From the feedback I’ve gotten on my series on Intermittent Fasting, I think this article will be of great interest to anyone looking to use IF’ing as a method for fat loss. I’d like to state that IF’ing is another modality to use to help improve body composition. People can still lose fat, while not IF’ing, I’m merely offering an alternative to the grind of eating 6 meals a day. Anyways, let’s see what fasting can offer us in terms of fat loss.
Martin Berkhan wrote an excellent review of a review which compared intermittent calorie restriction to calorie restriction in terms of effectiveness for weight loss. A review differs from a study, as it takes information from various studies and bundles it into one review.
What the study essentially concluded with was the following: “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.”
The intermittent calorie restriction that the studies used are a different protocols than I would use. In the studies, they allowed ad libitum feeding for 24 hour periods followed by 24 hour complete or partial food restriction. As you have learned from my series, the fasting times are set at 16 hours (females get a 14 hour fast). Nonetheless the results are going to be similar to the IF’ing protocol.
As noted in bold above, both CR and intermittent CR (I will refer to this as IF from here on out) resulted in fat loss. The most important part of this study was that the IF group was able to hold on to significantly more muscle mass than the CR group. How much do you ask? Well the CR group on average, lost weight at a ratio of 25:75, in terms of lean mass to fat mass. The IF group on average, lost weight at a ratio 10:90 respectively.
If that doesn’t make sense to you, let me give you an example. let’s say the average weight lost in the CR group was 15 pounds over a 4 month period. They would lose ~ 3.75 (.25X15) pounds of lean mass and ~ 11.25 (.75X15) pounds of fat mass. If the IF group lost the same amount of weight, they would lose ~ 1.5 (.1X15) pounds of lean mass and ~ 13.5 (.9X15) pounds of fat mass.
Again this study reviewed multiple studies. Some of these studies were done on individual who were exercising at the same time as they were in a calorie restriction, other studies were performed with diet only interventions. This is a pretty big flaw in the study. Only one study combined exercise and IF, multiple studies included exercise and IF. So theoretically, you might excpect the IF group to retain even more muscle than these studies concluded, with the inclusion of a resistance training program.
This is just hypothetical though. There are also issues of tracking fat loss in these studies. They used various tracking methods for different studies. Bioelectrical impedence (BIA) tends to be less accurate when compared to dual X-ray absoptiometry (DXA) or magnetic resonance imaging (MRI). Martin Berkhan sums this up quite well: ‘therein lies the problem; a larger percentage of the intermittent-fasting-based trials used BIA, while many of the CR-trials used DXA or MRI. If tracking methods differ between trials, it obviously skews the results. ‘
Since, I don’t have the study on hand, I haven’t been able to see the macronutrient breakdowns in any of these studies. Since the majority of studies rarely provide test subjects with adequate amounts of protein, lean mass is even harder to retain. If all these studies used only the daily recommended intake of protein, then the subjects were probably consuming less than half of what I would recommend. According to the FDA’s daily reference values, protein should make up ~ 10% of ones intake. I doubt even these studies used such a low intake, but it’s not hard for me believe they they used somewhere around 20%. This is still very, very low.
Nonetheless, a lot of information can be taken away from this review:
1. You do not need to worry about maintaining lean mass while IF’ing. Sure you may lose some lean mass, but as this review concluded, it’ll be a lot less than a regular CR diet.
2. IF and CR are both effective for losing weight! Again, if you like eating frequently, and are able to stick to multiple small meals on a daily basis, all the power to you. I’d rather have fewer large meals personally. The bread and butter with both of these diets is that you are in a negative energy balance.
3. If you are tracking fat loss, use the same tracking methods. I like to use skinfold calipers. In terms of calculating body fat, they aren’t very accurate. Skinfold calipers come in handy when used over months. The reason for this is that you can track the decreases in the measurements. If your measurements decrease by a total of 30 mm in a few months’ time, you know you have lost a significant amount of fat.
As for the reasoning behind why you are able to better retain muscle mass while losing weight… Well, we just don’t know everything quite yet. Could it have to do with the large GH spikes experienced during fasting? Could it have to do with increased catecholamines? Maybe it has something to do with insulin? Maybe a mixture of a bunch of these factors and others that we haven’t even identified yet.
I feel I’ve made it quite apparent in this series that IF’ing has some major benefits. If you are tired of eating 6 meals a day and seeing no results in your physique than maybe IF might be for you. If eating 6 small meals isn’t satiating enough, decreasing frequency will benefit you. Whether you eat three meals as part of an IF diet, or three meals as part of a regular calorie restricted diet is your choice.
I will tell you that it’s nice to not have to worry at all about food for the better part of your day. You get your meals in, and you’re all done. It’s also nice to leave the tupperware at home and just go out and enjoy yourself. As much as the media and supplement companies would like to have you believe that your body will wither away if you don’t eat every 3 hours, this just isn’t the case. I know I’ve made a valid point on IF’ing.
Until next time.