PharmD. Candidate 2022
What is intermittent fasting?
Intermittent fasting (IF) is an eating plan that alternates between fasting for a certain number of set hours and eating for only a certain number of hours. Hence, you are eating on a regular schedule. Research demonstrates that IF is a promising method for both weight loss and displays many other long-term health benefits, when done properly and safely.
What are some positive health benefits associated with IF:
-increased energy/ boosted metabolism
Can I drink anything during my fasting time?
Water and zero-calorie beverages such as black coffee and tea are totally fine!
What are the different types of IF?
· 12:12 is a type of intermittent fasting where you fast for 12 hours, then have a 12-hour eating window
o Example: eating dinner at 6pm, then fasting until you eat breakfast at 6am the following morning (12 hour eating window)
· 16/8 is a type of intermittent fasting where you fast for 16 hours, then have a 8-hour eating window
o Example: eating dinner at 6pm, then fasting until you eat breakfast at 10am the following morning (8-hour eating window)
· 14/10 is a type of intermittent fasting where you fast for 14 hours, then have a 10-hour eating window
o Example: eating dinner at 7pm, then fasting until you eat breakfast at 9am the following morning (10 hour window)
· 5:2 method / “Twice a week Method”
o This is an approach where you cap your calories to 500 for two days of the week and on the other days there is not a restriction
o Example: Tuesdays and Thursdays, eat 500 calories. Monday, Wednesday, Friday through Sunday eat ~2000 calories
o *Zoe does not recommend this approach
· Longer periods without food, such as 24, 36, 48 and 72-hour fasting periods, are not necessarily better for you and may be dangerous
· Studies show that going too long without eating could have negative effects in the long term and encourage your body to start storing fat in response to starvation
Increased Energy/ Boosted Metabolism
· Your body has many hormones that are regulated by food stimulation and in response to stress, sleep, etc. Some of these hormones include ghrelin, leptin, and cortisol.
· Studies show that IF can help to reduce the amount of ghrelin (the “hungry” hormone) and increase leptin (the hunger “satisfying” hormone), hence you may have less of that urge to eat a large meal over time which may result in less caloric consumption.
· When IF is done INCORRECTLY, it can create more stress on your body.
· Depriving yourself of food for too long can increase levels of cortisol, the body's stress hormone, and this may lead to the opposite reaction (reduced metabolism). This is why Zoe does not recommend fasting over 16 hours.
· The key to IF is to find the proper window for eating and fasting that enables you to burn the maximum amount of fat without causing a hormone imbalance.
Improved Digestion/ Better Sleep Quality
· The whole idea here is that by getting your body into a normal eating routine, you can also adapt to a normal sleep routine through regulation of your circadian rhythms.
· Depending on the type of food eaten, it takes anywhere from 30-minutes to 3+ hours for complete digestion.
· Remember stress also negatively impacts digestion, which in turn can cause bloating.
· An easy tip to reduce bloating is to increase the amount of time between meals. Most people do best with 3-5 hours between meals.
· Check out the “Cabral Concept” podcast on intermittent fasting for more great information here: https://stephencabral.com/podcast/2090/
· With most IF regimens, it is also recommended to stop eating 2-3 hours before bedtime.
· With less energy devoted to digestion, your body can enter “deep sleep mode” and properly reset and restore metabolic functions.
· Studies show that appropriate nutrition and exercise timing are powerful tools to help the circadian rhythm and help prevent metabolic diseases.
How does IF work for weight loss?
· Ketosis is a process that happens when your body does not have constant exposure to food (fasting= time without food).
· IF stimulates ketosis naturally by tapping into fat reserves in the body and uses that “fat” for energy during the fasting window.
· Ketosis usually occurs anywhere between 10 and 14 hours for most people.
· Carbohydrates, especially quick sugars like pasta, white flours, candy, etc are quickly broken down and released into the body. If our cells do not use the energy, it is stored in our fat cell reserves. Sugar can only enter these cells with insulin, a hormone made in the pancreas. Insulin allows sugar to enter the fat cells.
· In between meals, if we do NOT snack, our insulin levels decrease. Hence, these fat cells can release the stored sugar to be used as energy.
· If someone is eating three plus meals a day and snacks, without exercising, then he or she is constantly putting their body at a caloric surplus state. The body does not have time to use the energy (take sugar out of fat cells) because there is not a long enough window to tap into the fat reserves.
· If you are still curious about this concept and want to learn more for yourself, I strongly encourage you to look up the concept of “metabolic switching” and read the following studies:
o Patterson RE, Laughlin GA, LaCroix AZ, et al. Intermittent Fasting and Human Metabolic Health. J Acad Nutr Diet. 2015;115(8):1203-1212. doi:10.1016/j.jand.2015.02.018
o de Cabo R, Mattson MP. Effects of Intermittent Fasting on Health, Aging, and Disease [published correction appears in N Engl J Med. 2020 Jan 16;382(3):298]
· Moro et al. studied participants with a higher protein intake (1.9 g/kg/d) and found that time-restricted feeding produced significant reductions in fat mass when combined with resistance training.
o Moro T, Tinsley G, Bianco A, Marcolin G, Pacelli QF, Battaglia G, Palma A, Gentil P, Neri M, Paoli A. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med.
· IF stimulates autophagy, which can enable cells to remove damaged cells. Autophagy is the body’s natural way of cleaning out damaged cells. Autophagy protects the body against infections and neurodegenerative diseases such as Alzheimer’s.
· Cells respond to IF in an adaptive response that leads to increased antioxidant defenses, DNA repair, mitochondrial biogenesis, and down-regulation of inflammation.
· This is one of the ways that IF is proposed to help reduce risk of cancer and other inflammatory disease states.
· Animal studies such as the one conducted by Goodrich and colleagues reported the average lifespan of rats increased by up to 80% with a time-restricted feeding regimen.
o Longo VD, Panda S. Fasting, Circadian Rhythms, and Time-Restricted Feeding in Healthy Lifespan. Cell Metab. 2016;23(6):1048-1059. doi:10.1016/j.cmet.2016.06.001
This type of diet is NOT for you if:
Pregnant or breastfeeding
· Children and teens under age 18
· History of diabetes or blood sugar problems
· History of eating disorders