Dietary restriction is an effective strategy for weight loss in obese individuals. The most common form of dietary restriction implemented is daily calorie restriction (CR), which involves reducing energy by 15-60% of usual caloric intake every day. Another form of dietary restriction employed is intermittent CR, which involves 24 h of ad libitum food consumption alternated with 24 h of complete or partial food restriction. Although both diets are effective for weight loss, it remains unknown whether one of these interventions produces superior changes in body weight and body composition when compared to the other. Accordingly, this review examines the effects of daily CR versus intermittent CR on weight loss, fat mass loss and lean mass retention in overweight and obese adults. Results reveal similar weight loss and fat mass loss with 3 to 12 weeks’ intermittent CR (4-8%, 11-16%, respectively) and daily CR (5-8%, 10-20%, respectively). In contrast, less fat free mass was lost in response to intermittent CR versus daily CR. These findings suggest that these diets are equally as effective in decreasing body weight and fat mass, although intermittent CR may be more effective for the retention of lean mass.
I thought this was an interesting review paper looking at a number of papers about human intermittent fasting in people (for which there are relatively few) vs. standard caloric restriction diets (for which there are many) to see which was more effective for weight loss. In the paper, what they describe as “intermittent CR” was another name for intermittent fasting (IF). The types studied were mostly alternate day-type fasting with either full or ~75% caloric restriction on fast days, rather than the time restricted feeding versions that I prefer.
What they described, but didn’t quantify in the summary above, was that dieters on more or less standard caloric restriction diets, 25% of their weight loss was lean tissue (i.e muscle), while in the IF groups the lean tissue loss was only about 10%. I wouldn’t hold those numbers as gospel truth at this point because the diets and fasting protocols were all a little different, as were the time periods over which the subjects were tested. I would expect combining both CR and IF with weight training would lessen, and I expect IF might completely eliminate muscle loss when dieting. It’s still unknown why IF appears better, but today makes 137 day on Fast-5 IF protocol and I’m now combining it with both heavy weight lifting and EMS, while still actively gaining muscle. It sure feels better than regular dieting, which I suspect has something to do with the adrenaline rush you get with it. I don’t know, there is a quite a bit of animal research on IF with human studies only recently being finished, so there is still a lot of uncertainty about what it can do in the long run and how it does it. However, as I’m on it longer and longer, it has gone from feeling “not that bad” and “not that hard,” to “this feels awesome!” I have taken some additional notes over the last few months on my thoughts with IF and weight training, compared to my initial 40 days. However, I don’t want to write them up until I surpass Gandhi’s record who fasted a total of 140 days over his lifetime. So just four more days to go on that, and it’s all too easy. Gandhi never did more than 21 days in a row, and apparently he did complete fasts rather than IF, but that’s neither healthy nor sustainable, nor do I think he could squat very much. In fact in the move the movie I saw, he had trouble walking afterwards.
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Chad Reilly is a Physical Therapist, obtaining his Master’s in Physical Therapy from Northern Arizona University. He graduated Summa Cum Laude with a B.S. Exercise Science also from NAU. He is a Certified Strength and Conditioning Specialist, and holds a USA Weightlifting Club Coach Certification as well as a NASM Personal Training Certificate. Chad completed Yoga Teacher Training at Sampoorna Yoga in Goa, India.