores empty? Fill them up. Full? then store excess calories as fat.

Here's an interesting paper on two people that can't properly access fatty acids as energy due to a medical condition: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3565639/
Yet they were able to lose weight. The complication here was not not losing weight but going into hypoglycemia. Thus what Lumen claims, that you can only lose weight when you use fatty acids as energy source is just wrong.

It might be useful for people that train for long distance running/cycling/skating/whatever and want to be able to make better use of fatty acids as energy source during their training. After all, the amount of glycogen in the body is limited while fatty acids are a very huge energy source and can keep them going for longer without the need of using gels. But I guess that you'd then need to use this during your training and not in the morning or whatever.