In one of my previous blogs I was talking about the 3 diets that make sense from a scientific standpoint. I also did a mini-experiment on myself trying to use all 3 approaches (low-calorie, low-carb and intermittent fasting) to lose 15 pounds in 15 days. It worked then, but being a scientist, I am very curious about the potential of each of these approaches and how much they contribute to weight loss on their own.
I had a chance to try intermittent fasting without restricting the amount of calories or carbohydrates I consumed. This experiment was also 15 days long and now we can see the difference between intermittent fasting and the 3 approaches combined (which is the gist of Dr.Sam's nutritional approach).
I started at almost the same weight as I was at when I did my 15-day experiment (207.5 lb vs. 202.8 in the original study). I restricted my meal intake to a very short feeding window of approximately 2-4 hours every day. I must say that this part worked amazingly as I am naturally too busy to have my breakfast and lunch. In the evenings I would have an amazingly rich meal without any restrictions and charted my weight daily. Now, I am happy to show the outcomes to you (see Fig.1).
As you can see, there were some weight fluctuations over the course of these 15 days, but my weight remained the same (207.9 vs. 207.5 at the baseline), which is very different from what I managed to achieve when I tried my approach (Dr.Sam's on the chart) before, while I kept all other variables (nutrition, sleep and the subject - myself) the same.
I must say, that I am not surprised at all. I still believe in intermittent fasting (IF), but I cannot fathom the concept of burning fat while consuming excessive amounts of calories. I know that intermittent fasting is the mainstream approach these days and I do believe that this approach is effective for those want to build muscle while burning fat - it does give you a fantastic anabolic boost and helps building muscle and burn fat, but at the same time, if you consume too much food, and accordingly - too many calories - your body has to do something with this energy and it naturally stores it as fat.
Again, I'm a scientist and I tried to find a good clinical trial to see if there is any good research evidence to support IF vs. IF with calorie restriction. While it was difficult to find a study that would match my research question, I was able to find one study that compared intermittent calorie restriction to continuous calorie restriction . The study was published in the International Journal of Obesity in 2011 by Harvie and coauthors. It focused on two groups of individuals, one of which (n=53) received continuous energy restriction (25%), whereas the other group's (n=54) caloric intake was reduced by 75% twice weekly. I've summarized the main outcomes of the study in Fig.2.
The study was well-designed from the scientific stand point, subjects were randomised and groups were similar to each other. I have some issues with the design of the caloric intake sessions, specifically, I'm not sure why they had IF days only twice a week - it defies the whole purpose of the IF approach and, in my opinion, undermines the findings.
Nevertheless, this is a scientific evidence and I think we should use it to advance our understanding of the effects of intermittent fasting on weight loss, though in this case in quite abridged format. The study showed that both intermittent and continuous energy restriction leads to weight loss. The intermittent caloric restriction yielded slightly better results, but the difference was not statistically significant, which in a sample of over 100 people is quite compelling. In a nutshell, the study showed that caloric restriction (CR) works and that IF is a questionable addition to caloric restriction. Given the study design shortcomings, I would envision some future studies where they have their subjects use intermittent fasting and compare it to energy restriction, ideally, three groups - one would undergo IF, another - CR and the third one would have a combination of IF and CR. This kind of research would provide us with the most definitive answer to our question in the future (If you come across a study like that, please forward it to me).
For now, we can still rely on our common sense and on the limited data available. I still believe that intermittent fasting as an excellent approach to body transformation as it gives us a powerful anabolic boost and should help maintaining muscle mass while losing fat - an ideal scenario for body transformation. Still, if we focus on weight loss, rather than on body building, I cannot recommend doing IF alone without restricting your calories. I will keep searching and will keep you posted on my findings as usual.
1. Harvie MN, Pegington M, Mattson MP, Frystyk J, Dillon B, Evans G, Cuzick J, Jebb SA, Martin B, Cutler RG et al: The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. International journal of obesity (2005) 2011, 35(5):714-727.