This is a debate paper I wrote for a class in the fall of 2014, I thought the research was important as at the time as the topic was hotly debated. There is still some confusion among many people as to the pros and/or cons of intermittent fasting, so I felt this would make a good first blog post!
Introduction
Intermittent Fasting (IF) is a diet regiment where an individual cuts out eating for certain hours during the day, or certain days in the week, or restrict eating to one meal a day . For example, one type of intermittent fasting diet is where the dieter fasts 14 to 16 hours a day, and then eats during the other 6 to 8 hours. Unsweetened drinks are allowed such as black coffee and tea, and fasting periods can occur during sleep. Another fasting method is fasting for 24 hours twice a week, unsweetened drinks are also allowed on fasting days. A third type of diet, is where the dieter will fast for 20 hours and follow up with a single large meal each day. During the fasting period, the dieter is allowed to consume small amounts of fruits and vegetables and drink unsweetened beverages.
Proponents of this diet state that Intermittent Fasting promotes weight loss while decreasing cardiovascular disease risks, and lowers diabetes risk . Opponents of this diet state that it leads to redox imbalance, insulin receptor nitration, and glucose intolerance.
I chose this topic, as several people have recently asked me about my opinion on intermittent fasting since they know I am a dietetics student. This debate research project seemed to me like an opportune time to investigate both sides and find where my opinion lands.
Argument One: Intermittent fasting promotes weight loss and cardio-protection.
In a 2012 research, “Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women” (Klempel, et al., 2012), the authors show Intermittent Fasting along with calorie restriction can help reduce obesity and the risk for cardiovascular disease. They study design included 60 obese women (BMI 30-39.9), in the age range of 35 to 65 years old. Other than being obese, these women were otherwise healthy with no history of cardiovascular disease or cancer. At the time of the study, they were not diabetic and lived a sedentary life style 3 months prior to the study. The study was a 10 week study, with the first 2 weeks designed to be a baseline where the women were requested to eat normally and maintain their current weight. Following the baseline, the women were split into two groups of thirty. Group one was classified as IFCR-L (intermittent fasting calorie restricted liquid). This group was restricted to a liquid fasting diet for the first six days of the week, and then fasted the last day. Lunch and Breakfast were substituted with a liquid powder meal, and Dinner was a normal meal that was limited to 400 to 600 kcals. Group two was classified as IFCR-F (intermittent fasting calorie restricted food). This group was similar to the IFCR-L group, with the exception that instead of a liquid meal for Lunch and Breakfast, they consumed normal foods restricted to 240 kcals according to TLC Guidelines.
During the 8 week study, there was a 92% adherence in the IFCR-L group, and an 80% adherence in the IFCR-F group during the CR days of the week. The results from the study showed that the IFCR-L group had a weight loss of 4.1%, and the IFCR-F group had a weight loss of 2.5%. Visceral fats were reduced, but abdominal subcutaneous fat was not. Total cholesterol was reduced in both groups, as well as LDL cholesterol concentrations. HDL cholesterol concentrations were unaffected in either intervention.
With regards to coronary heart disease, blood pressure was not altered in either group following the 8 week intervention; however heart rate decreased in the IFCR-L group. Glucose and Insulin concentrations decreased in the IFCR-L group, but not in the IFCR-R group. Overall, this study shows the benefits of intermittent fasting with regards to weight loss as well as lowering cholesterol and reducing key factors in heart disease. The liquid fasting diet showed to have the greatest affect in this study.
Argument Two: Long-term effects of intermittent fasting are bad
In a 2011 study, “Long-term intermittent feeding, but not caloric restriction, leads to redox imbalance, insulin receptor nitration, and glucose intolerance” , the authors demonstrate the negative side effects of intermittent fasting. The study was conducted over the course of 8 months on Sprague-Dawley rats in 2 different time intervals. The first time interval was 4 weeks, and the rats were divided into 3 groups each with a different feeding strategy. The feeding strategies for the first segment were AL (ad libitum, or at liberty), CR (calorie restriction), and IF (intermittent fasting). The IF fasting specifically was ADF (alternate day fasting). For the long-term portion of the study, they added FR (food restriction), which was the same diet as AL but at a level of 60% intake.
At 4 weeks, and then again at 8 months rats were sacrificed after 12 hour fasting. The extracted tissues were tested for glucose levels, glucose tolerance, immunoprecipitations, and H2-O2 release. Western blot analysis was used to measure to identify the various proteins, and the statistical data analyzed using GraphPad Prism and Origin software.
The rats tested at 4 weeks showed similar results to other studies conducted on the same time frame. That is, that body weight and adipose tissue were both lower in IF, and CR when compared to AF. Additionally, at 8 months body weight and adipose tissue were still lower in IF, and CR, however the difference between AL and IF were not as great. This showed that IF was effective in weight loss as CR but reduction of adipose tissue in IF was not as effective as CR. With regards to glucose intolerance, at 4 weeks IF showed the same results as CR but at 8 months glucose intolerance was significantly more apparent in IF as AL and CR was significantly reduced. Additionally, it was shown that IF had an increased redox imbalance over all three of the other feeding paradigms, showing heavy oxidative stress. Lastly the IF rats showed alterations in insulin signaling pathways.
Conclusion
In conclusion, both sides of this debate show compelling evidence towards their position. It is important to note, that these studies are not mutually exclusive as the study that tests the long-term effects of intermittent fasting in fact reproduce the results that are found on the short-term study.
One weakness in the short-term human study was that the liquid based fasting diet was premeasured and distributed by the lab, where the food based fasting diet was prepared at home. This can be demonstrated in the 80% rate at which food based diet were able to maintain their caloric intake versus the 92% rate for the liquid diet. This could suggest a higher error ratio in food that was prepared outside the laboratory. Subsequently, this could demonstrate a real difference when the intermittent fasting diet is practiced at home instead of a lab and the results may differ. A weakness in the long-term rat study was that Sprague-Dawley rats are prone to obesity and may not represent a good human model. Furthermore, the intermittent fasting strategy in that study may not represent the best fasting strategy available, that is alternate day fasting.
I have learned a great deal from this research, and feel I have a solid understanding of the possible gains and potential caveats in intermittent fasting. At this point, it is my opinion that intermittent fasting should not be practiced by anyone with existing health conditions, and in the long run a standard calorie restricted diet may prove to be healthier and safer for all people who wish to not only lose weight but maintain their weight after the initial loss. Additionally, I think further research needs to be done on humans as to the effect of long-term intermittent fasting.
References
- Cerqueira, F. M., da Cunha, F. M., Caldeira da Silva, C. C., Chausse, B., Romano, R. L., Garcia, C. C., . . . Kowaltowski, A. J. (2011). Long-term intermittent feeding, but not caloric restriction, leads to redox imbalance, insulin receptor nitration, and glucose intolerance. Free Radical Biology & Medicine, 51(7), 1454-1460. doi:10.1016/j.freeradbiomed.2011.07.006
- Collier, R. (2013). Intermittent fasting: the next big weight loss fad. Canadian Medical Association Journal, 185(8), 321-322. doi:10.1503/cmaj.109-4437
- Klempel, M., Kroeger, C. M., Bhutani, S., Trepanowski, J. F., & Varady, K. A. (2012). Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women. Nutrition Journal, 1-9. doi:10.1186/1475-2891-11-98
