Intermittent fasting is a popular topic lately. There is always a new gimmick that the internet touts as the most effective way of losing weight. Fortunately for Intermittent fasting, science is on its side. In our modern society is often a rarity that someone would fast for any particular length of time. Usually when you hear of someone fasting it is because of a religious belief or practice. Even more absurd is the recent trend of juice fasts where someone consumes nothing but juice for days on end in an effort to “cleanse” the body and lose weight. Intermittent fasting is not a trend and it is here to stay.
What is it?
Intermittent fasting is pretty simple to understand. For a specified length of time you do not consume any calories and you only eat within a specific window. Two such popular methods are the Alternate Day Fasting and the 16:8 method (fasting for 16 hours and eating for 8). People who intermittent fast are generally trying to lose weight and preserve lean body mass. What does the research say about intermittent fasting?
Let’s review the study titled “Effect of short-term fasting and refeeding on transcriptional regulation of metabolic genes in human skeletal muscle”
In 2003 researchers at Yale published this paper in the journal of diabetes. They wanted to find out what really happened in the body when it reached a fasted state. The results provide a very convincing case for Intermittent fasting and weight loss.
Nine healthy males ranging from 22- 28 years old were fasted for 20h periods at a time. After the 20h period, they were all refed with a standardized meal. Two different trials were conducted so one had a refeeding meal high in carbs while the other had a meal high in fat instead. They took muscle biopsies before the fast, during the fasts, and after the meals. They combined the data between the two trials and found a very important conclusion: When the study subject’s bodies entered a fasted state, their skeletal muscles switched from primarily consuming carbs for energy to fat. The results show that the body switches to fat burning because it is attempting to preserve the glucose within the body and since it doesn’t have any food its protecting itself.
When you intermittent fast your body begins burning fat to preserve glucose in the body.
One more study will be looked at titled “Intermittent Fasting and Human Metabolic Health”
One big question that comes up is if intermittent fasting is safe to do and if it has any ill side effects. If you clicked on my link for alternate day fasting, you will notice the WebMD article states that it could be harmful. You will also notice that article was reviewed by a doctor as well. Well fortunately for us we have recent research that proves not only is intermittent fasting effective at weight loss but it comes at no risk with little to no side effects reported.
This study was published in Journal of the Academy of Nutrition and Dietetics on August 2015. This study synthesized, or combined, a ton of prior research to analyze the data as a whole to determine what the true nature of Intermittent fasting really is. The key outcomes of the study can be seen below:
- Studies in rodents and other nocturnal mammals support the hypothesis that intermittent fasting and restricting the availability of chow to the normal nighttime feeding cycle improves metabolic profiles and reduces the risk of obesity, obesity-related conditions such as nonalcoholic fatty liver disease, and chronic diseases such as diabetes and cancer.
- In healthy, normal weight, overweight, or obese adults, there is little evidence that intermittent fasting regimens are harmful physically or mentally (ie, in terms of mood).
- It appears that almost any intermittent fasting regimen can result in some weight loss. Among the 13 intervention trials included in this review, 11 (84.6%) reported statistically significant weight loss ranging from 1.3% in a crossover trial with a 2-week intervention23 to 8.0% in a 1-arm trial of 8 weeks’ duration.13
- Based on only three studies, alternate-day fasting appears to result in weight loss as well as reductions in glucose and insulin concentrations. However, this pattern may not be practical because of intense hunger on fasting days.
- Modified alternate-day fasting regimens result in reduced weight, ranging from 3.2% in comparison to a control group16 over a 12-week period to 8.0% in a one-arm trial over an 8-week period.13 There was limited and mixed evidence for reductions in insulin concentrations, improvements in lipid levels, or reductions in inflammatory factors.
- Research to date has not demonstrated that alternate-day fasting regimens produce superior weight loss in comparison to standard, continuous calorie restriction weight-loss plans.
- There are limited data from studies in human beings to support the robust rodent data regarding the positive effects of time-restricted feeding (ie, eating patterns aligned with normal circadian rhythms) on weight or metabolic health.
- There are considerable observational data on various forms of religious fasting, most of which suggest that these regimens result in transitory weight loss with mixed influence on other biomarkers.
- Data are lacking regarding the effects of intermittent fasting on other health behaviors such as diet, sleep, and physical activity.
- There are little or no published data linking intermittent fasting regimens with clinical outcomes such as diabetes, cardiovascular disease, cancer, or other chronic diseases such as Alzheimer disease.
Reviewing these two studies truly supports the hypothesis that intermittent fasting is effective at weight loss (and in particular fat loss). There are many different approaches to intermittent fasting but my personal favorite method is the 16 hour fast followed by an 8 hour eating window. I start my eating window at around 12 noon and continue eating until 8pm. Being a male at 184 pounds and 5’ 10’’, I can easily reduce my calories to 1600-1800 without enduring any pain from being hungry since the eating window provides complete satiety. For more methods and information I would also highly suggest following Jim Stoppani as he is highly regarded in the exercise and nutrition world.