Intermittent fasting has become a popular weight-loss strategy. Most recently, a study in the journal Cell Metabolism showed intermittent fasting may decrease risk factors for diseases such as diabetes, cardiovascular disease and cancer. But, would it work for you? Let’s go through the basics…
Starting with their definition for “fasting” does not mean “starving”, rather significantly reducing your calories for short period of time. Doing so seems to affect your hunger and cravings over time. The idea: As your body adjusts, you become more satisfied with smaller portions. And if you eat healthier foods throughout the process, you also reduce your craving for unhealthy foods.
Different types of intermittent fasting strategies:
- 5 to 2 plan: reduce calorie intake for two days each week. On fasting days, you eat two meals of about 500 calories each. On non-fasting days, you follow a healthy diet (no junk food) but there are no calorie restrictions. You can eat foods such as lean proteins, fruits, vegetables, healthy fats, whole grains and legumes.
- Five-day-per-month fasting:
- Day one: Eat 1090 calories, comprised about 56% healthy fats, 34% carbohydrates (no refined foods) and 10% protein.
- Days two through five: Eat 725 calories, with 44% fats, 47% carbohydrates and 9% protein.
- Prolonged fasting: zero calories for 2 or more days.
- Time-restricted feeding: daily fasting intervals raging from 12 to 20 hours e.g. fasting dinner until lunch the following day and there are no guidelines on the amount or consumption of food intake.
What does the research say?
Previous research indicates fasting can have beneficial effects on patients with diabetes and cardiovascular disease, help reduce cholesterol levels in certain conditions, affect the process of inflammation and even trigger stem cell regeneration. Due to limited research studies, we still need to fully understand how and why fasting affects us.
The health effects of intermittent fasting in 3 weeks of alternate day fasting reduces body weight, body fat and plasma insulin concentrations. Those following the 2/days of 500 kcals has shown to improve insulin sensitivity and reduced abdominal fat and blood pressure, however has shown no change in growth hormone known as IGF-1 (insulin-like growth factor). High levels of IGF-1, which is a protein produced by the liver, are believed significantly to increase the risks of colorectal, breast and prostate cancer. Low levels of IGF-1 reduce those risks.
Prolonged fasting tested on mice has shown to protect the adverse effects of chemotherapy and ischemia/reperfusion-mediated toxicity and cancer progression. It has been hypothesized that the protective effects of fasting against aging and disease may partly be mediated by the reduction in IGF-1, glucose, and insulin. However, there is a risk of electrolytes/nutrient imbalances and poor compliance.
Time-restricted feeding research in humans has been associated with reduced weight, glucose and cholesterol but no changes in IGF-1 or stem cell mobilization/regeneration, meaning no cellular levels stress resistant protection.
Is intermittent fasting right for you?
Significantly reducing your total calories can be a big change and you need to ensure you are selecting a variety of balanced meals. Before you try it, speak with your healthcare professional. You also need to be sure no health concerns prevent you from fasting. People with a history of eating disorders, women who are pregnant or breastfeeding, children, and people recovering from surgery should not try it.
Raffaghello L et al. Fasting and differential chemotherapy protection in patients. Cell Cycle. 2010;9(22):4474-4476.
Brandhorst, Sebastian et al. A Periodic Diet that Mimics Fasting Promotes Multi-System Regeneration, Enhanced Cognitive Performance, and Healthspan. Cell Metabolism. 2015;22(1):86-99. Doi: : http://dx.doi.org/10.1016/j.cmet.2015.05.012
Goulin, Li et al. Intermittent Fasting Promotes White Adipose Browning and Decreases Obesity by Shaping the Gut Microbiota. Cell Metabolism. 2017;26(4):672–685.