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TitanCT 01-31-2012 03:30 PM

Fed vs. Fasted Cardio
Advanced Muscle Science: Fed vs Fasted Cardio

Fed vs Fasted Cardio
Although the following research did not measure lean body mass, I'm sure those of you who practice intermittent fasting will appreciate this news.

A new study out of Tunisia looked at aerobic trained males and compared fat loss as well as total bodyweight between the two groups. What they found was interesting and for me unexpected. The fasted group lost slightly less total bodyweight. But at the same time lost significantly more fat (6.2%). This suggests they also had a greater retention of lean body mass. Unfortunately I'm unable to currently access this full text so many questions are left unanswered. However it still appears to be excellent news for anyone on the fasted cardio band wagon.


Effects of fed- versus fasted-state aerobic training during ramadan on body composition and some metabolic parameters in physically active men.

Trabelsi K, et al. Show all
Int J Sport Nutr Exerc Metab. 2012 Feb;22(1):11-8.
Laboratory of Pharmacology, University of Sfax, Sfax, Tunisia.

Abstract The aim of this study was to evaluate the effects of aerobic training in a fasted versus a fed state during Ramadan on body composition and metabolic parameters in physically active men. Nineteen men were allocated to 2 groups: 10 practicing aerobic training in a fasted state (FAST) and 9 training in an acutely fed state (FED) during Ramadan. All subjects visited the laboratory for a total of 4 sessions on the following occasions: 3 days before Ramadan (Bef-R), the 15th day of Ramadan; the 29th day of Ramadan (End-R), and 21 days after Ramadan. During each session, subjects underwent anthropometric measurement, completed a dietary questionnaire, and provided fasting blood and urine samples. Body weight decreased in FAST and FED by 1.9% (p < .001) and 2.6% (p = .046), respectively. Body fat percentage decreased only in FAST by 6.2% (p = .016). FAST experienced an increase in the following parameters from Bef-R to End-R: urine specific gravity (0.64%, p = .012), urea (8.7%, p < .001), creatinine (7.5%, p < .001), uric acid (12.7%, p < .001), sodium (1.9%, p = .003), chloride (2.6%, p < .001), and high-density lipoprotein cholesterol (27.3%, p < .001). Of these parameters, only creatinine increased (5.8%, p = .004) in FED. Creatinine clearance values of FAST decreased by 8.9% (p < .001) and by 7.6% in FED (p = .01) from Bef-R to End-R. The authors conclude that aerobic training in a fasted state lowers body weight and body fat percentage. In contrast, fed aerobic training decreases only body weight. In addition, Ramadan fasting induced change in some metabolic parameters in FAST, but these changes were absent in FED.

5kgLifter 01-31-2012 03:54 PM

The key point in the study is "aerobic trained males", people that were already aerobically well trained and would predominantly burn fat for fuel whereas a non-aerobically trained person, a newcomer or just someone that has not got as much of an aerobic base, may not use fat as the main fuel source...according to stuff I've read, doesn't mean it's the case though, just thought I'd highlight the point.

It's also well-known that the more bodyfat a person has the more the body will tap into the fat for fuel whereas those with leaner frames tend to burn less fat purely becuase they have less fat at their disposal which is why it is recommended that they don't train fasted.

Neither of these points may contradict each other since we don't know how lean the people in the study were and a decrease of 6% bodyfat would indicate there was a substantial amount of room for fat burn unlike in a bodybuilder with only 10% to begin with.

Chillen 01-31-2012 07:40 PM

I have tried both, fasted and fed at different points in my personal goals. In both starting points, the body fat percentage aspect were the same, both were within a calorie restriction; the only difference was total body weight.

Each were done for a 4 week period, under virtually the same length (of cardio session), frequency during the week, and circumstances, with the exception one was fasted and the other fed (about an hour before).

I lost more total body fat/less overall weight, and reacted marginally stronger in fasted cardio state as compared to BF loss in the fed state. Overall body weight nor the amount of fat I was carrying had no effect on the results.

Interestedly, however, I have also learned I do not need cardio to "assist" in fat loss (though I still do it, as its part of my health composite of goals).

By manipulating certain aspect of intensity in weight training, and adjusting macros, and I can get "like results" as compared to fasted cardio, and basically eat anytime I want without regard to being in a fasted state or when I eat. For example: Manipulating Time between sets in a pyramid up where time between sets progressively gets lowered with each subsequent set, where the last set ends up 20 to 30 sec rest, and the weight being used is pyramided up where the weight drops for each set but is progressively increased each workout session. In addition, the starting time between sets also drops one tier the next WO session. Here we have intensity increase and weight progression at the same time. Likewise, carbohydrates are reduced, and glucose storage gets effected, and I get good results with sort of set up briefly explained in losing BF over a short range of time in a calorie restriction environment.

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