Intermittent Fasting Diet 101: What You Need to Know

Keto and other low-carb plans are not the only popular weight-loss strategies in town! What if I told you there was another way to lose weight that did not involve food eliminations at all? If giving up occasional treats feels too restrictive to you, intermittent fasting (IF) may be a good fit.

Intermittent fasting is far from a fad diet. People have been fasting safely across the globe since the earliest antiquity. It is a common part of certain religious and spiritual events, such as Ramadan. These religious practices often have rules built in to protect the people who should not engage in fasting.

How much do you know about intermittent fasting? Today’s article will answer the following questions:

• What are the benefits of intermittent fasting?
• What are the most common types of intermittent fasting?
• Which foods are allowed on intermittent fasting and which foods are cut out?
• Who should not practice intermittent fasting?

Intermittent fasting may fit into your healthy lifestyle plan. However, it is critical that you get the information you need to do it safely before making changes.

Additionally, certain groups of people should not practice intermittent fasting. Do you know who they are? Be an informed consumer and protect your family by getting the facts on fasting.

Choosing intermittent fasting may support your weight loss and longevity

As a dietitian, I mostly see interest in fasting as a method for fat loss. There is some evidence that intermittent fasting may help some adults who are trying to lose weight.

For example, a systematic review and meta-analysis from 2018 found that intermittent fasting is equivalent to continuous calorie restriction for weight loss. This review looked at pseudo-randomized and randomized controlled trials of overweight and obese adults. Both sporadic and continuous energy restrictions were more effective than no treatment for weight loss.

The main advantage of IF is that you don’t have to track calories or limit certain food types and macronutrients. If you are a carbohydrate-lover, you don’t have to give up bread and pasta to lose weight. This may feel like a more comfortable and more sustainable lifestyle approach to certain people.

Intermittent fasting may also have utilization as a method to get the benefits of calorie restriction that are linked to longevity. When you remove the temptations of abundant food through the creation of fasting windows, lower calorie intake may result.

If you are interested in longevity through wellness practices, I recommend aiming to achieve the following. These lifestyle factors are linked to increased healthspan:

• Not smoking
• Healthy BMI (i.e., 18.5-24.9)
• Spending at least 30 minutes each day in moderate or vigorous physical activity
• High diet quality score (as measured by the Alternative Healthy Eating Index)
• Moderate alcohol intake (typically defined as up to one drink per day for women, and up to two for men)

Do you have all five of these factors? If the answer is no, you are certainly not alone. Most adults living in the United States do not meet all five.

If fasting helps you get to a healthy BMI, that may be an additional reason this approach aids in longevity. However, keep in mind that the other factors listed above are also crucial to your total wellness.

You’re more likely to have success if you pick the IF method that fits your life

There are many different types of IF; each is based on the timing of the feeding and fasting windows. The safest and most efficient types of fasting may also be called “time-restricted feeding.” In time-restricted nutrition, a person limits their feeding window to a certain number of hours per day.

Some types of fasting require people to extend their fasting window for entire days, or occasionally weeks, at a time. Extended fasting should never be undertaken without the approval and supervision of a physician. For this article, I will cover three of the most popular types of intermittent fasting only.

5:2 Fasting:

With 5:2 fasting, a person typically fasts for two days per week that are non-consecutive. A person on 5:2 may consume up to 500-600 calories on fasting days, which is well below adult energy needs. Sometimes 5:2 is called a modified fasting regimen.

When considering 5:2, realize that you will likely have to fast on a workday if you work full-time. If fasting negatively impacts your ability to work, this may not be the best strategy for you. Coworkers who are irritable due to hunger are generally not an appreciated addition to the workday!

16:8 Fasting:

One of the most common and most easily sustainable IF methods that I see is 16:8 fasting. With this method, the person has a fasting window of 16 hours, and a feeding window of 8 hours. The 16-hour fast does count the time that you are sleeping.

For some people, this strategy can be an effective way to curb late-night snacking. The 8-hour feeding window needs to be planned so that you have time to prepare meals and eat. Often, this strategy means skipping either breakfast or dinner, but you could fit three meals into this window if desired.

Some choose to shorten or extend the 8-hour feeding window. If you are interested in IF and it is safe for you, 16:8 is the approach that I would recommend. This regimen is what is most commonly meant by the term “time-restricted feeding.”

1:1 Fasting:

This type of fasting may also be called alternate day fasting. With this type of fasting, 24-hour periods of fasting alternated with 24-hour feeding windows. Unlike with 5:2, the fasting days on 1:1 often completely restrict energy-containing foods.

Significant self-reported hunger with this type of fasting may make getting through the workday a challenge. As such, alternate-day fasting may not be the best approach for most people.

There are other types of fasting protocols, as well. Ultimately, you are in the best position to determine the timing strategy that may best fit your life. This will depend on a variety of factors such as your work schedule, family mealtimes, and other commitments.

If a strategy does not feel sustainable to you, it will not be a suitable method for long-term weight loss. When you back off of a diet that you cannot maintain, the pounds are likely to pile back on. Make sure that IF fits into your lifestyle and is not just a quick and temporary fix.

Intermittent fasting will not result in weight loss if you have not created a calorie deficit. It is possible to eat an excess of calories, even with a shortened feeding window.

Thus, it is important to plan your meals in such a way that you feel full on fewer calories. Are you wondering how to accomplish that goal? I’ve got you covered in the next section.

Paying attention to the quality of your diet with IF will yield the best results

As mentioned above, intermittent fasting does not technically involve any food restrictions. Though some combine diets like keto with IF, fasting in its purest form does not eliminate any foods. If you want to eat chips or cookies within your feeding window, you may do so with IF.

The permissive nature of intermittent fasting may also be its downside. Without focusing on dietary quality, there is a risk that a person may not meet their nutrient needs. As with most diets, there is both a better and a worse way to compose meals on this plan.

It is vital that people using IF choose mostly healthier foods for the best results. Someone who is mostly eating “junk food” during their feeding window may have a difficult time achieving a caloric deficit. This can sabotage their weight loss goals, and they might also make themselves sick.

If you are interested in intermittent fasting, pack your feeding window with foods that support health. Make these foods the foundation of your diet:

• Fruits and vegetables: Aim to fill at least half your plate with fruits and vegetables. These high-volume, low-calorie foods are your best friend to help you feel satisfied with intermittent fasting.
• Lean proteins: Make sure to eat plenty of chicken, seafood, lean red meat, and legumes during your feeding window. Do not short yourself on protein; it is the most satiating macronutrient. Fatty fish is another top pick for protein, and it gives you a boost of the omega-3s DHA and EPA.
• Whole grains: Grains provide filling fiber, an assortment of B-complex vitamins, as well as key minerals like iron. Fiber is another dietary component that can help fill you up between meals.
• Low-fat dairy: Dairy foods are another source of high-quality protein. If you find that non-fat and low-fat dairy leaves you feeling unsatisfied, it is OK to choose whole milk varieties. Unsweetened yogurt, milk, and cheeses are all great options to include in your IF meal plan.
• Water: Don’t forget to stay hydrated, both during your feeding window as well as during your fasting periods. Drinking water during your fasting window is not only permitted; it is a must-do. Water infused with fruit and herbs and (non-caffeinated, unsweetened) herbal teas also count towards fluid intake.

Limit your intake of foods with added sugars, refined grains, and added oils. This will make it easier for you to create a calorie deficit for weight loss.

Heart-healthy olive oil contains 120 calories per tablespoon and should be used sparingly if your goal is fat loss. Aim to get most of your healthy fats from whole foods such as fatty fish, avocado, olives, nuts, and seeds. Some examples of fatty fish to include are salmon and sardines.

While intermittent fasting may benefit some people, it may not be right for you

Intermittent fasting is not for everyone. It can be difficult for some people to eat enough to stay healthy within a shortened period. Because of this, I don’t generally recommend intermittent fasting for people who fall into one (or more) of these categories:

• Children/adolescents
  
• People who are underweight or ill
  
• Pregnant or breastfeeding women
• People who have a history of eating disorders
• People who are taking medication that requires eating at a certain time of day
• People who are on nutrition therapy for a medical condition

As mentioned above, any fasting regimen that extends for days (or weeks) should be done under medical supervision only. There are published cases of people who got hurt by trying out extended water fasting on their own.

The growth and development of children and adolescents who undertake intermittent fasting may be negatively impacted if they cannot consume enough calories. With school schedules and extracurricular activities, this group is at high risk for undereating with IF.

Here’s an example. Imagine a teen trying to adhere to a 16:8 plan, with a feeding window from 8 am–4 pm. If school starts at 7 am, they will not be able to have breakfast.

Lunch will fall within the window. However, they will have to skip an early dinner if they participate in after-school activities. It is highly unlikely that this teen would be able to meet their entire nutrient needs during their lunch period.

Please don’t take a chance on your health if you fall into one of the above groups. The risks of intermittent fasting in these cases are very likely to outweigh the benefits.

Final thoughts on Intermittent Fasting Diet

Intermittent fasting can be a helpful strategy for weight loss, particularly for those who dislike tracking and food restrictions. However, this approach is not right for everyone. Shortening the feeding window may be particularly detrimental to those who are having trouble taking in enough calories.

It is still essential to pay attention to dietary quality even though you eliminate no foods with IF. By focusing on nutrient-rich, high-volume, low-calorie foods, you will feel satiated throughout the day. This makes it easier to create the calorie deficit that you need for weight loss.

Don’t forget to consult with your physician or a registered dietitian if you are interested in intermittent fasting. This is particularly important if you are taking a medication that is impacted by food or on nutrition therapy. Your health practitioner can help to determine whether this approach is a good fit for you.