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 fasting2. 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)5, and alternate day fasting (ADF) in which one fasts every other day2.
Intermittent fasting has yielded some tempting results – in an analysis of eight trials involving obese or 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 inflammation5.
Another study was conducted on two groups of mice (an IF group and a 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, and also exhibited more stable glucose regulation, increased insulin sensitivity, and decreased total cholesterol1.
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, prolonged studies of intermittent fasting on humans to conclude whether intermittent fasting is sustainable or beneficial in the long-term3. In trials, there tends to be a high drop-out rate and individuals are notorious for misreporting their actual caloric intake. Fasting may not be suitable for everyone, since severely decreased calorie intake may cause decreased concentration and energy levels in some individuals4. Some individuals may also feel tempted to overindulge during their feeding windows, which could lead to unhealthy bingeing behaviours3.
Although many may sing praises of the results they obtained from intermittent fasting, there is an incredible amount of variability between different people in terms of their bodies and lifestyles. As such, the most effective diets are those that can accommodate one’s unique lifestyle and are deemed to safe by a physician.
References
1. 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/
2. 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
3. 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/
4. 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
5. 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/