Although intermittent fasting (IF) might sound like yet another weight-loss fad, the strategy has been highlighted in numerous studies for its potential benefits. Also called “time-restricted eating,” IF has been associated with effects like better metabolic health, cardiovascular function, even potentially longer life.
If you’re new to IF or need a quick refresher, “intermittent fasting is an eating plan based on times you allow yourself to consume food,” Natalie Allen, R.D., an instructor of biomedical sciences at Missouri State University, previously told Runner’s World.
Popular intermittent fasting periods include:
- 16:8, a 16-hour fast, which means you have an eight-hour eating window
- 5:2, where you eat normally for five days of the week and cut your calories to 25 percent of your normal intake on two nonconsecutive days of the week
- OMAD (one meal a day), where you fast just under 24 hours—from dinner to dinner, for example—two or three times per week
Here’s the catch, though: Simply skipping breakfast is not enough to qualify as time-restricted eating, like many people may think. It takes planning, individual experimentation, and awareness of effects to ensure IF is truly working for you.
Here are some ways you might be getting it wrong, along with better tactics if you’re looking to explore intermittent fasting.
1. You don’t have a goal
If you’re just trying IF to see if it changes anything for you, that’s fine. But it’s better to have at least a few goals, such as improved sleep quality, better digestion, more consistent energy throughout the day, or changes in body composition. That way, you can have a better sense of progress.
“If you don’t know your ‘why,’ it makes it harder to adjust your plan because you won’t have anything to measure,” Fung tells Runner’s World.
2. You’re not getting enough calories—or you’re getting too many
Time-restricted eating is exactly that: You’re restricting the timeframe for eating. While it can be used along with calorie reduction, it’s not meant to be a diet in itself, says Fung.
“If you’re cutting way back on calories with fasting, then it’s likely going to backfire,” he adds. That’s because restriction has a tendency to make you swing hard in the other direction, toward a binge. When that happens often enough, you may get stuck in a yo-yo pattern that has been shown to have significantly negative effects on your health, especially on cardiovascular function.
Another potential hazard is overeating, since you’re trying to smush all your calories into a shorter timeframe. This doesn’t mean you’re in a binge every day, but you may be eating more than you’d planned because you’re concerned about being hungry during your fasting window.
Fung suggests setting your calorie intake needs first—based on factors like your age, weight, and level of activity—and then making sure you meet those calorie needs within the timeframe you’ve chosen. Chat with a registered dietitian or other medical professional if you’re not sure how many calories you should fuel with each day.
3. You’re not playing around with your timeframe
One friend raves about eating only within an eight-hour timeframe daily, but another friend eats in a 12-hour timeframe but fasts for one entire day per week—a strategy known as 7:1—and yet another says 10-hour time blocks are the way to go.
Which are you supposed to choose? The expert advice is: All of them.
“It takes time to find out what works best for you, and that involves different approaches with the understanding that if you’re not seeing benefits, you likely need another strategy,” Luiza Petre, a cardiologist who practices intermittent fasting herself—as well as advises the strategy for patients—tells Runner’s World.
The easiest way to start is with the most common variation first, she suggested, which is an 8-hour block, followed by fasting time that includes sleep. For example, breakfast at 9 a.m. and dinner at 5 p.m. and then not eating again until the next morning.
“When you’re getting started, it’s much better to see this as a long-term strategy and experiment with different schedules, rather than think you need to stick to one specific schedule because that’s what worked for a friend or family member,” Petre says.
Fung suggests trying a variation for about a week or two to give your body time to adjust. After that, you’ll know better if you have to tweak your time block to be shorter or longer. You can also try out on all-day fasting variation—like 7:1 or 5:2—to see whether that makes a difference. Along the way, it helps to record potential effects, including digestion—yes, even “output” can change—sleep quality, energy levels, and mood.
4. You’re not changing what you eat
One of the benefits of IF is that a greater focus on timing can include a pivot away from unhealthy foods you may have fallen into eating mindlessly as a late-night snack, for example. But if you’re simply moving those not-so-healthy choices to earlier in the day, it’s likely that IF won’t be much of a health booster.
Here’s the bottom line
It’s possible that intermittent fasting is not for you, and that’s okay. At some point, if you’ve tried different variations and you’re still feeling hungry or sluggish, it might be time to ditch the effort and just focus on healthy eating in general, but that doesn’t mean it will be a total loss, Fung says.
“For many people, trying this leads to a greater understanding about the effects of what they’re eating,” he says. “Even if you decide time-restricted eating doesn’t work for you, that awareness tends to remain.”