Sigh….I know! I know! It’s confusing. Every other week, a new diet approach. Keto. Vegan. Paleo. Here we go again. Bottom line is, there is no one diet fits all and part of what I do for you is give you the most up to date research available. Intermittent fasting is a new buzz phrase going around the internet health circles and to my surprise, there is no shortage of research surrounding this method of meal planning. It has definitely sparked curiosity amongst the science and health communities, particularly about its effects on obesity, insulin resistance, sleep cycles, and fat metabolism.
First, what exactly does intermittent fasting mean? Well, it’s what it sounds like….most commonly it involves a period of 2 days per week, every week, of no food whatsoever. However, some alternate days of fasting where every other day they eat and drink what they want and the opposite days they consume zero calories. And then there are some methods that specify time periods of each day where food is allowed and food is not. Usually you are allowed calorie-free fluids, but that’s it. The theory is that our body needs a “break” from food on a regular basis to produce health benefits. But what does the research actually say? These are the questions I’m going to attempt to answer.
1. Does it help with weight loss? This is really the million dollar question in my mind. I preach not to go more than 5-6 hours without eating because, after all, it actually slows your metabolism down and our bodies are designed to hoard calories when we don’t eat. Think of your body as if it were a car: food to the body is like gas is to a car. Without it, the body has no energy to move, which means the body is like a car that has run out of gas, parked on the side of the road….no fuel, nothing to burn. I’ve worked with so many clients who did not start losing weight until they started eating more often. Most drastic example I can think of is a woman who weighed more than 500 pounds and consumed only one meal per day that probably totaled to about 800 calories. She could not, for anything, lose weight. A month later, after eating double the calories, three meals a day with some snacks in between, she LOST weight. But that’s just my story, let’s look at some scientific studies.
In this small study of sixteen non-obese individuals, they lost an average of 2.5% of their starting weight after twenty-two days, so just three weeks, of alternate day fasting. However, they were HUNGRY. And that hunger never subsided. Do you think they kept at it after the study? A 5’5″ woman is technically overweight, but not obese, at 165 pounds….so if you lost four pounds in three weeks and you were starving, would you keep it at? Or find another diet, like the keto diet that is known to reduce hunger? It should be noted however that fat oxidation was increased during the study period, which means they were losing mostly fat mass and not muscle mass, this is a really good thing considering you want to keep your muscle mass when losing weight. These people did not maintain their losses, regrettably.
Here is a review highlighting several studies on alternate day fasting and comparing them to normal, calorie restricted diets (you know, the traditional method of weight loss you’ve probably tried a gazillion times.) They concluded that indeed, fasting is superior to producing weight loss and particularly, loss of fat mass. Pretty neat, huh? I’ve talked about the importance of this for preserving your metabolic rate in the past.
This last study compared individuals following an alternate day fast vs. combining it with exercise vs. exercise alone vs. a control group. These particular subjects were allowed a controlled, prepared meal that was provided for them around lunch time on the fast days. The meal was restricted to 450 calories and otherwise, calorie free beverages only. Feed days they could eat what they wanted, but they were given dietary counseling by a dietitian. Sounds pretty good, right? You may guess by now that the combo and alternate day fast group lost the most weight after twelve weeks at six and three kilograms (13.2 and 6.6 pounds), respectively. Again, most of the weight they lost was fat mass, not muscle. Awesome, right? It needs to be pointed out here though that they measured body fat using bio-impedance, which I’m not a fan of for accuracy….it’s the same kind you might use on your bathroom scale. Regardless, people are apparently losing the good kinda weight with intermittent fasting.
2. Does intermittent fasting improves insulin resistance and type 2 diabetes risk? I found lots about this one, too. The caution here if you have type 2 diabetes is that if you are taking medications that lower your blood sugar intentionally, many of the medications will not work without food OR they will work too well and cause hypoglycemia. So I’m going to begin this with an up front warning that what I’m about to say is not to be started without speaking to your doctor first if you are taking medications for diabetes. Okay?
In this pilot study (so just preliminary) on ten obese individuals, they experienced a reduction in their weight, body mass index, and fasting blood sugars after only two weeks. They fasted daily and only ate during a window of about six hours during mid-afternoon. Apparently they didn’t gorge themselves, because the article did say there was a spontaneous reduction in calorie intake measured from pictures they were required to take of all meals and food they consumed (talk about accountability!). At two weeks, this study really wasn’t long enough to say much, but six out of the ten said they would do it again.
In this study done on a small group twenty-four obese male war veterans, they did not see a significant change in fasting blood glucose or fasting lipids after six months of intermittent fasting (two nonconsecutive days a week.) Interestingly enough, their systolic blood pressures lowered and they did lose an average of twelve pounds…pretty good!
Lastly, in this review of several studies on the effects of intermittent fasting and insulin resistance, primarily reduction of type 2 diabetes risk, they concluded that the findings are showing promise for the use of alternate day fasting as an alternative to the traditional calorie restricted diets, but more research is required before solid conclusions can be reached. I perused some of their reference articles and the theme seems to be that the results are more profound in mice than humans so far. There was another review I thought gave some really good insight and from what I gather, if you are going to try intermittent fasting for the purposes of improving your blood sugars and/or insulin resistance, focus on fasting during the evening times specifically.
3. Does intermittent fasting help you sleep better? I bring this one up because we know that poor sleep habits lead to weight gain. So wouldn’t it be cool if there was a diet that could help you sleep better? I found two studies that looked at this. The first one was on eight volunteers who honored Ramadan, a religious period of fasting between dawn and sunset celebrated by the Islamic culture. They measured their melatonin levels via blood tests at baseline, during, and after. Unfortunately, they did not find any differences related to fasting. However, in this study, eight overweight individuals self reported better sleep when participating in time restricted fasting (food allowed <12 hours daily) for sixteen weeks. Subjective measurements are not usually as reliable, but these people obviously felt more refreshed waking up.
So what’s the verdict? Would you participate in fasting for a day or two per week or pick several hours each day to fast based on the evidence available? Seems like the information is promising, but the studies are small and preliminary. As for me, I’m not sure if I’m personally jumping on this bandwagon quite yet knowing there are other diets that are much easier to follow than this one.
P.S. If you’re looking for online support with like minded moms striving to live a healthier lifestyle, you may be interested in joining my free online support group here.
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Jillian McMullen, RDN, CSOWM, LDN