Max "fat burning" (Review)

[WillBrink]

"fat burning" is the non science way of saying fat oxidation

What are the factors that leads to maximal fat oxidation? Here's an excellent review paper on that topic. Essential take home however is - and what lead to decades of bad fitness advice (e.g., "aerobics 'burns' more fat so that's what people should do to lose fat" and so forth...) - focusing on what leads to maximal fat oxidation does not translate into what's superior for fat loss per se. End of the day, energy flux is what it's all about. Or as Dr. Jose Antonio put it "Don't conflate acute FA with loss of fat mass."

Understanding the factors that effect maximal fat oxidation
Journal of the International Society of Sports Nutrition201815:3

Abstract

Lipids as a fuel source for energy supply during submaximal exercise originate from subcutaneous adipose tissue derived fatty acids (FA), intramuscular triacylglycerides (IMTG), cholesterol and dietary fat. These sources of fat contribute to fatty acid oxidation (FAox) in various ways. The regulation and utilization of FAs in a maximal capacity occur primarily at exercise intensities between 45 and 65% VO2max, is known as maximal fat oxidation (MFO), and is measured in g/min.

Fatty acid oxidation occurs during submaximal exercise intensities, but is also complimentary to carbohydrate oxidation (CHOox). Due to limitations within FA transport across the cell and mitochondrial membranes, FAox is limited at higher exercise intensities. The point at which FAox reaches maximum and begins to decline is referred to as the crossover point. Exercise intensities that exceed the crossover point (~65% VO2max) utilize CHO as the predominant fuel source for energy supply.

Training status, exercise intensity, exercise duration, sex differences, and nutrition have all been shown to affect cellular expression responsible for FAox rate. Each stimulus affects the process of FAox differently, resulting in specific adaptions that influence endurance exercise performance. Endurance training, specifically long duration (>2 h) facilitate adaptations that alter both the origin of FAs and FAox rate.

Additionally, the influence of sex and nutrition on FAox are discussed. Finally, the role of FAox in the improvement of performance during endurance training is discussed.

Full paper:

https://jissn.biomedcentral.com/arti...970-018-0207-1

[401Delta]

Good stuff.

The regulation and utilization of FAs in a maximal capacity occur primarily at exercise intensities between 45 and 65% VO2max, is known as maximal fat oxidation (MFO)...

...lead to decades of bad fitness advice (e.g., "aerobics 'burns' more fat so that's what people should do to lose fat" ...)

^^^This was taught verbatim straight out of the NASM textbook in the 90's.

...focusing on what leads to maximal fat oxidation does not translate into what's superior for fat loss...energy flux is what it's all about. Or as Dr. Jose Antonio put it "Don't conflate acute FA with loss of fat mass."

^^^But this key point was conveniently overlooked. Thanks for the link.

[WillBrink]

Good stuff.



^^^This was taught verbatim straight out of the NASM textbook in the 90's.

Which lead to a lot of crappy advice and excuse to do lazy LISS forever "cuz fat burning"

^^^But this key point was conveniently overlooked. Thanks for the link.

That's the money shot take home for sure.

[rectifryer]

Yes, any instantaneous loss of fat is maximized during 65% vo max but the actual higher magnitude of fat loss comes from replenishing glycogen stores and repairing the body from higher intensity activities. That doesn't mean both can't be used in harmony. If you train till 65% of your VO max is biking 20 miles in an hour then you've just made LISS your bitch for burning 700 cals/hour. It will take a lot of 80%+ work to get there though!

[DCSpartan]

Thanks for the truth bomb, Will.