THE BLOG
10/10/2014 01:09 pm ET Updated Dec 10, 2014

Ask JJ: Can Intermittent Fasting Help or Hurt Me?

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Dear JJ: My functional medicine doc has me doing intermittent fasting twice a week, alternated with a Paleo-type diet the other five. I lost weight at first, but then I developed insomnia. Do you find intermittent fasting helpful or harmful in the long run?

As its name suggests, intermittent fasting (IF) alternates eating with not eating. Do a quick Google search and you'll find numerous IF plans, often by bloggers enthusiastically singing its praises for fat loss, boosting immunity, and otherwise favorably impacting health.

One review found for men, IF could improve your lipid profile, reduce inflammation, lower oxidative stress, and control or prevent metabolic and cardiovascular problems.

Studies with women haven't always been so impressive. One found alternate-day fasting could actually lower glucose tolerance and potentially crash your metabolism. Several female clients tell me they've experienced diverse symptoms including anxiety, increased stress, and sleeplessness when they attempted IF.

"Women seem particularly vulnerable to the dangers of intermittent fasting, which can keep cortisol elevated when it should be tapering down and create the an undesired effect of storing fat and breaking down muscle," says Sara Gottfried, M.D., author of The Hormone Cure.

One big problem I have with IF involves breakfast, or rather, skipping this crucial meal that sets your day's metabolic tone. I find breakfast skippers eat more during the day, especially at night. They aren't eating more wild salmon and Brussels sprouts either, if you catch my drift.

Skipping meals also make you a cranky, caffeinated mess. ("Have you been around intermittent fasters?" said Gottfried. "Not fun to be around!") You're snappy, all you can think about is your next meal, and you become easily distracted by the aroma coming from your coworker's cubicle.

Whether you should try IF becomes an emphatic maybe. Your mileage will vary, but if you're convinced this could be your needle mover for fast fat loss and better health, I have a strategy to make IF less painful. "The benefits of fasting come after about 18 hours, but this doesn't mean you have to force yourself to go without food all day long," says my friend Yuri Elkaim.

Indeed, one study found mice restricted to eating only eight hours a day lost more fat and improved their health compared with mice that grazed whenever they wanted, even though both groups ate the same diet.

While that doesn't give you a free pass to eat whatever you want for eight hours, you can work that 18-hour fat-burning window into your schedule a few days each week -- as my reader's doctor recommended -- without hunger or deprivation.

Simply eat a substantial breakfast and lunch with lean protein, leafy and cruciferous vegetables, slow-release high-fiber carbs, and healthy fats. Skip dinner and resume breakfast the next morning. Considering you'll be sleeping for at least eight hours, that 18-hour fasting window becomes a piece of, um, cake.

If you've done IF, what was the most challenging part? Did you get the results you wanted? Share your thoughts below. I love your questions and read every one, so keep them coming at AskJJ@jjvirgin.com.