There’s an all-too-familiar truth when it comes to diet fads: The more hype it gets, the more people swear by it, the less likely that it’s going to be, well, actually good for you. Sure, you might lose weight with some of them, but would a medical professional tell you that they’re healthy? Hard to say.

But then there’s intermittent fasting, the wellness fad whereby you voluntarily go without food for a set period of time — hours, or even a day — in order to improve your metabolic and cardiovascular performance. Intermittent fasting isn’t just the health-and-fitness trend du jour — it also happens to be highly recommended by doctors across the country as an effective tool for shedding weight while leaving you feeling energized. But, like any weight-loss regimen, it’s best to weigh the pros and cons of fasting first, in order to figure out whether it’s right for you.

How to Intermittent Fast

The goal of intermittent fasting is a simple one: To consume all your calories during a specific window of time. Most common restriction is called the 16:8 intermittent fast, i.e, 16-hour fasting period followed by an 8-hour eating period over the course of — you guessed it — 24 hours. 

While that might seem like an awful lot of time to go without eating, it doesn’t mean you’re not allowed to put anything in your body. For instance, over that 16-hour period, fasters are still able to drink water, black coffee, or tea — sans any sugar or creamers that would take your body out of its fasting state — so it’s not entirely bleak. And, if you’re adhering to the 16:8 fast, a lot of that downtime can be spent sleeping, since most people restrict their diet starting after dinner and before the following day’s lunch. 

Alternatively, some intermittent fasters opt for a full 24-hour fast, one or two days a week. A day without food sounds pretty hairy, no doubt, but 24-hour fasters swear by it, and doctors agree that if adherents stick to a full fast on designated fasting days, followed by zero restrictions on eating when not on a fasting day, the regimen is generally safe for most people.

The Science Behind Intermittent Fasting

So why would you ever want to restrict your diet this way? That depends. Fasting benefits those who are looking to lose weight, build muscle, or anyone who is borderline diabetic or at risk for pre-diabetes. Let’s break it down and explain each category.

Weight Loss

As previously mentioned, intermittent fasting shortens your window for eating, causing you to eat fewer meals and may lead to an overall reduction in calorie intake. But in addition to reducing calories, intermittent fasting also has hormonal and metabolic effects. “Intermittent fasting can lower insulin levels and increase growth hormone levels, thereby increasing the release of the fat-burning hormone norepinephrine (noradrenaline) to improve your metabolic rate and lead to daily calorie deficit for weight loss goals,” explains Dr. Mona Kennedy, a primary care physician and obesity medicine specialist at Forward’s San Francisco clinic. 

That said, just because you have less time during the day to get your calories in and, by proxy, positive hormonal and metabolic effects, doesn’t mean that you can pig out on pizza and chocolate cake, either. Swapping binge eating for a balanced diet is the only way to ensure that the weight you lose intermittent fasting weight stays off.

Building Muscle

Intermittent fasting isn’t just about weight loss, though. It can also lead to some significant gains, too — of muscle, that is. That’s because, in addition to those metabolic changes, fasting can also help “increase human growth hormone (HGH), sometimes as much as three times normal levels,” says Dr. Kennedy. HGH naturally facilitates fat loss and increases muscle gain in your body by promoting growth, body composition, cell repair, and increasing your metabolism.

Borderline Diabetic or at Risk for Pre-Diabetes

Got a problem with sugar? Maybe you should consider intermittent fasting, then. After all, the wellness trend has been shown to be an effective method for naturally reversing the onset of Type-2 diabetes in those who are borderline diabetic or at risk for pre-diabetes by lowering blood sugar by 3-6% and fasting insulin levels by 20-31%. In fact, it’s been shown to be so effective in this role, that some doctors have begun recommending intermittent fasting as an alternative to Metformin, a commonly prescribed diabetic medication used to control high blood sugar.

So who shouldn’t be intermittent fasting?

With all these positive health benefits, you might think that anyone can start intermittent fasting and losing weight immediately. But hold on there — intermittent fasting isn’t for everyone. “Intermittent fasting is a great way to shed some pounds, but like all things, it needs to be medically safe first. Intermittent fasting is not appropriate for people with Type-1 diabetes or Type-2 insulin-dependent diabetics, nursing mothers, or pregnant women,” warns Dr. Kennedy.

As with any weight-loss plan, get your physician’s thumbs-up before you start intermittent fasting. Your Forward primary care physician doctor can help you decide whether this weight loss plan is for you. All Forward members have access to our Healthy Heart Program, stress management programs, and our Weight Management Program, a 12-week, doctor-led weight loss clinic that can help you lose the weight—and keep it off.

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