How Intermittent Fasting Boosts Health
Amanda Lownes
Should you abstain from eating to improve your health? This idea seems counterintuitive, as we primarily get our macro and micronutrients as well as antioxidants and phytochemicals from food, but new research about intermittent fasting proves otherwise.
Intermittent fasting is the practice of voluntarily abstaining from food and drink for periods of time1. There are various types of intermittent fasting regimes but typically intermittent fasting can be categorized into four different types1:
- Complete alternate-day fasting—involves alternating fasting days (no food consumed) with eating days
- Modified fasting regimes—consumption of 20 to 25 percent of energy needs on scheduled fasting days, generally two nonconsecutive days per week
- Time-restricted feeding—constrains eating to specific time frames, with a prolonged fast through the night
- Religious fasting—a variety of fasting regimes undertaken for religious or spiritual purposes
So what makes the practice of not eating good for your health? There are three major hypotheses behind the benefits of intermittent fasting.
Circadian Rhythm
We've all heard that we shouldn't eat too late at night. That's because the body's metabolism and digestive hormones function best during the day1. By following along with the body's natural circadian rhythm, we can optimize the best times for eating and digesting2. The practice of intermittent fasting does just that, since we're restricting eating to the periods of time during which our circadian rhythm functions optimally for digesting and assimilating food. It is therefore hypothesized that the timing of food intake is an important determinant of human health and disease risk, and that the practice of intermittent fasting leads to improved weight regulation1.
Gastrointestinal Microbiota
Studies show that when implementing intermittent fasting, gut microbiota—the beneficial bacteria living in your gut—of people with obesity may harvest more energy from the diet, therefore influencing net energy absorption, expenditure, and storage1. Additionally, extended fasting decreases gut permeability and blunts systemic inflammation1, an underlying cause of many chronic diseases like Crohn's Disease, breast cancer3, and obesity4.
Lifestyle Behaviors
Research has found that people who fast for at least 14 hours overnight saw improvements in sleep satisfaction, energy levels, and feeling full at bedtime1. Even a one-day fast or 75 percent calorie restriction was shown to reduce caloric intake by approximately 30 percent during the subsequent three days1.
Studies are still being conducted to determine which intermittent fasting regime is most effective and the optimal fasting interval length and number of fasting days per week, but there is strong primary evidence of the benefits of intermittent fasting, overall.
If you want to try intermittent fasting, a good way to start is by making sure there are at least 14 hours between your dinner and your breakfast the following day. Even a single fasting interval in humans (e.g., overnight) can reduce concentrations of many metabolic biomarkers associated with chronic disease, such as insulin and glucose1. Fast on!
References
- Patterson R and Sears D (2017) Metabolic Effects of Intermittent Fasting. Annual Review of Nutrition. 37:371-387.
- Hatori M, Vollmers C, Zarrinpar A, DiTacchio L, Bushong EA, et al. 2012. Time-restricted feeding without reducing caloric intake prevents metabolic diseases in mice fed a high-fat diet. Cell Metab. 15:848–60
- Marinac CR, Sears DD, Natarajan L,Gallo LC, Breen CI, Patterson RE. 2015. Frequency and circadian timing of eating may influence biomarkers of inflammation and insulin resistance associated with breast cancer risk. PLOS ONE 10:e0136240
- Shen J, Obin MS, Zhao L. 2013. The gut microbiota, obesity and insulin resistance. Mol. Asp. Med. 34:39–58
About the Author
Amanda Lownes is a second year Master of Public Health in Nutritional Sciences student at the University of Michigan School of Public Health, on track to become a Registered Dietitian. She currently works as a recipe developer for food startup Mindwell Snacks, a vegetable-based snacking company. In her free time, Lownes enjoys the outdoors, playing golf, and baking.