by Barbara Berkeley, MD
You may be interested in a study that was published by JAMA Network last month and drew some positive conclusions about Intermittent Fasting. Intermittent Fasting remains a topic of interest for those who want to lose weight and for those who treat those people. There are a few important questions. First: does it work? Second: Is it healthy? Third: Is it sustainable as a long term intervention?
The JAMA article, which you can read HERE, is a deeper dive into 11 meta-analyses of IF for weight loss. A meta-analysis is a sort of summary study which groups together a number of individual studies (called "randomized controlled trials") and is able to draw larger conclusions by comparing them. An umbrella study goes to the next level and looks at multiple meta-analyses. So in this case, 130 separate studies were reviewed. In addition, the umbrella study re-examined the data and re-calculated the strength of the evidence of all the smaller studies. The idea was to present conclusions that were consistent and reliable.
There are many ways to fast or to limit food intermittently. For the purposes of these studies, four techniques were examined:
ADF: Alternate Day Fasting. The person fasts completely every other day. On the non fasting day, he eats whatever he likes.
MADF: Modified Alternate Day Fasting. The person eats 600 calories or less 3 to 5 days of each week, and eats whatever she likes on non fasting days.
5:2: Five/Two. The person eats 600 calories or less on two days each week. The days may be consecutive or non consecutive. He eats whatever he likes on non fasting days.
TRE: Time Restricted Eating. The person fasts for some period each day. In my experience this is usually 12 to 16 hours.
So. Did these techniques work? Results showed that intermittent fasting may be beneficial for obese and overweight people. But the data on weight loss was---for me----underwhelming. Only two types of IF (MADF and 5:2) were associated with statistically significant weight loss of greater than 5% and the range of weight loss seen in the studies was 0-10%. It was also noted that weight loss only occurred early on and that by six months weight loss had stopped and people had plateaued. While 5% may represent statistically significant weight loss, it does not make my personal definition of clinically significant weight loss. In my weight loss practice I liked to achieve a 20% weight reduction whenever possible. Thus a 180 pound woman who once weighed 130 would lose 36 pounds and would weight 144. The 20% loss would not achieve her original weight, but it would be significant. On the other hand a loss of 9 pounds (5%), for a new weight of 171, (at least for me) would not.
The umbrella study also pointed to metabolic benefits of IF:
"We identified 104 associations and found significant beneficial outcomes associated with IF on BMI, body weight, fat mass, LDL-C, total cholesterol, triglycerides, fasting plasma glucose, fasting insulin, HOMA-IR, and systolic and diastolic blood pressure, mostly in adults with overweight or obesity".
So I think we can conclude that fasting techniques are an interesting way to potentially improve the markers we associate with inflammation and modern disease. Evidence for strong effectiveness as weight loss tool? Not so much.
But wait a minute? What about IF for maintenance? We are now over 30 years into the obesity epidemic and there is still so little written about how to keep weight from returning. I know this is a tremendous frustration for those of you who have lost weight many times only to see it return. Unfortunately, maintenance is weight loss's poor cousin. Weight loss is dramatic and sexy. Maintenance is difficult and mundane. And even the research community seems to see it that way. So let's continue to make our own way and generate our own observations.
And here we will enter the realm of pure opinion. Anecdotally, I find that some type of consistent intermittent fasting---modified to fit one's own body and lifestyle---is a significant maintenance tool. Just because the science community has given definitions and titles to types of IF, it doesn't mean that these are the only ways to roll. In my own personal battles to stay below scream weight, I have found that skipping dinner in favor of having something minimal like a protein bar or a yogurt is a great help if done at least two nights a week. On those nights, I also exercise. For me, that's either dancing or tennis. I will schedule a class or a match in the evening around 6:30. I'll eat lunch and maybe a little something at 3 or 4 on that day. I'll exercise hard, come home, and either just hydrate or have the aforementioned yogurt or bar. This technique does not fit any of the definitions of IF listed above. But it works very well for me. And if my weight ever starts creeping up, I try to do the same thing a couple of nights in a row. Additionally, I always try to stop eating early and get at least 12 hours without eating again. I like to be done with food by 8 and have my morning coffee at 8 the next day. During those 12 hours, my body is being asked to release its stores rather than remain in active storage mode. It is also free to devote energy to repair, rather than stockpiling fat. Key for maintenance.
Another observation. I don't find that alternating IF techniques with ad libitum eating (meaning: eat whatever you want), works for me or for my patients. POWs (previously overweight people) almost uniformly have insulin issues, primarily insulin resistance. This means that when they eat carbohydrates they make a lot of insulin that doesn't work well. The insulin drives fat storage and also hunger. When POWs reintroduce carbs they must be very careful because they can develop intense hunger levels and cravings---often in the very first day! And then, how easy is it going to be to fast?? Are you nodding your head? We have all experienced this. So, for me, the idea of alternating eating whatever you want with fasting is a pipe dream. It falls into the category of a wishful thinking diet. We've gone around this block so many times! Isn't there a way we can magically just eat the the foods that are causing the problem? I believe the answer is no. Not until science develops a drug that changes the way our bodies process food.
My advice---as always---is to be your own scientist and to use experimentation and observation to try techniques that solidify your maintenance. I do believe that IF is a good one. Find some form that works for you and is effective. But stay with your basic maintenance diet at other times and don't give in to the temptation to use IF to "clean up" days of overeating or of poor-choice eating. You will find that these days quickly overwhelm your resolve to do anything healthy whatsoever.
If you are using IF modifications in your maintenance, please comment and share your techniques.