Emily Arguello, MS, CHES - NDORI Dietetic Intern
Oct 14, 2022
What is Intermittent Fasting?
There are two types of intermittent fasting, time restricted eating and intermittent calorie restrictions. Time restricted eating involves limiting the amount of eating hours per day. This typically occurs as a 14:10 schedule, meaning 14 hours fasting and 10 hours where eating is allowed, a 16:8 schedule, or a 12:12 schedule. The second type of intermittent fasting, intermittent calorie restrictions, involves only eating 20-25% of recommended calories for a few nonconsecutive days. 4:3 and 5:2 schedules are most commonly used and involve 3 or 2 non consecutive days fasting and 4 or 5 days of regular eating.
Intermittent Fasting for Weight Loss
Much of the weight loss attributed to intermittent fasting comes from reduced calorie consumption due to more restrictive eating periods. A new systematic review out of Kansas State University sought to determine if there is a benefit to intermittent fasting compared to daily caloric restriction when the energy consumption is the same. Their systematic review found the weight loss benefits were relatively the same. Intermittent fasting did produce clinically significant weight loss when paired with calorie restriction, but not significantly more than calorie restriction alone.
Intermittent Fasting for Metabolic Risk Factors
Metabolic risk factors are conditions that increase the risk for developing chronic diseases like diabetes, cardiovascular disease, and cancers. Overweight and obesity are metabolic risk factors for many chronic diseases and often a small amount of weight loss, about 5%, can reduce risk and help to improve other risk factors. Other metabolic risk factors for chronic disease include HbA1c, Total Cholesterol, LDL, HDL, Triglycerides, Blood Pressure, and Blood Glucose. Kansas State University’s systematic review found some support for various styles of intermittent fasting improving metabolic risk factors, but many of them require additional research. Time restricted eating studies showed some reductions in total cholesterol, LDL, triglycerides, and blood pressure, but the results were not across the board. Similarly, one alternate day fasting study showed improved LDL and triglycerides. Specifically, a study on the 4:3 eating plan improved insulin sensitivity, and a study on the 5:2 eating plan reduced HbA1c levels.
Overall, intermittent fasting has shown potential for impact on weight loss and metabolic risk factors, but current research has been inconsistent and inconclusive. If intermittent fasting works for you, it can be used as a tool to help adherence to daily calorie restrictions.
Intermittent Fasting should NOT be done by those with diabetes or other blood sugar complications, those who are pregnant, or those under the age of 18.
Read the full research journal here.