By Lily Yang,
From celebrity-endorsed juice detoxes to the cabbage soup diet, fad diets have a long history of luring people into thinking that they hold the secret key to effortless and painless weight-loss. In recent years, another diet trend, called intermittent fasting, has quickly surged in popularity amongst those vying for fast and effective weight-loss.
Intermittent fasting (IF), or intermittent energy restriction, involves freely consuming all of one’s necessary caloric intake within short “feeding windows” of time in between regular periods of fasting (1). In contrast to the traditional, daily calorie counting method of dieting, many people find it easier to exert self-control by fasting for a few days in exchange for being able to eat to their heart’s content during these feeding windows. Popular intermittent fasting programs include the 5:2 diet, which allows for five consecutive days of non-restricted eating followed by two consecutive days of consuming only 20-25% of one’s regular daily caloric intake (around 500-600 calories) and alternate day fasting (ADF) in which one fasts every other day (2).
Intermittent fasting has yielded some tempting results: in an analysis of 11 studies involving obese and overweight subjects, six trials reports significantly more weight loss in the IF groups in comparison to the control groups. In addition to weight loss, subjects also had improved blood lipid profiles and decreased markers of inflammation (2).
Another study was conducted on two groups of mice (intermittent fasting vs control) that consumed the same total amount of calories over a 16-week period. At the end of the trial, the mice that were fed according to the intermittent fasting program weighed significantly less than the control group mice, and also exhibited more stable glucose regulation, increased insulin sensitivity, and decreased total cholesterol (3)
As attractive as these results may appear, it is important to remember that the results found in mice studies cannot be fully extrapolated to humans. Furthermore, there have also not been any large-scale, lengthy studies of intermittent fasting on humans to conclude whether intermittent fasting is sustainable or beneficial in the long-term (4). Some individuals may also feel tempted to overindulge during their feeding windows, which could lead to unhealthy bingeing behaviors (4). Intermittent fasting may not be suitable for everyone, since severely decreased calorie intake may cause decreased concentration and energy levels in some individuals (5).
Although many may sing praises of the results they obtained from intermittent fasting it is likely to early to conclude that this method of dieting is the preferred method for weight loss. Concerns regarding practicality, sustainability, and long-term efficacy and safety require further study. It is also important not to confuse weight loss with overall health. Before considering embarking on an intermittent fasting diet or any diet that is a stark departure from Canada’s food guide (6) one should consider their physician or registered dietician.
- Barnosky, Adrienne R. et al. “Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings,” Translational Research 164, no.4 (2014): 302-311. Accessed May 26, 2018. https://www.sciencedirect.com/science/article/pii/S193152441400200X
- Patterson, Ruth E., et al. “Intermittent Fasting and Human Metabolic Health,” J Acad Nutr Diet 115, no.8 (2015): 1203-1212. Accessed May 26, 2018. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516560/
- Anson, Michael R., et al. “Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from calorie intake,” Proc Natl Acad Sci USA 100, no.10 (2003): 6216-6220. Accessed May 26, 2018. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC156352/
- Collier, Roger. “Intermittent fasting: the science of going without,” CMAJ 185, no.9 (2013): 363-364. Accessed May 25, 2018. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3680567/
- Harvie, M., Howell, A. “Potential Benefits and Harms of Intermittent Energy Restriction and Intermittent Fasting Amongst Obese, Overweight and Normal Weight Subjects-A Narrative Review of Human and Animal Evidence,” Behav Sci (Basel) 7, no.1 (2017). Accessed May 25, 2018. https://www.ncbi.nlm.nih.gov/pubmed/28106818
- Canada’s food guide. https://www.canada.ca/en/health-canada/services/canada-food-guides.html. Accessed August 27 2018.