Intermittent fasting (IF) is just that- cycling between periods where you eat and periods where you fast.
This eating pattern is not new. In fact, Dr. Dewey started the “no-breakfast plan” in the early 1900s encouraging patients to eat two meals per day. It has now gained popularity and has been referred to as “intermittent fasting” or “time restrictive eating”.
Eating patterns vary from 16 hour fasts with 8 hour eating window to 20 hour fasts with 4 hour eating windows and everything in between; some do alternate day fasts or extended water fasts. Some people fast in the morning, while others finish their meals earlier in the afternoon.
There is no doubt intermittent fasting may be beneficial for weight loss, reducing insulin resistance, increasing growth hormone, improving heart health, improving brain health, and optimizing the gut flora. However, just like anything intermittent fasting should be individualized.
Lets Look at some studies
Study One: Early Time Restricted Eating Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress even without Weight Loss in MEN with Prediabetes
This study randomly assigned men into one of two groups; a 6-hr feeding window with dinner before 3 PM and a 12-hr feeding window for 5 weeks.
Results/Thoughts:
- The group that stopped eating before 3 PM had improved insulin sensitivity, blood pressure, oxidative stress, and appetite independent of weight loss
- The participants ate breakfast but stopped eating several hours before bed which aids in digestion and sleep quality (although not directly measured in the study)
- The other group was still “fasting” for 12 hours which I think is good for everyone to do
- Big con- the study only looked at men
- The participants were already prediabetic so they had blood sugar issues at baseline
Study Two: Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults
This study randomly assigned obese adults into one of three groups: alternate-day fasting, calorie restriction, or no interventions for a 6 month weight loss phase and a 6 month maintenance phase.
Results/Thoughts:
- This study included females- actually the majority of the participants (86% females)
- Both the alternate fasting group and the calorie restriction group lost weight; however the weight loss was similar between the two groups.
- There was no significant differences between the groups in cardiovascular markers (blood pressure, heart rate, triglycerides, fasting glucose, fasting insulin, insulin resistance, C-reactive protein, or homocysteine) at month 6 or 12
- On the fast days participants had 25% of their energy/calorie needs and on the “feast” days they ate 125% of their energy/calorie needs; rather then truly fasting and eating normal energy/calorie needs.
- These participants were healthy, but they were obese with extra weight to lose.
This is a meta-analysis of randomized controlled trials (highest level of evidence) and they found that IF and Energy Restrictive Diets (ERD) may be helpful in lowering c-reactive protein levels (marker of inflammation) especially in overweight or obese individuals. It did not seem to make a difference in other inflammatory markers such as tumor necrosis factor-α or interleukin-6.
Another meta-analysis of randomized controlled trials that found IF and ERD can help lower LDL, triglycerides, and total cholesterol but it did not cause any changes in HDL; unlike the study referenced above.
What Do I see In Practice
It is not so straight forward. Several variables play a role on how your body will respond to intermittent fasting, such as:
- Gender
- Menstrual Cycle Timing
- Stress Levels
- Sleep Quality
- Insulin Levels
- Quality of meals
Not to mention the way you actually fast, so many options from:
- 20:4
- 16:8
- 12:12
- 14:10
- Alternate Day Fasting
- Ramadan Fasting
Each of these fasting techniques affects the body differently. I do believe we have a tendency to eat too often in the United States, keeping our insulin level elevated. This is not good for weight loss efforts, inflammation, or energy so some degree of “rest and digest” is great. However, a 16 hour fast may put too much stress on the body depending on a number of variables.
- Eating when the sun is up
- OR Getting at least 12 hours between dinner and breakfast
If you want to experiment with longer fasts, I recommend you find a Healthcare Provider (like us at STAT Wellness) that you trust to monitor your insulin, cortisol, DHEA, and thyroid levels to name a few. I see some patients tolerate longer fasts, while others end up having high cortisol (stress hormone) and low T3 (thyroid hormones). Men seem to respond well overall to longer fasts where for females it can be a little more complex- longer or more intense fasts can put too much stress on the female body (especially in the luteal phase). Remember, there is never a one size fits all.
I have also seen huge improvements in practice with what is called a Fasting Mimicking Diet, we use a product called ProLon at STAT Wellness. This is a 5 day medical fast to help with weight loss, growth hormone, insulin, and inflammation. When not breastfeeding or pregnant, I like to do this quarterly. It is not good for anyone with a history of eating disorders or who are already underweight!
Have you tried intermittent fasting? What was your experience with it? I love hearing from YOU!
xx
Kristin Oja, DNP