Every few years, a new diet becomes popular for its promise to help people lose weight and improve their health. Sometimes, these diets are based on sound evidence, and other times they are not. Often when new diets first become popular, there is not enough data to know whether they really work.
The latest of these is intermittent fasting, which involves alternating days when you can eat anything you want and days when you eat very little. The idea is that eating very minimally at least a few days each week restricts your calories enough to lead to weight loss, and also leads to hormone changes in your body that reduce your risk of developing certain diseases, including diabetes and cancer.
When I first read about intermittent fasting, I was immediately intrigued. I like the idea of a weight-loss method that doesn’t require recording everything I eat. I’m also attracted to the idea of challenging myself to limited time periods of minimal eating. But of course, I wanted to find out whether there is any evidence on fasting.
My search identified two systematic reviews on fasting, both published last year.
The first one was published in April 2015 in the Journal of the Federation of American Societies for Experimental Biology. This review includes six studies in total that measured weight loss, blood pressure and insulin sensitivity. Taken together, the six studies reported participants lost an average of 8.9 percent of their weight after six months. All six studies also reported a reduction in participants’ blood pressure. And four of the six studies found decreased insulin concentrations. Despite the positive results, researchers concluded that the available evidence on fasting diets is limited and more research is needed.
The second systematic review, published in July 2015 in the American Journal of Clinical Nutrition, found similar results. The review identified three randomized controlled clinical trials and two observational studies. The randomized trials all found improvements in weight, blood pressure and insulin levels. And in the two observational studies, participants lowered their risk of being diagnosed with coronary artery disease and diabetes. The researchers draw a similar conclusion: While early studies show fasting could be a promising way to help people improve their health, there is not enough data yet to recommend it as a health intervention.
For my part, I am curious enough about fasting that I would like to try it for a month or two. My challenge will be to find ways to get through my fasting days without becoming too cranky or tired to deal with my three children.
On a related note, if you prefer to learn through video rather than reading, I found a YouTube Channel called Lifestyle Medicine created by a doctor-in-training who shares the evidence on health-related choices. His video on intermittent fasting does a good job of covering the topic.