Intermittent fasting also doesn't lead to eating disorders or slow down a person's metabolism, said Krista Varady, an associate professor of nutrition at the University of Illinois, Chicago, who has been studying fasting for 12 years. She's the co-author of a recent study that found obese people who followed the 16:8 fasting regimen for three months modestly lost weight and lowered their blood pressure without feeling hungry or deprived.
Varady dabbles with intermittent fasting herself, typically for a few weeks after the holidays to lose a few pounds. The 16:8 plan is less intense than the other plans, but if she wants a more rapid weight loss, she'll opt for alternate day fasting.
"The first five fast days are pretty tricky, but once your body gets adjusted to that kind of up-down pattern of eating, it actually gets really easy," Varady told TODAY.
So how do you boost your chances of intermittent fasting success?
First things, first:
Always check with your doctor before starting a diet.
Intermittent fasting is not for everyone, including people with type 1 diabetes, pregnant women and lactating women, Varady said. People with binge eating disorder will tend to overeat during their eating window, so this type of regimen won't work for them, she added.
Consider the intermittent fasting plan right for you:
Some of the popular regimens include:
The 16:8 diet, or time-restricted feeding, where you fast for 16 hours a day, but are free to eat whatever you want in the other eight hours. Experts advise picking an eating window that lets you finish your meals fairly early, such as 10 a.m. to 6 p.m. or earlier, because your body is less efficient at putting sugar away as the day goes by.
Alternate day fasting, which means limiting yourself to 500 calories one day, then eating whatever you want the next, and then repeating that process.
The 5:2 plan, which means incorporating two non-consecutive fast days into your week, then eating normally during the other days.
Eat high-fiber foods, such as nuts, beans, fruits and vegetables, and high protein foods, including meat, fish, tofu, or nuts, during your eating window, Varady advised. Chewing high-fiber gummies can also help.
Drink lots of water. People tend to think they're hungry, when they are really just thirsty, she said.
Go for black coffee or tea, or cinnamon or licorice herbal teas. These beverages may have appetite-suppressing effects, Varady noted.
Watch less TV: "I know this sounds strange, but while you are watching TV, you are bombarded with dozens of ads for food. This can make you feel hungry, when in actuality, you are not hungry at all," she said.
Remember, being "a little hungry" is the best thing that can happen to you, wrote Madelyn Fernstrom, health and nutrition editor at NBC News, calling it a "true mind-body connection" that helps you recognize fullness.
2. When should I exercise?
When Varady and her colleagues conducted a study that combined alternate day fasting and exercise, they allowed the participants to pick whether they wanted to exercise on a feasting or fasting day, and found there was no strong preference one way or the other. But the researchers were surprised the dieters actually reported feeling more energetic on fasting days.
That being said, exercise before you eat because people get hungry about half an hour after they finish working out and may find it too hard to stick to their plan if they can't eat anything at all afterwards, Varady noted.
If you're on the 16:8 plan, exercise before or during your eating window. If you're doing alternate day fasting and are exercising on your 500-calorie day, save food for after your exercise session.
3. Is it OK to skip breakfast?
Yes, Varady said. The notion that omitting a morning meal is bad for your waistline likely began with studies sponsored by cereal companies, and most of that research looked at the effects of breakfast skipping on cognition in children, she noted: "I'm not sure how that all got translated to body weight."
Another analysis, by obesity and nutrition researcher David Allison, found there wasn't scientific data to definitively support a link between eating breakfast and weight loss, or skipping breakfast and weight gain.
4. How do I combat feelings of low energy or low focus during fasting?