Should I occasionally fast for my health?
So Doc, I’ve heard of people “fasting” for health. Is this good?
There are 38 million hits on Google for “intermittent fasting” (March, 2019). Intermittent fasting is where one goes for a time without eating food. The ratio of good human studies (16 as of 2018) to internet hits is approximately 1 study to 2 million internet hits. Personally, I think the definition of a craze is when the enthusiasm for something exceeds scientific knowledge. I think this ratio absolutely qualifies.
Are you saying fasting is bad?
No, just that we don’t have enough information to endorse fasting for the general public.
Okay. Why is starving yourself such a “craze?” It seems ironic that many suffer from starvation and we inflict it on ourselves?
One of the more popular books on the subject is “The Fast Diet” co-authored by Dr. Michael Mosley and Mimi Spencer, which popularized the 5:2 diet (The doctor in this case simply graduated from medical school but never really practiced medicine). The 5:2 diet allows one to eat normally for 5 days and the other 2 days are spent eating less than 600 calories/day. There are also several Youtube personalities that have millions of views, touting the benefits of intermittent fasting in various forms.
Wow, YouTube and books! There must be something to it, right?
I too have made a fasting recipe book. It’s huge – about 300 pages. All of them blank. If you buy the cook book, I’ll throw in my other best seller “All I Know About The Female Mind.” It also is a rather large book with many blank pages.
I think I’ll pass. Does “intermittent fasting” prevent heart attacks?
We have NO good human science that says fasting prevents heart attacks.
Well, why would anyone fast?
Easy answer – weight loss. I doubt most people do it for “health” alone. In fact, I think most people would rather have a heart attack than starve themself once or twice a week.
Okay, so will fasting help me lose weight?
Absolutely yes! Fasting every other day can help a 200 pounder lose 10 pounds in 22 days. This type of fasting is tough because you don’t lose hunger with each successive fasting period. Modified fasting, where you restrict calories on certain days, can help one lose 3.2% of body weight in 12 weeks to 8.0% body weight in 8 weeks.
Is fasting better at helping people lose weight than a “normal” diet?
How much science is there on fasting?
As of 2018, there were ONLY 16 good human studies involving a total of ONLY 558 people. The longest study was 6 months in length. There are many rat and mouse studies showing good health outcomes with different fasting patterns. Rat studies, however, are only applicable to a small group of humans – primarily politicians.
Har! Har! But there has to be an advantage to fasting diets over normal diets?
Studies consistently suggest that fasting can improve mood, improve blood tests for diabetes, and lead to more weight loss from body fat. However, blood tests for cholesterol and inflammation appear to be similar with either weight loss strategy chosen.
How do people fast?
Four ways:
1). Alternate day fasting: Eat one day and fast the next.
2). Modified fasting: Eating less than 600 calories once or several times weekly.
3). Time restricted eating: Eating only during certain hours (i.e. 3pm to 6pm).
4). Long Fasts: Going without food for more than 36 hours (I personally know people who will fast for 7 days).
So of those four fasting patterns, is there one that is better for health?
The fasting pattern that seems most promising for overall health is pattern #3 – Time restricted eating. Here’s the evidence. People who eat most of their calories between dinner and when they go to bed, have the highest levels of obesity, metabolic syndrome, and fatty liver disease. Big dinner and late-night eaters also have a 55% higher risk of heart attacks.
So we should eat most of our calories before dinner right?
Spot on. In fact, people that eat most of their calories before 5pm (<30% at dinner) have the lowest levels of inflammation and diabetes. Another study showed that adults who avoided eating between 7pm and 6am lost about one pound on a calorie-restricted diet over two weeks. Also, it’s probably a myth that skipping breakfast will help one lose weight. Furthermore, men who skip breakfast are 27% more likely to have heart attacks.
Okay, so is there a right time of the day to eat?
One interesting study compared people who were nearly diabetic. One group ate between 7am and 3pm and the second group ate from 7am to 7pm. They found that even though the groups ate the same number of calories, those that ate from 7am to 3pm improved their diabetes and had lower blood pressure.
Why is eating most of our calories for breakfast and lunch better?
Basically, there are things that our bodies do during only the day or the night. This timing is called the circadian rhythm. When we eat a lot of food before bed, it disrupts this rhythm and may lead to disease. Eating most of our calories before dinner fits right in with our body’s pattern of functioning.
Okay Doc, summarize it for me.
I don’t think there is enough science to endorse fasting to prevent heart attacks. Intermittent fasting doesn’t appear to be better than daily calorie restriction to lose weight. There’s good evidence that we should eat most of our daily calories before dinner. Dinner should be less than 30% of our daily calories and should be the last time we eat until breakfast. Just remember the figure below:
Hi Dr. Nelson,
I really enjoy reading these articles — they are very informative! Is there any way I can access all articles as I would like to read them (if possible). Thank you!
Thanks Marilyn. If you go to the homepage, all the articles are linked from the list of things to do/don’t to prevent a heart attack.