Today, we have a fresh off the press study looking into ‘Intermittent Energy Restriction (IER)’ and its ability to shred body fat, preserve muscle mass and resting metabolic rate (RMR) for more effective and efficient body transformations.
Before heading any further, IER is essentially a form of calorie or carb cycling. You may have heard online or through ‘gym chat’ regarding how promising it is, however all of this is very much anecdotal with a snippet of mechanistic based studies…nothing concrete.
Until now…Campbell et al (2020) looked at the effect of a 5 day ‘low’ calorie phase followed by a 2 day ‘refeed’ and its impact on body composition when compared to a standard continuous diet (in already lean people).
To make thins super fair, both dieting groups has the same 25% weekly calorie deficit for 7 weeks and performed the same supervised 4 day (upper/lower) training split.
– Refeed = 5 days at 35% calorie deficit followed by 2 days at maintenance (i.e. not a mega surplus).
– Continuous = 7 days per week at a 25% calorie deficit.
The perfect result would be: Refeeds = greater fat loss, muscle mass retention and no drop in RMR.
When we look at the average, muscle mass retention/gain was greater in the refeed group, as was fat loss and maintenance of RMR – awesome! But not so fast…
When we look at the individual data points for muscle mass (Fat Free Mass – see image), you can clearly see that some people responded to refeeds where some people didn’t. Meaning that on overall average, refeeds were better, but not for everyone.
RMR changes after 7 weeks were -38kcal in the refeed group and -78kcal in the continuous group…i.e. no real work difference (imo).
Fat loss was -2.8kg and -2.3kg in refeed and continuous group respectively. Again, real world difference isn’t huge after 7 weeks.
From my own perspective and experience applying carb cycling, the main difference is the psychological component – simply knowing that you can eat at calorie maintenance on the weekend after 5 days of slightly harder dieting makes the whole process far easier and sustainable when compared a long haul continuous and monotonous dieting phase.
IMO, this is where the main gain in calorie cycling comes from; the psychological, not the physiological…for most anyways, some will still get sweet gains.
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