What are the obesity experts saying about intermittent fasting?
We all know the diet fads – we see them come and go. Some are based in science, most are not. There are some diets that make sense but are too difficult to maintain. Some are just plain silly. And through them all, obesity grows.
My goal as family physician and student of obesity (personally and professionally, of course) is to research the BIG diets with medical research to back them. So, as I attended The Obesity Society‘s Obesity Week this past week, intermittent fasting was at the top of my list of lectures to attend. My Doctor Mom friends have been getting behind it and I had great weight loss results with it myself.
I read the book The Obesity Code by Dr. Jason Fung on intermittent fasting with a low-carb diet twice. He loves it – but does the true science back it? As practicing physicians, we take the research done by others and relay it into the treatment of our patients. And that research is reliant on others.
And, the other side of that, lies in research bias. When people dedicate their lives to these topics, they develop opinions. Some of the best research has come from debates in lab between researchers in the past. The big institutions that distribute this information also have their biases. In science, we try to keep it out but we know it is still there on some level. Just check out my sources below – they all have their own diet programs, despite and because, they are considered the leaders in the field.
I started by reviewing the medical institution research and opinions on intermittent fasting and here’s what I came up with ….
Harvard Nutrition Source
- “Although certain benefits of caloric restriction have been demonstrated in animal studies, similar benefits of intermittent fasting in humans have not been observed. It is unclear that intermittent fasting is superior to other weight loss methods in regards to amount of weight loss, biological changes, compliance rates, and decreased appetite.”
- “Strong recommendations on intermittent fasting for weight loss cannot be made at this time.”
- An article titled “A Surprising Update on Intermittent Fasting” from 2018 quotes research done at the University of Alabama. The key researcher actually presented her results at Obesity Week. More information on that research below.
- Based off this research, this 2018 article from Harvard Nutrition Source states, “Consider a simple form of intermittent fasting. Limit the hours of the day when you eat, and for best effect, make it earlier in the day (between 7 am to 3 pm, or even 10 am to 6 pm, but definitely not in the evening before bed).”
- “There’s simply not enough research (yet) to support or debunk this trend, and shortening your eating window may make it difficult to get the vitamins and minerals you need.”
- “Athletes especially may find it difficult to fuel and refuel appropriately for an active lifestyle.”
- “The bottom line with IF? Although the jury is still out and long-term effects are still being studied, it’s crucial to eat a healthy, well-balanced diet while following IF.”
I attended the Mayo Clinic 19th Annual Health and Wellness conference this fall and intermittent fasting was barely discussed. Obesity Week was another story.
Two key researchers, Dr. Frank Scheer from Harvard Medical School, and Dr. Courtney Peterson from the above mentioned University of Alabama both spoke on the effects of the timing of eating on weight loss and obesity-related medical conditions.
What’s Meal Timing Got To Do With It?
We know that changing what you eat will help with weight loss but how does when you eat contribute to it?
In his lecture, Dr. Scheer focused on the biggest changes in our eating schedules accompanying the drastic increase in obesity rates. And there have been some. Night-shift working has increased as have eating later, lights in the rooms at night from electronics, jet lag from increased travel, and sleep disorders like sleep apnea.
And it turns out that eating at times when your melatonin, or natural sleep hormone, levels are high does result in increased weight gain as well as increased insulin, the hormone that promotes fat production, levels.
It makes sense – eating at a time when your body is preparing for sleep can’t be good. And we know that night shift workers are at increased risk for obesity and obesity-related diseases.
What Do The Biggest Studies on Intermittent Fasting Show?
As stated above, studies on fasting are relatively new and have been small in size. Until recently. Dr. Courtney Peterson from the University of Alabama has conducted many of the recent large-scale studies on the topic and found interesting results.
Dr. Peterson suggests a few surprising results from her research:
- Time restricted feeding or eating, meaning fasting from 12 hours a day to 16 hours a day, shows significant benefits in decreasing food intake, decreasing body weight, improving insulin sensitivity and decreasing insulin levels, and potentially extending lifespan.
- Time restricted feeding shows the best results when eating occurs earlier in the day. (see above results on circadian rhythm)
- Eating between 10-6pm produced the best results especially if the largest meal was mid-afternoon. Eating later was not beneficial. The length of fasting did affect results and was not as beneficial at 12 hours as if done longer.
- Time restricted feeding can be done 5 out of 7 days a week and produce the same results as every day.
What About Alternate Day Fasting?
According to Dr. Peterson’s study results, alternate day fasting did not produce as impressive of results as that of time restricted eating. Dr. Stephen Anton of the University of Florida further spoke on this subject.
Dr. Anton reported studies that showed a higher loss of lean muscle mass in people choosing alternate day fasting (longer fasts a few days a week) over time restricted eating. Similar weight loss was present with both types of fasting.
What Type of Diet Accompanied the Fasting?
These trials were completed in individuals instructed to eat a regular diet while non-fasting. No special diet considerations were enforced.
As we see in so many diet recommendations, the experts are still divided on intermittent fasting. The truth remains: the best diet for you is the one you can stick with. The good news is that there are bigger trials and more promising results coming all of the time.
Simple Solution: Experts divided on intermittent fasting but trials are showing more and more potential for benefits beyond calorie restriction. Consider time restricted feeding with more than 12 hours fasting 5 days a week and eat your big meal earlier in the day for best results.
For more Blog Posts on Intermittent Fasting, check out: https://doctormome.com/post/intermittent-fasting-results-for-weight-loss/
For More Information from the experts on Intermittent Fasting, check out: Harvard: https://www.hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/intermittent-fasting/