Why This Expert Doesn't Like Intermittent Fasting for Weight Loss

Photographer: Maria del RioRestrictions: Internal use only. No advertising or print.Photographer: Maria del RioEditorial and internal use approved. OK for Native and co-branded use.Photographer: Maria del RioInternal and Editorial use approved. OK for Nat
POPSUGAR Photography | Maria del Rio
POPSUGAR Photography | Maria del Rio

Intermittent fasting (IF) has become a popular way to eat and lose weight. With several different ways to do it, intermittent fasting promises to help improve digestion, shed fat, and give you more energy.

But while some people have found success on intermittent fasting, Catherine Metzgar, PhD, RD, and a member of the clinical team at Virta Health, doesn't recommend it, especially for patients like hers who have type 2 diabetes. Dr. Metzgar defines intermittent fasting as going periods of 24 hours or more without eating and pushing through periods of hunger (she's not referencing the types of intermittent fasting where you skip one or two meals a day).

"As an evidence-based registered dietitian, I can't ethically recommend fasting beyond 24 hours to lose weight," she told POPSUGAR. She said it's especially dangerous for patients who have type 2 diabetes and are taking medication to lower their blood sugar; it could lead to low blood sugar and fainting. And while there are many different ways to do IF, Dr. Metzgar said "none of these regimens that involve fasting beyond 24 hours have been proven effective in sustaining weight loss long term."

She added that since there is no scientific evidence that intermittent fasting is a sustainable way to lose weight, if she were to recommend it to her patients, "it would be more akin to running a science experiment on people instead of professional guidance."

However, there are people who don't have type 2 diabetes that may want to try intermittent fasting, and it wouldn't be as dangerous of a self-experiment with these people, especially if they are trying some of the other types of IF such as single-day fasting or the 5:2 diet.

"There are certainly people who have anecdotally had success fasting for multiple days and thrive on it, but deciding to try something based off of the stories of others and actually conferring this advice as a professional are two different things entirely," she said.

Dr. Metzgar hopes that since intermittent fasting has become so popular, more clinical trials are done to see if there are any forms of IF that can be effective weight-loss options.