Does Intermittent Fasting Help With Healthy Weight Loss?
Intermittent fasting isn't a new concept, but over the past couple of years, it's been gaining traction as one of the most popular dieting strategies out there.
While there are many proposed benefits of intermittent fasting, like improved digestion, better sleep, and increased energy, one question that surrounds intermittent fasting is whether or not it can help with healthy weight loss and management.
Many experts—and science—seem to agree that yes, intermittent fasting can help you lose weight in a healthy way, as long as you also pay attention to the quality of the food you're eating.
What exactly is intermittent fasting?
Intermittent fasting isn't technically a diet. It's more of a strategy or a tool that you can use along with your eating plan. There are many types of intermittent fasting, but the basic idea is that you alternate set periods of time when you eat with set periods of time when you fast, or completely abstain from food.
The most common forms of intermittent fasting are:
- Time-restricted fasting (16/8 method): Time-restricted fasting involves intervals of daily fasting. Typically, someone will fast for 14 to 16 hours and then eat during an 8- to 10-hour window every day.
- Periodic fasting (5:2 Diet): Periodic fasting involves eating normally five days of the week and then fasting, consuming only about 500 to 600 calories, on the other two days. It's recommended to choose nonconsecutive fasting days.
- Alternate-day fasting: Alternate-day fasting involves alternating between fasting days and days of regular eating throughout the week. For example, you eat normally on Monday, fast on Tuesday, eat normally on Wednesday, fast on Thursday, and so on. On your fasting days, you typically eat 500 to 600 calories.
- OMAD (one meal a day): OMAD is a form of intermittent fasting where you eat only one meal each day. Generally, this means you spend 23 hours fasting and one hour eating each day.
None of the forms of intermittent fasting have restrictions on which types of food you can eat, just when you can eat.
Is intermittent fasting effective for weight loss?
Even though there are no strict rules about what you can eat, board-certified internist Vincent M. Pedre, M.D., says that when it comes to weight loss, intermittent fasting is a "tactic that almost always works when everything else has failed." You don't have to take his word for it, though. There's a lot of science that says so, too.
A 2020 review in Nutrition that compared several weight loss diet strategies reported that people who incorporated intermittent fasting lost an average of 4 to 10% of their body weight over a period of four to 24 weeks.
Another review found that 27 subjects who did intermittent fasting saw 0.8% to 13.0% weight loss from their baseline weight.
While this diet style may result in eating less, it's possible to lose weight with intermittent fasting even without changing your calorie intake. That's because unlike normal calorie restriction, intermittent fasting may also help support hormone balance, like insulin, ghrelin, and leptin, which all play a role in your hunger and metabolism. This hormonal regulation is one of the reasons most of the weight you lose—as much as 79%—with intermittent fasting is in the form of fat.
Intermittent fasting may also help improve insulin sensitivity, which can decrease inflammation, making you feel less swollen and puffy, and has positive effects on your gut health, which Pedre calls "an often-overlooked but crucial aspect of losing weight and cultivating overall health."
According to a 2017 review in Annual Review of Nutrition, fasting can also help restore a healthy circadian rhythm, which has positive effects on your gut health, your metabolism, and your sleep patterns.
What's the most effective way to try intermittent fasting for weight loss?
The 2020 review in Nutrition summarized that periodic fasting (also called the 5:2 diet) seems to be the most effective way to use intermittent fasting as a weight loss tool.
However, Pedre says he doesn't believe in one-size-fits-all approaches and the most important thing is to take your individual needs into account.
When it comes to fasting, he says, "I encourage patients to start small and gradually increase their intervals. You might start with a 12-hour window between dinner and breakfast and increase that window to 14, 16, or more hours daily over time. You can also vary it day by day—the key is making it work for you."
What are reasons someone might not lose weight while intermittent fasting?
While intermittent fasting is certainly an effective tool, it's not a miracle solution, and there are some things that might stall or prevent weight loss.
Functional medicine doctor Mark Hyman, M.D., says one mistake that can prevent you from losing weight is excessively snacking between meals and eating all day. He explains that even though there are no "rules" about what to eat when intermittent fasting, the quantity and quality of your food still matters.
You might also have trouble losing weight while intermittent fasting if:
If you fall into any of the last three categories, it doesn't mean that you can't try intermittent fasting, but you may have a harder time managing weight until you get your stress levels and hormonal problems under control.
Are there any drawbacks?
While there are lots of benefits of intermittent fasting, there are some drawbacks, too. And according to Pedre, hunger is the biggest one.
While hunger tends to diminish as your body gets used to fasting, it can be a problem in the beginning stages, he says. And sometimes that hunger can lead to overeating the wrong types of foods during your feeding windows.
However, you can combat this hunger by sticking to satisfying whole foods, like lean meats, healthy fats and oils, and lots of fiber-rich veggies, when it's time to eat, Pedre says. Avoid refined carbohydrates and sugars, which can cause blood sugar fluctuations that make hunger and cravings worse.
It can also be difficult to stick to intermittent fasting when there are changes in your schedule or nighttime social events.
But as Pedre puts it, "Life happens, and you shouldn't feel absolutely confined to any diet." During the weekends, you might want to go out with your friends or have a pancake breakfast with your kids—activities that don't normally fit into your intermittent fasting schedule—and that's OK.
Intermittent fasting can help you lose weight in a healthy way, but it's not a miracle solution. If you're eating lots of unhealthy foods or excessively snacking during your feeding windows, it can prevent weight loss and any other potential health benefits of intermittent fasting. The best approach is to combine intermittent fasting with a healthy, whole food diet.
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