Ask Keri: It seems like everyone is talking about intermittent fasting. As an RD, do you recommend the practice?
My perspective, in a nutshell, is that the evidence on its health and weight-loss benefits are definitely compelling. However, it’s a practice that requires regimented commitment that many people will find is too difficult to fit into their lifestyle, depending on their work hours, social life, and other factors. If you’re not super diligent, you won’t be able to reap the rewards.
Here are the details you need to figure out if it’s right for you.
What is intermittent fasting?
Intermittent fasting is a broad term that covers a pattern of eating that involves a set amount of time where you don’t eat (or eat an incredibly restricted number of calories), followed by one in which you do.
The most popular version involves fitting all of your daily food consumption into an eight-hour window, followed by 16 hours of fasting. For example, you could eat between 10 a.m. and 6 p.m. every day and fast between 6 p.m. and 10 a.m. (including the hours you’re asleep). There’s also the 5:2 diet in which you split your week into five days of eating whenever you want and two days where you seriously restrict your calories—500 for women, 600 for men. (Personally, I find this one to be the easiest of the options.)
While fasting may seem extreme and irregular, proponents argue that humans actually ate this way for most of history, since hunters-gatherers ate when food was available, not at set mealtimes. Plus, fasting is an age-old part of nearly every religious tradition.
The potential benefits of intermittent fasting
The research on the health benefits of intermittent fasting is pretty interesting.
Most people try it for weight loss. Research backs up its effectiveness in patients with Type 2 diabetes. The most basic reason it can work for that purpose is that you’re simply going to eat less when restricting calories to set time periods. Fasting also reprograms your metabolism. When your body isn’t getting energy from food, it turns to its other fuel source: stored fat. By breaking down more fat and shrinking the size of fat cells, you end up with fat loss, and as a result, weight loss.
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In terms of the bigger health picture, studies link intermittent fasting to reducing markers of inflammation. They also show fasting can affect hormones, increasing production of beneficial ones like HGH (for muscle gain and fat loss) and BDNF (for cognition) while decreasing insulin levels.
Research (some in animals, some in humans) even suggests intermittent fasting’s cardiovascular and brain health benefits could extend lifespan.
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Are there risks to intermittent fasting?
So far, this all sounds really good, right? But there are, of course, caveats.
Low calorie intake always comes with risks, which is why it is important to ensure that you are getting adequate calories and proper nutrients while following this style of eating. Hunger can be a real issue, which, in turn, can lead to stress. Prolonged stress of any sort can increase inflammation in the body.
Confining yourself to a specific way of eating for a short time can also lead you down a long road of yo-yo dieting, and some argue that fasting can lead to disordered eating.
Finally, the results of some animal studies suggest intermittent fasting could affect fertility in women, so you should skip it if you’re trying to get pregnant.
The bottom line
At the end of the day, my feelings on intermittent fasting boil down to a few questions: Is it going to be doable for you? Will it make healthy eating easier or harder for you?
Some people say it simplifies their eating, but if you work long, unpredictable hours and have trouble planning meals ahead, trying to stick to a plan like this may drive you crazy. It also won’t work if you’re someone whose social life often revolves around food. Spontaneous dinner dates with friends or late-night tapas after a concert? Buh-bye.
If you do think it might work for you, make sure you’re still eating in a healthy way, which means getting all of the proper nutrients from the calories you are consuming. Focusing on real, whole foods and skipping the junk will prevent nutrient deficiencies.
If it sounds like the wrong approach, don’t beat yourself up about missing out on potential benefits. Just continue with a balanced, healthy diet and be mindful of your hunger quotient to keep overeating at bay and maintain a healthy lifestyle.