Intermittent fasting exploded on the scene just a few short years ago and quickly gained popularity among celebrities and other influencers who tout the eating strategy’s long list of purported benefits. It sounds great, but common sense tells us no diet is perfect — nor is it perfect for every person.
Let’s dive into the research to find out what intermittent fasting can do… and if it’s right for you.
What is intermittent fasting and how does it work?
Though commonly referred to as a “diet,” it is, in fact, an eating pattern where by a person cycles through periods or eating and fasting. There are several ways to practice Intermittent Fasting.
1. Limited Eating Window
Often referred to as 16:8 or 18:6, this simply means you fast (don’t eat) for 16 or 18 hours each day followed by an eating window of 8 or 6 hours. You can manipulate the eating window to be whenever you choose.
For example, you can begin your fast after dinner at 7 p.m. on Monday night and continue your fast through the night and into the morning until 11 a.m. when you break your fast with a late breakfast or early lunch.
You can easily shift your eating window to earlier in the day and begin your fast earlier in the evening. The important part is that you stick to the limited eating window, regardless of the time of day.
2. Alternate Day Fasting
Also called 5:2, this pattern involves choosing two non-consecutive days each week to fast while eating a normal calorie intake the other five days of the week.
Fasting in this sense is more like strictly limiting calories. For women it is less than 500 calories on the fasting days — and for men it is less than 600 calories.
An example of this pattern is limiting your calorie intake to two small meals of less than 250-300 calories per meal on Mondays and Thursdays each week.
Eat-Stop-Eat is similar to alternate day fasting, except you avoid ALL calories for a period of 24 hours one to two times per week. This can look like eating your last meal Monday by noon and not eating again until Tuesday at noon.
4. Warrior Fast
Sometimes referred to as OMAD, this is a 20-hour fast that takes place overnight and during the day, with a four-hour eating window.
In this style of fasting, you may begin your fast at 8 p.m. the night before and not begin eating again until 4 p.m. the next day, breaking your fast with a light snack followed by a rather large nutrient-dense dinner before 8 p.m., when you begin fasting again.
With this type of fasting, you can move your eating window to any time during the day that suits you.
If you’re new to Intermittent Fasting, it’s strongly suggested that you begin with a restricted eating window each day and gradually extend your fasting periods. For example, stop eating one hour earlier than usual for one week. Then extend your morning fast by one hour until you find the right 16:8 or 18:6 time frame that fits your lifestyle.
No matter which fast you choose, it’s important to eat balanced, nutrient-rich meals during your eating windows and drink plenty of water throughout your fasting period. When your body is properly fueled, it will be able to tolerate fasting periods more easily.
What does scientific evidence show Intermittent Fasting CAN and CAN’T do for you?
The majority of research available on Intermittent Fasting has been conducted in rats. In these studies, rats have lost weight and their metabolic markers — such as blood pressure, cholesterol and blood sugar — have improved.
In clinical trials with humans, Intermittent Fasting has been shown to be safe and effective, but not more effective than any other diet . Some research shows the timing of the fast may be the most important part of the diet’s effectiveness.
Is Intermittent Fasting an effective way to prevent diabetes?
Researchers at the University of Alabama studied a small group of obese men with prediabetes . They compared a form of Intermittent Fasting called early time-restricted fasting (ETRF) — which is a 16:8 fast with an eating window between 7 a.m. and 3 p.m. — to a more typical 12-hour eating window from 7 a.m. to 7 p.m.
Both groups maintained their weight, meaning they did not gain or lose weight. But after five weeks, the ETRF group had dramatically lower insulin levels and significantly improved insulin sensitivity, as well as significantly lower blood pressure. The ETRF group also reported a significantly decreased appetite. Though this group was fasting, the participants were not starving.
What other considerations should be considered before starting Intermittent Fasting?
You should talk to your doctor before beginning Intermittent Fasting, especially if you are taking medications that need to be taken with food at a certain time each day or that can lower your blood sugar.
Intermittent Fasting can be an effective and safe method of improving your health, but jumping into a long fast without properly preparing your body is not recommended.
Ease into fasting and work your way up to longer fasting periods. Be sure to focus on nutrient dense foods that will satisfy you longer — like healthy fats, fiber, vegetables and proteins — during your eating windows.
Want to learn more about surgical and non-surgical weight loss options?
The UT Methodist Physicians Weight Management and Wellness Center provides expert guidance and a holistic, all-encompassing approach to weight loss.
-  Harris, Leanne, et al. (2018 February). Intermittent Fasting Interventions for Treatment of Overweight and Obesity in Adults: a Systematic Review and Meta-Analysis. JBI Evidence Synthesis. insights.ovid.com/crossref?an=01938924-201802000-00016
-  Sutton, Elizabeth, et al. (2018 May, 5). Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metabolism. https://www.sciencedirect.com/science/article/pii/S1550413118302535