Intermittent fasting is making its way into weight loss conversations quite a bit lately, thanks to recent scientific research supporting its use — not to mention the number of people willing to write books about it. The idea of not eating for an entire day isn’t too appealing to everyone, but for some, the possible benefits of intermittent fasting might make it worth a shot.

Intermittent fasting is being touted as a near-miracle way to boost metabolism, reset your body, and of course lose weight. But is it really all it’s cracked up to be? Is it even safe?

Here’s everything you need to know about intermittent fasting, the possible benefits, and the theories behind each suggested schedule.

What is Intermittent Fasting?

Intermittent fasting is a pattern of eating where one chooses to refrain from eating during a portion of their day or week. Unlike most diets, there aren’t typically restrictions on what a person is allowed to eat during an intermittent fast, but rather when they’re allowed to eat.

While intermittent fasting has been a hot dieting trend as of late, it’s not at all a new concept. Fasting has been used for centuries for various reasons, including coming-of-age rituals, war preparation, and to please angry deities.

Perhaps the most famous fasts have been borne out of political protest — the Suffragettes for the right to vote and Gandhi for India’s freedom from the United Kingdom.

In the early 1900’s, it was even used to treat illnesses such as diabetes and epilepsy — and while it seems like it might be ridiculous to ask someone with diabetes to fast (and therefore drop their blood sugars), it seems we’re coming full circle there. New studies are actually being done to test this very theory, but more on that later.

Fasting has also been a part of nearly every major religion throughout the course of history, including Christianity, Islam, Judaism, Buddhism, and Hinduism. At times, fasting means simply refraining from certain foods, like how Catholics aren’t supposed to eat meat on Fridays during Lent, or how Jews don’t eat leavened bread during Passover. But other times, the fast is more all-encompassing, like when Muslims fast from sunup to sundown during Ramadan.

Is Intermittent Fasting Safe?

Intermittent fasting is generally considered safe as long as it’s done in moderation — which sounds like every other diet plan, doesn’t it?

The caution here is to make sure your body doesn’t go into starvation mode. At this point, your body is trying to store every calorie it can because it doesn’t know when you’ll eat again.

Your metabolism slows to a halt and as soon as you start eating again, your body will hang onto as much as it can, typically resulting in weight gain. This is why fasting for more than one day consecutively is not recommended by any intermittent fasting schedule.

However, before starting an intermittent fasting regimen, you should consult with your physician to make sure it’s safe for your specific health situation. For example, fasting is not recommended for pregnant or nursing women, nor for many people taking diabetes medication, or for people with a history of eating disorders.

Will Intermittent Fasting Help Me Lose Weight?

The theory that intermittent fasting causes weight loss is based on two major assumptions:

1. You don’t consume so many calories during your “normal” eating days that you negate the fasting. For example, based on the 5/2 plan: if you typically eat 2,000 calories a day, but you only eat 500 calories on each of your fasting days, you’d have to eat an additional 3,000 calories during the remaining five days to catch up.

2. Having such a small caloric intake — either on specific days of the week, or daily as with the 16/8 method — should throw your body into ketosis mode (yes, like the keto diet), which should mean your body is burning fat because it no longer finds calories from food in your body.

Therefore, if both these assumptions are true — that you’re consuming fewer calories and that your body is finding fat to burn instead of food — it’s possible you’ll lose weight. However, just as diets don’t work for everyone, intermittent fasting doesn’t work for everyone.

Some people simply cannot go such long periods of time without eating because it makes them feel too weak, too tired, or simply unfocused. There will be an adjustment period when you first begin an intermittent fasting regimen — however, if you find yourself binge eating when you finally eat, or you feel like your brain is too foggy, you may want to throw in the towel. Being stressed out (or eating an entire pint of ice cream right before your fast begins) will actually fight against your body’s ability to lose weight.

What are the Benefits of Intermittent Fasting?

Weight loss is one of the most heavily touted benefits of intermittent fasting, there are other benefits currently being studied including:

  • Though more testing must be done, studies thus far have shown that intermittent fasting may improve insulin resistance and decrease blood sugar levels.
  • Fasting may help reduce inflammation in the body. Researchers at Yale believe that when dieting or fasting, the body produces a compound that “can block a part of the immune system involved in several inflammatory disorders such as type 2 diabetes, atherosclerosis, and Alzheimer’s disease.”
  • One researcher believes fasting can help make chemotherapy treatments (and the body’s natural immune system) more effective at targeting cancer cells.
  • Intermittent fasting may help lower “bad” cholesterol, which is often linked to heart disease.

It’s very important to note that at this time, very little fasting research has been done on humans. In many cases, research in this area is still limited to animals (usually mice), so take all of these benefits (and anything else you read on the internet) with a grain of salt.

What’s the Best Intermittent Fasting Schedule?

There are various suggested schedules for intermittent fasting. During a fasting period (regardless of schedule), it’s generally acceptable to drink water, unsweetened tea, black coffee, and most other zero-calorie beverages.

The 5/2 Diet

Popularized by the book The Fast Diet, this intermittent fasting schedule is relatively simple: you eat normally five days out of the week and choose to fast the other two. However, it’s not recommended you fast two days in a row — these two days should be separated by at least one day of eating normally for reasons previously mentioned.

The 5/2 method generally recommends women eat 500 calories on their fasting day, while men eat about 600 and of course, the food you eat should be healthy. This could be a bowl of oatmeal with berries in the evening before bed or perhaps a bowl of light soup. Saving your meal for the evening may also help you sleep a bit better.

If you can’t stand the thought of not eating all day (which is totally understandable), you certainly don’t have to do it that way. You could eat a couple small meals, but remember to stick to your 500 or 600 calorie guideline.

Eating some lean meat and plenty of veggies is a good way to pack in more food without adding too many calories — as long as you’re not dipping them in a high calorie food (save the ranch dressing for your non-fasting days). But if you’re looking for a little more guidance, the writers of The Fast Diet also wrote a cookbook to help people eat more efficiently on their fasting days.

If part of your healthy lifestyle involves exercise (it should), you may find working out on your fasting days to be quite difficult, as your body may not have the calories it needs to get you through it. If you do choose to get in some physical activity, you may want to keep it light.

The 16/8 Diet

This intermittent fasting schedule (also called the Leangains protocol) is oftentimes described as being one of the easiest — unsurprisingly, because it’s also relatively lenient. Following this schedule, you’d fast for 16 hours out of every day and eat whatever you wanted during the remaining 8.

Again, like any other intermittent fast, the food you eat isn’t regulated, but the time during which you eat it is.

The most common suggestion in the 16/8 diet is that you shift your non-fasting time to be earlier in the day. The reason for this is that your metabolism and blood sugars are higher in the morning, so the food you eat will likely burn off faster. Therefore, one of the most popular non-fasting time frames is from 10:00am to 6:00pm.

However, if not eating after 6:00pm is simply too difficult (we need that last snack, too!), you could shift to a 12:00pm to 8:00pm schedule. Of course, this is assuming you work a day job. If you work the night shift, you’d need to adjust your fasting schedule accordingly so you’re eating when you’re working and stopping with a reasonable amount of time before you go to bed.

If you’re going to exercise, make sure you get that in prior to the end of your non-fasting period, as your body will need to be replenished afterward. Likewise, exercising too hard on an empty stomach may prove to be too difficult, so make sure you get a small snack in if you’re planning to do it earlier in the day.

Eat Stop Eat

This intermittent fasting schedule combines the previous two, taking the long fasting period from the 16/9 method, but allowing for fewer fasting days like the 5/2 plan. This method involves a 24-hour fast from dinner one evening to dinner the next, never for more than two days a week, and of course, never two days in a row.

Unlike the 5/2 method, guidelines state you shouldn’t consume any calories during the 24-hour period (or perhaps 20 hours if you just can’t make it the full day). You can have non-caloric beverages throughout the course of the day. And when dinner rolls around after your fasting period is over, be sure to have a pre-planned healthy meal ready to go complete with whole grains, lean protein, and lots of veggies so you don’t overeat.

As with the 5/2 method, you should avoid exercise on your fasting day.

The Warrior Diet

The Warrior Diet poses perhaps the most difficult intermittent fasting schedule of the four listed here: you fast for 20 hours of each day and eat one large meal every night. This is most similar to the 16/8 diet, but of course, there is a longer period of time during which you’d have to fast on the Warrior Diet.

The biggest danger with this schedule is that you’re allowed to essentially binge on whatever you want for four hours out of the day. In addition, eating your only meal of the day too late at night could lead to slower metabolism, as you’ll be lying stationary for hours on end, as opposed to up and moving around, burning off the food.

Is Intermittent Fasting Right For You?

At Houston Weight Loss Center, we don’t typically prescribe fasting for our patients, but we recognize that it could be beneficial for some people and that they may even lose some weight. We advocate for a low-calorie diet (between 1,000 and 1,800 calories per day) filled with plenty of good carbs and lean protein.

If you choose to try intermittent fasting, make sure you’re aware of how it’s affecting the rest of your life. Some are able to adjust to fasting relatively easily. However, others find it difficult to focus on fasting days, realize they’re too tired to accomplish what they need to, or get so hungry they become irritable.

Some people report bingeing on their “normal” days at first, and while it’s normal for your body to need an adjustment period, bingeing isn’t a healthy eating habit. So if you find yourself doing so and unable to curb it, intermittent fasting may not be the best plan for you.

Regardless of the schedule you choose, it’s likely to be really difficult at the beginning. If you feel you can get through your fasting period — even if it’s a challenge — without it having negative effects on your life, it may be worth a shot. But just like every other weight loss method, intermittent fasting doesn’t work for everyone.

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