Many women and men may turn to facial exercises or facial yoga to tighten and tone lax skin and reign in jowling, but there is not enough evidence to support these practices, a systematic review shows.

Researchers from Belgium reviewed nine published studies that were conducted in South America on effects of facial muscle exercises on facial rejuvenation. Although the authors of all studies reported positive outcomes, the research team found that the quality of the available evidence was insufficient for determining the efficacy of facial exercises for aesthetic rejuvenation.

The findings appear in the January issue of the Aesthetic Surgery Journal.

“Our review shows that there is not enough evidence to conclude whether facial exercises are effective for reducing the signs of aging,” says lead author John Van Borsel, PhD, Professor of Neurolinguistics and Logopedics at Ghent University, Ghent, Belgium, and Veiga de Almeida University, Rio de Janeiro, Brazil, in a news release. “The existing published studies were not randomized or controlled. Most lacked blinding and only used subjective measures to assess the effectiveness of treatment. We need better studies before we can draw any conclusions about the usefulness of facial exercises.”

None of the studies were randomized or controlled. Most were single case reports, small case series, or studies that used a single-group, pre-test-post-test design. Nearly every study included more than one type of exercise and most used subjective assessments. The researchers concluded that additional studies with superior designs and larger patient populations are needed—especially randomized, controlled, blinded studies evaluating a single type of exercise using objective measurements. They also noted that comparisons of different types of facial exercises are needed, as is information on the role of intensity and duration of treatment and on the effect of patient-specific variables such as age and signs of aging at onset.

“This is the first systematic review to look at the effectiveness of facial exercises for facial rejuvenation, and shows that we are really lacking evidence when it comes to the claims that facial exercises can rejuvenate the face,” says Atlanta, GA-bases plastic surgeon Foad Nahai, MD, editor-in-chief of Aesthetic Surgery Journal, in a news release. “Randomized, controlled studies are the gold standard for determining the efficacy of any procedure. Hopefully, we will see some well-designed studies in the future that can help us determine whether these claims have merit.”