What Is Intermittent Fasting? A Detailed Beginner’s Guide

Before trying intermittent fasting, set yourself up for success by following these steps.

1. Decide on the Type

If your goal is weight loss, consider how much weight you want to lose. If it’s significant, it may make more sense to start with alternate-day fasting, though it’s more challenging, says Varady. This way, you can lose a good amount of weight in the first couple of months, which can keep motivation up. Then you may switch to time-restricted eating because it’s easier to stick with long term, she says.

2. Set Your Window

If you’re going to try time-restricted eating, you’re going to have to decide on your eating window. This can be done by preference. Some clients tell Bauer that they simply don’t need to eat in the morning, so they’ll start their eating window with lunch, have a snack, and then eat dinner. Others will scrunch all three meals into the smaller eating window.

Not ready to go all the way? Try a 12-hour fast, which is the most natural pattern for people to fall into, says Bauer. It’s not as stringent, but it stops nighttime eating, which can help you lose weight and decrease heartburn or sleep problems caused by consuming food too close to bedtime, she says.

3. Plan Fasting Days Strategically

Fasting may trigger unpleasant emotions like “hanger” (anger caused by being hungry), as well as fatigue and headache, Susie says. She recommends looking at your week and being mindful of the days that you need to perform especially well, like a day when you have a presentation for work. Those are not the days to plan a fast.

Similarly, if you have an important social function (a birthday party or another celebration), it can be really tough to fast on days when special foods are a big component. Looking ahead to fit IF around your lifestyle, not the other way around, is key to making this work for you long term.

4. Still Reach for Nutritious Foods

The belief that during feasting periods you can eat what you want is not quite true, especially if you want to do this healthfully. “Fasting is not a replacement for healthy eating,” says Bauer. To get the nutrients you need, focus on lean protein, fiber, fruits, and vegetables, as well as low-glycemic-index foods, she says. Drink plenty of water throughout the day. This will ensure that you don’t get dehydrated, which only exacerbates side effects like headache — and it’s one of the reasons you will likely urinate more frequently during intermittent fasting.

5. Slide Your Window

Again, if you’re following time-restricted eating, know that you don’t have to keep the same eating window every day. You can adjust it depending on your commitments. For example, if you have special brunch plans, then slide your window up so that you can participate — and feel happy and satisfied (not deprived) while intermittent fasting.

6. Consult a Healthcare Professional

You might have a lot of questions about whether IF is right for you, what to eat, or how to make it work in your own life, especially if you have underlying health conditions. In that case, it’s best to reach out to a registered dietitian nutritionist for guidance on how to do this safely, says Susie. You can find one in your area using the nutrition expert finder tool from the Academy of Nutrition and Dietetics.