I’m a functional medicine doctor, and this is the most common mistake I see with intermittent fasting

With well-intentioned resolutions at the forefront of everyone’s mind right now, chances are you’ve got at least one friend who says she’s going to start the new year with intermittent fasting. Or maybe it’s you who wants to try IF, having read about intermittent fasting for weight loss or getting a better sleep at night.

The eating plan—which calls for eating only during certain time periods—always seems to be part of the wellness conversation, but it’s making headlines yet again this week due to a just-released study published in the New England Journal of Medicine offering new intel on the best way to go about IF. The study suggests that instead of jumping straight into it, it’s more effective to ease into it, slowly increasing the duration and frequency of the fasting periods.

As a functional medicine doctor who is known for preaching a food-as-medicine message, Mark Hyman, MD, is used to patients asking him all sorts of IF questions—or coming to him complaining that it hasn’t worked for them. Dr. Hyman says the new information makes sense and even says IF is linked to a myriad of health benefits. “Intermittent fasting, or eating your meals within an eight hour window can be effective, especially in terms of changing unhealthy eating behaviors,” he says.

But he also says he’s seen people go about IF the wrong way, too. “I think people get caught up in the terminology of it, not knowing what intermittent fasting really is,” Dr. Hyman says. “If you think about it, having your last meal by 9 p.m. and not eating again until 10 a.m. is a version of IF—that’s why the morning meal is called ‘breakfast’; you’re breaking a fast. But if you fast from 9 p.m. to 10 a.m. and then essentially eat all day, snacking between meals, well, you’re not going to see the benefits.”

In other words, fasting for a certain period of time doesn’t mean mindfulness shouldn’t come into play outside your fasting window; what you eat matters all the time. Intermittent fasting may help cut down on mindless midday or late-night snacking—part of that behavior change Dr. Hyman points out that can lead to real benefits—but it’s still important to fill up on healthy, whole foods whenever you do sit down to meal time.

It’s just another piece of evidence showing that consistently eating healthy, reasonably-portioned food is what really works—whether you’re intermittent fasting or not.

Healthy food advice that will make you feel more energized:

Here’s a whole dictionary of healthy eating plans, so you can compare them all. Plus, what a registered dietitian thinks of the ketogenic diet.