Intermittent fasting (IF), a dietary strategy that involves repeated intervals of feeding and fasting has gained popularity in the past couple of years, with proponents claiming a wide range of health benefits from insulin control to fat loss to defense against a host of diseases. The question is; is it a fad or is there sound research to back up the hype. Let’s explore!
IF, the Anecdotal
There are various permutations of intermittent fasting, with the most popular being alternate-day fasting (ADF). Promoters of this lifestyle claim that IF will increase longevity, burn fat, improve heart/lung function, improve insulin control, decrease inflammation and decrease cancer risk. One of the hallmarks of IF is it’s ability to to prevent aging symptoms of the brain and nervous system.
Many who have undertaken IF have reported feeling more “freedom” from not having to eat so often and also a sense of accomplishment and control from being able to sustain such a regimen.
There appears to be some ancient justification for intermittent fasting as some claim it is similar to how our Paleolithic ancestors ate and our systems are thus designed for such eating patterns.
IF, the research
The actual human data on IF is scarce, and no study to date (to my knowledge) has had a control group – which leaves only speculation as we don’t know if there is an advantage to daily caloric intake. The few studies that have looked at IF have shown;
- Weight loss
- Improved insulin sensitivity
- Improved fat burning (oxidation)
On the downside, studies have also shown increased hunger throughout the duration of the fast.
IF, is it for you?
According to nutrition researcher Alan Aragon, IF may benefit the following people:
- Those who have steady glucose control (not prone to hypoglycemia)
- People who are not prone to binge eating
- Those who don’t have the time/inclination to prepare and pack food
- Those who drive and/or travel a lot.
- Those who are not as concerned with gaining muscle
I would personally include those who exercise fairly vigorously more than 2-3 times per week.
- IF has the potential to impart health benefits such as improved insulin sensitivity, fat loss and prevention of mental decline.
- We don’t know if IF works better than calorie restriction, with research showing parallel benefits of calorie restriction.
- Exercise can probably replace the benefits derived from IF/calorie restriction
- IF may not be a sensible approach long-term.
- There doesn’t appear to be any physiological advantage to IF
- IF may be helpful for people trying to break a weight loss plateau.
- You still need to eat healthfully! Fasting does not negate the need for nutritious diet.
- Heilbronn, et al. Alternate day fasting in non-obese subjects: Effects on body weight, body composition and energy metabolism. Am. J. Clin. Nutr.2005 Jan;81(1):69-73.
- Varady KA, Hellerstein MK. Alternate-day fasting and chronic disease prevention: a review of human and animal trials. Am J Clin Nutr. 2007 Jul;86(1):7-13
- Heilbronn LK, Civitarese AE, Bogacka I, Smith SR, Hulver M, Ravussin E. Glucose tolerance and skeletal muscle gene expression in response to alternate day fasting. Obes Res. 2005 Mar;13(3):574-81.