Fasting is something that people have done for centuries.
And when it makes sense — after all, cavemen didn’t wake up to have breakfast at 7 AM sharp every day. They had to go out and forage for food — and that could take a while. They might not have been able to eat until the afternoon… or even the next day!
So, in a sense, you could say it’s in our nature to fast — at least a little bit.
But unlike cavemen, we get to decide when we eat. That’s why many people still use fasting as a wellness trick.
It’s called intermittent fasting (or IF) and there are a few different ways to do it.
For example: Some people alternate “fast days” and “feed days,” where you eat one day but not the next. There are also people who SERIOUSLY restrict their calories a few days a week, but eat normally the rest of the week.
But the most popular method is the “16/8 method.” That’s when you fast for 16 hours, and fit all your eating into just 8 hours, every day. If it sounds intimidating, think of it like this… you sleep for about 8 hours a night.
So if you don’t eat for 4 hours after you wake up, and for 4 hours before you go to sleep… bam. There’s your window!
Ok, now for the two big questions: Does it work? … And, is it safe?
Well, there are pros and cons to every diet… so, here they are:
Intermittent fasting has been associated with:
Because “IF” naturally leads you to consume fewer calories, it tends to lead to weight loss. Since you don’t need to count calories, or track what you eat, IF is easy to sustain… which means it could lead to weight loss that actually lasts.1
In a study, it was shown that mice that fasted intermittently suffered less damage after a heart attack than mice that had a “regular” diet. And what’s more…2
The same study showed that the inflammatory response was much less in the IF mice. This means the mice that fasted handled the physical symptoms of stress — including pain — much better than the other mice.3
Sounds pretty good so far, right? Well, before you get ahead of yourself, there are some potential downsides…
It’s also been shown that intermittent fasting:
- May affect your blood sugar regulation (especially in women)4
- Could cause you to lose too much weight… or even gain weight!5
- Might disrupt menstruation6
So it may not be the perfect “one size fits all” solution after all.
And one more thing: Several of these studies were done on mice only… which means that the effects in humans can only be assumed. We won’t really know for sure the effect IF can have until more human trials are done.
Now, the “positive” results do look good — so far. But before the research is comprehensive, most scientists might shy away from telling you to “go for it.”7
And of course, before you start any new health routine, you should talk to your healthcare provider to see if it’s healthy for you.
At the end of the day, it’s all about what works for YOUR body.
If you think IF can help you restrict your calories in a healthy way — talk to your doctor and give it a try. But if the idea of not eating for 16 hours scares you, there’s no need to force yourself into it. After all, the best diet is one you can stick to!
1. Johnstone A. Fasting for weight loss: an effective strategy or latest dieting trend?. Int J Obes. 2014;39(5):727-733.doi:10.1038/ijo.2014.214.
2. Ahmet I. Cardioprotection by Intermittent Fasting in Rats. Circulation. 2005;112(20):3115-3121. doi:10.1161/circulationaha.105.563817.
4. Heilbronn L, Civitarese A, Bogacka I, Smith S, Hulver M, Ravussin E. Glucose Tolerance and Skeletal Muscle Gene Expression in Response to Alternate Day Fasting. Obes Res. 2005;13(3):574-581.doi:10.1038/oby.2005.61.
5. Martin B, Pearson M, Kebejian L et al. Sex-Dependent Metabolic, Neuroendocrine, and Cognitive Responses to Dietary Energy Restriction and Excess. Endocrinology. 2007;148(9):4318-4333.doi:10.1210/en.2007-0161.
7. Horne B, Muhlestein J, Anderson J. Health effects of intermittent fasting: hormesis or harm? A systematic review. Am J Clin Nutr. 2015;102(2):464-470.doi:10.3945/ajcn.115.109553.