Non-Fasted Cardio the True Key To Weight Loss? Study Shows Significant Increase in Total Energy Expenditure W/ Fed vs. Fasted Cardio - High Protein Adds to the Effect

Cardio & weight training are not mutually exclusive | learn more!
It's actually quite funny. A few days ago I wrote in a short blurb for the daily SuppVersity Classic Article that the "never-ending debate" about fasted cardio "has lost some of its momentum when the HIIT craze hit the fitness community" and today I get the following message from Päivi (thx!):

"This study totally contradicts my experience of fasted cardio. I've noticed that the best way for me to shred fat is to do fasted interval cardio, not fed one" (SuppVersity reader Päivi. March 24, 2014 | via Facebook).

"This study", in this case, refers to a soon-to-published paper from the University of Arkansas Päivi read about in a press release.
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Fasted Cardio & Beyond
In the corresponding experiment the researchers from the Human Performance Laboratory tested the differential effects of (A) fasted cardio, (B) cardio after the ingestion of a high (45%) protein meal, and (C) cardio after the ingestion of a low (15%) protein meal on the total energy expenditure of ten active (defined as burning between 500 kcal/wk and 2000 kcal/wk) women with normal body weight. And what they found is ... well, when you think about it, it's less amazing than it may appear.
Figure 1: Average metabolic rate (ml/kg/min) after the ingestion of high protein, low protein or no meal (fasted) and 40 min of cardio (5 min warm up, 30 min @60% VO2max, 5min cool down) in physically active young women (Binns. 2014)
If you take a closer look at the data in Figure 1 (and discard my analysis to the right), it may at first in fact look as if it was idiotic to do fasted cardio, if you could expend more energy if you had
  • 120g of delicious oatmeal, 20oz 2% milk and a slice of wheat bread with 9g of reduced-fat peanut  butter (low protein meal), or
  • 68g protein powder, 16oz of whole milk, 225g of Greek yogurt and 18g of reduced-fat peanut
    butter (high protein meal)
before the workout and still expend more energy. Now that's right: At first this may look idiotic, but if you take into account that these yummy breakfasts had slightly more than 800kcal it's highly questionable that the ~20% increase in total energy expenditure during the (presumably) 115min window that's illustrated in Figure 1 would compensate the additional energy intake of 800kcal; after all that's >50% of the lean ladies' daily basal energy requirements - a plus that would certainly not be compensated during the rest of the day.
If you want to lose weight forget about fasted or fed cardio and follow these 9 simple rules
Let's take a parting look at a pathetic increase in energy expenditure: If we do some additional math and sum up the ~6-7ml/kg/min "extra" energy expenditure for the whole 115min period (obviously that would be inappropriate because the difference is lower in the beginning), we find that the extra energy that may have looked like the solution to your "love handle problems" when you first read the abstract amounts to only ~120kcal (de facto we are probably dealing with max. 80kcal).

This leaves the ladies in the study at hand with an extra energy intake of 680kcal or 45% of their basal energy requirements. Needless to say that this was to increase energy expenditure during and after a workout is not necessarily conducive to your weight loss goals.
  • Binns, Ashley, Michelle Gray, and Ro Di Brezzo. "Thermic effect of food, exercise, and total energy expenditure in active females." Journal of Science and Medicine in Sport (2014).
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